[Federal Register Volume 67, Number 130 (Monday, July 8, 2002)]
[Rules and Regulations]
[Pages 45194-45237]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-15835]



[[Page 45193]]

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Part II





Department of Transportation





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Federal Aviation Administration



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14 CFR Parts 21, 36, and 91



Noise Certification Standards for Subsonic Jet Airplanes and Subsonic 
Transport Category Large Airplanes; Final Rule

  Federal Register / Vol. 67, No. 130 / Monday, July 8, 2002 / Rules 
and Regulations  

[[Page 45194]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21, 36, and 91

[Docket No. FAA-2000-7587 Amdt No. 21-81, 36-54 & 91-275]
RIN 2120-AH03


Noise Certification Standards for Subsonic Jet Airplanes and 
Subsonic Transport Category Large Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; requests for comments.

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SUMMARY: The FAA is amending the noise certification standards for 
subsonic jet airplanes and subsonic transport category large airplanes. 
These changes are based on the joint effort of the Federal Aviation 
Administration (FAA), the European Joint Aviation Authorities (JAA), 
and Aviation Rulemaking Advisory Committee (ARAC), to harmonize the 
U.S. noise certification regulations and the European Joint Aviation 
Requirements (JAR) for subsonic jet airplanes and subsonic transport 
category large airplanes. These changes will provide nearly uniform 
noise certification standards for airplanes certificated in the United 
States and in the JAA countries. The harmonization of the noise 
certification standards will simplify airworthiness approvals for 
import and export purposes.

DATES: Effective Date: August 7, 2002. Comments Date: Comments on 
revised 36.2 concerning the applicable noise requirements are due on or 
before September 6, 2002.

FOR FURTHER INFORMATION CONTACT: James Skalecky, AEE-100, Office of 
Environment and Energy (AEE), Federal Aviation Administration, 800 
Independence Avenue, SW., Washington, DC 20591; telephone (202) 267-
3699; facsimile (202) 267-5594; or e-mail at [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    This final rule is being adopted with prior notice and prior public 
comment. In response to a comment received during the comment period 
the FAA is proposing a change to section 36.2. Considering the degree 
of the change from what was noted in Notice No. 00-08 and the 
requirement that is being implemented, this final rule includes a 
request for comments only on revised section 36.2.
    Interested persons are invited to participate in this rulemaking by 
submitting such written data, views, or arguments as they may desire. 
Comments must include the regulatory docket or amendment number and 
must be submitted in duplicate to the address above. All comments 
received, as well as a report summarizing each substantive public 
contact with FAA personnel on this rulemaking, will be filed in the 
public docket. The docket is available for public inspection before and 
after the comment closing date.
    The FAA will consider all comments received on or before the 
closing date for comments. Late filed comments will be considered to 
the extent practicable. This final rule may be amended in light of the 
comments received.

Availability of Rulemaking Documents

    You can get an electronic copy using the Internet by taking the 
following steps:
    (1) Go to the search function of the Department of Transportation's 
electronic Docket Management System (DMS) web page (http://dms.dot.gov/search).
    (2) On the search page type in the last four digits of the Docket 
number shown at the beginning of this notice. Click on ``search.''
    (3) On the next page, which contains the Docket summary information 
for the Docket you selected, click on the document number for the item 
you wish to view.
    You can also get an electronic copy using the Internet through the 
Office of Bulemaking's web page at http://www.faa.gov/avr/armhome.htm 
or the Government Printing Offices's web page at http://www.access.gpo.gov/su_docs/aces/aces140.html.
    You can also get a copy by submitting a request to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW., Washington, DC 20591, or by calling (202) 267-9680. Make 
sure to identify the amendment number of docket number of this 
rulemaking.

Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 
1996 requires FAA to comply with small entity requests for information 
or advice about compliance with statutes and regulations within its 
jurisdiction. Therefore, any small entity that has a question regarding 
this document may contact its local FAA official, or the person listed 
under FOR FURTHER INFORMATION CONTACT. You can find out more about 
SBREFA on the Internet at our site, http://www.faa.gov/avr/arm/sbrefa.htm. For more information on SBREFA, e-mail us [email protected].

Background

Current Regulations

    Under 49 U.S.C. 44715, the Administrator of the Federal Aviation 
Administration is directed to prescribed ``standards to measure 
aircraft noise and sonic boom;...and regulations to control and abate 
aircraft noise and sonic boom.'' Part 36 of Title 14 of the Code of 
Federal Regulations contains the FAA's noise standards and regulations 
that apply to the issuance of type certificates for all types of 
aircraft. Subpart A, B, and C and appendices A, B, and C of part 36 
contain the requirements and standards and apply to subsonic jet 
airplanes and subsonic transport category large airplanes. Appendices 
A, B, and C of part 36 specify the test conditions, procedures, and 
noise levels necessary to demonstrate compliance.

Government and Industry Cooperation

    In June 1990 at a meeting of the JAA Council, which consists of JAA 
members from European countries and the FAA, the FAA Administrators 
committed the FAA to support the harmonization of U.S. regulations with 
the Joint Aviation Regulations (JAR). The JARs are developed for use by 
the European authorities that are member countries of the JAA.
    In January 1991, the FAA established the Aviation Rulemaking 
Advisory Committee to serve as a forum for the FAA to obtain input from 
outside the government on major regulatory issues facing the agency. 
The FAA tasked ARAC with noise certification issues. These issues 
involve the harmonization of 14 CFR part 36 with JAR 36, the 
harmonization of associated guidance material including equivalent 
procedures, and interpretations of the regulations. On October 17, 
1995, the ARAC established the FAR/JAR Harmonization Working Group for 
Subsonic Transport Category Large Airplanes and Subsonic Turbojet 
Powered Airplanes (60 FR 53824). The working group task included 
reviewing the applicable provisions of subparts A, B, and C, and 
appendices A, B, and C part 36, and harmonizing them with the 
corresponding applicable provisions of JAR 36. The FAA asked the 
working group to consider the current international standards and 
recommended practices, as issued under International Civil Aviation 
Organization (ICAO), Annex 16, Volume

[[Page 45195]]

1, and its associated Technical Manual, as the basis for development of 
these harmonization proposals. The working group forwarded a 
recommendation to amend part 36 to the ARAC. After due consideration, 
including a meeting open to the public on May 18, 2000, ARAC forwarded 
this recommendation, in the form of a draft NPRM, to the FAA for 
consideration.
    On July 11, 2000, the FAA published Notice No. 00-08 entitled 
``Noise Certification Standards for Subsonic Jet Airplanes and Subsonic 
Transport Category Large Airplanes'' (65 FR 42796). The FAA solicited 
comments on the proposals, which are discussed in the following 
section. This final rule is based on Notice No. 00-08.

Discussion of Comments

    Four commenters responded to Notice No. 00-08. These comments and 
the FAA responses are discussed below.

General Comments

    The Air Line Pilots Association (ALPA) comments that it had 
reviewed both the Notice of Proposed Rulemaking (NPRM) (Notice No. 00-
08) and draft Advisory Circular 36-4C (65 FR 48794). In its comments, 
ALPA compliments the FAA and JAA for pursuing the harmonization of 
noise certification standards and concurred with both documents. ALPA 
also states that certification standards are the appropriate means of 
reducing noise, and that aviation noise reduction should be 
accomplished primarily through technological advances in engine and 
aircraft design/certification, and not with the development of special 
pilot procedures.
    The Aerospace Industries Association (AIA) endorses the FAA's 
efforts to harmonize the U.S. and European regulations. The AIA also 
comments that the proposed rule would improve the compatibility of part 
36 with the noise standards prescribed in ICAO Annex 16, Volume 1. 
However, AIA also urges FAA to eliminate the language differences that 
would remain between part 36 and ICAO Annex 16 and its associated 
guidance material. The AIA identified several sections where it 
believes that these differences would cause the typical noise 
certification applicant to question whether the two standards (i.e., 
part 36 and ICAO Annex 16) have the same meaning. The AIA comments that 
these differences could make it more difficult and costly for 
applicants that might want reciprocal approvals by different 
certificating authorities.

FAA Response

    While recognizing AIA's concern about potential misinterpretations 
that might result from the language differences between part 36 and 
ICAO Annex 16, harmonization of part 36 with JAR 36 and ICAO Annex 16 
is not contingent upon these standards being identical, word for word. 
These language differences resulted primarily from the need to (1) 
ensure that the terminology used in part 36 is consistent with that 
which is commonly used in U.S. regulations, and (2) more precisely 
define several JAR 36 and ICAO Annex 16 provisions that were 
incorporated into part 36. The FAA believes that, rather than leading 
to misinterpretation, as suggested by AIA, more precise definitions of 
these regulatory provisions will result in less chance of 
misinterpretation. Accordingly, the FAA has not changed the proposed 
rule to eliminate these language differences.

Calibration

    The AIA notes the inconsistent use of the term ``changes'' in 
section A36.3.9.5 of the proposed rule, compared to ``any changes,'' 
used in section A36.3.9.7 to refer to calibration requirements.

FAA Response

    The FAA agrees. The word ``any'' has been removed from section 
A36.3.9.5.

Sound Propagation Effects on the Lateral Noise Measurement

    The AIA comments that the material in section A36.9.3.2(b)(1) 
concerning sound propagation effects on the lateral noise measurement 
would be more appropriate in section A36.9.3.2(b)(2)(ii).

FAA Response

    The FAA agrees and the material has been moved to section 
A36.9.3.2(b)(2)(ii). This text is now designated as a ``note,'' since 
it is advisory in nature. This change is also included in section 
A36.9.4.2(b)(2)(ii), which contains the same material.

Compatibility With ICAO Standards

    The AIA comments that the proposed rule preamble discussion under 
``Compatibility With ICAO Standards'' suggests that the FAA is willing 
to simply file differences between the 14 CFR part 36 noise standards 
and ICAO noise standard and maintain that status because it had not 
been possible to reach agreement on some items in the ARAC 
Harmonization Working Group. The AIA urges the FAA to review the 
proposed rule to re-assess the FAA's position on achieving full 
compatibility with ICAO noise standards. The AIA further urges that all 
items that have not been agreed upon by the Harmonization Working Group 
should be identified as technical issues to be studied and resolved by 
appropriate task groups within ICAO committee on Environmental 
Protection (CAEP) Working Group 1.

FAA Response

    Those items identified in the proposed rule as items for which the 
FAA intends to file differences were placed in that category after 
considerable review by the Harmonization Working Group indicated that 
the differences could not realistically be resolved prior to 
publication of the proposed rule. The FAA fully intends to continue to 
work toward resolution of these remaining differences, and is currently 
participating in ICAO CAEP Working Group 1 task groups that are 
addressing each of these differences.

Special Retroactive Requirements

    The AIA expresses support for the FAA's recognition of the 
incompatibility of current 14 CFR part 36, ICAO Annex 16, and JAR 36 on 
the date used in determining the applicable noise standards relative to 
the date of type certificate application. The AIA comments, however, 
that simply removing section 36.2, as proposed, would not solve the 
incompatibility problem. Further, given the text contained in ICAO 
Annex 16 (i.e., date of application for the certificate of 
airworthiness for the prototype), AIA does not view the proposed rule 
as meeting the FAA's stated intent to ``harmonize with the 
applicability designation of part 36 with that contained in section 1.7 
of ICAO Annex 16, Chapter 1.''
    The AIA comments that the proposed rule did not make clear how the 
FAA would handle the date for applicable noise standards for type 
design changes if reference to part 36 is removed from part 21.
    Further, considering the proposal to revise section 36.2, the AIA 
questions whether section A36.1.1 should continue to specify that the 
procedures used for noise certification are those in effect on the 
effective date of this final rule.

FAA Response

    The FAA agrees that removing and reserving section 36.2 and 
deferring to part 21 as proposed is not adequate to determine the 
applicable noise certification basis. Accordingly, section 36.2 has 
been retained and revised to

[[Page 45196]]

address the concerns expressed by AIA in its comment, while maintaining 
the FAA's intent to use the date of certification application as a 
basis for part 36 applicability. The heading of section 36.2 is also 
changed to ``Requirements as of date of application.'' The revisions 
made to section 36.2 are within the scope of Notice No. 00-08; the FAA 
is not proposing a new standard. The change was made because of the 
comment that was received relative to section 36.2. Given the change 
from Notice No. 00-08 in the manner in which this requirement is 
implemented, however, this final rule includes a request for comments 
on the revised section 36.2.
    The FAA recognizes that revised section 36.2 in this final rule 
does not correspond word for word with section 1.7 of ICAO Annex 16, 
Chapter 1. The FAA believes, however, that the revised section 36.2 is 
in agreement with the intent of section 1.7 to use the date of 
certification application as the basis for noise certification standard 
applicability.
    The change to section 36.2 specifies that the part 36 requirements 
applicable to a specific certification project are those in effect on 
the date of application for the new, amended, or supplemental type 
certificate. The FAA also agrees with the AIA's comment that a date 
need not be specified in section A36.1.1. Accordingly, since section 
36.2 will determine the applicable noise certification requirements, no 
date is specified in section A36.1.1.

Measurement of Airplane Noise Received on the Ground

    Transport Canada comments that the calibration adjustments of 
proposed section A36.3.9.1 be applied to the measured sound levels at 
the output of the analyzer, rather than within the analyzer, as 
permitted by the current rule. The commenter states that because the 
algorithms for adjustments are defined and pre-programmed into the 
analyzer by the applicant, the impact on the final result can be 
predicted with a high degree of accuracy. The commenter further states 
that, provided that these correction algorithms are discussed and 
agreed upon with the certificating authority, it should not make much 
difference whether they are programmed internally or applied externally 
to the analyzer. The commenter recommends that the current rule 
requirement be retained.

FAA Response

    The FAA disagrees with the comment. There have been instances in 
which certification applicants have either not applied, or have 
incorrectly applied, calibration adjustments to acoustic data. Although 
such adjustments are usually of small magnitude, their effect can be 
significant, especially when calculated noise levels are close to the 
noise level limits specified in part 36.
    As the commenter suggests, the effect of applying these adjustments 
will be the same, whether performed internally or externally to the 
analyzer. Other adjustments to acoustic data, however, such as 
microphone and system response corrections, are required to be applied 
externally to the analyzer, even though it is technically possible with 
many current systems to apply them internally.
    External application of these corrections enables the 
reconstruction of calculated noise levels from raw acoustic data, if 
such need should arise. Therefore, even though the internal or external 
application of these calibration adjustments will have the same effect, 
the requirement to apply the calibration adjustments externally to the 
analyzer will remain as proposed to enable the FAA to determine whether 
these adjustments have been applied correctly. Moreover, the 
requirement to apply these calibration adjustments externally was 
included in the revision to ICAO Annex 16 that was approved by the ICAO 
Council on June 27, 2001.

Reporting of Airplane Center of Gravity

    Transport Canada recommends that the FAA provide a more detailed 
explanation of why information on center of gravity is needed and how 
it will benefit aircraft definition for noise certification purposes.
    Airbus (U.K.) also comments that section A36.5.2.5(c), would 
require noise certification applicants to report the center of gravity 
range for each series of test runs. The commenter states that it 
already reports center of gravity in the flight manual, but notes that 
it currently reports the takeoff center of gravity as being ``mid 
center of gravity'' and the approach center of gravity as being 
``forward center of gravity.'' The commenter hopes that this reporting 
practice would continue to be sufficient and that no greater detail 
would be required.

FAA Response

    In section A36.5.2.5, the FAA proposed specific airplane 
configuration items and engine operating parameters that must be 
reported to the FAA in the applicant's noise certification compliance 
report. The FAA explained that each of the proposed configuration items 
and parameters can affect the airplane noise signature, and that the 
reporting requirements for these items and parameters already exist 
under current section A36.5, which specifies that the aircraft 
configuration and engine performance parameters relative to noise 
generation be reported.
    The FAA proposed in section A36.5.2.5(c) that the test airplane's 
center of gravity be reported. Transport Canada requests that the FAA 
provide more detail to explain why reporting is needed. In response to 
Transport Canada's comment, the airplane center of gravity is an 
example of an identifying characteristic of the airplane test 
configuration and an item that could influence measured noise levels. 
The center of gravity will affect the performance of the airplane and 
is therefore an integral part of the noise certification flight test 
and reference procedure. For example, for the approach noise 
certification, where part 36 requires that the reference airplane 
configuration be the noisiest configuration, the forward center of 
gravity position is usually associated with the noisiest airplane 
configuration. The forward center of gravity position forces the 
airplane's elevator to push down on the tail thereby increasing 
airframe drag and, in turn, the power required to maintain the required 
3 degree glideslope. Both the increase in airframe drag and required 
power result in a higher approach noise level.
    The final rule specifically identifies the requirement to report 
center of gravity. Accordingly, the current practice identified by 
Airbus (U.K.) of reporting center of gravity as ``forward'' or ``mid'' 
for each series of test runs will still be acceptable after the 
effective date of this final rule. Further, the center of gravity used 
in demonstrating compliance with part 36 is not required to be reported 
in the Airplane Flight Manual for noise certification purposes, as 
Airbus (U.K.) implies. This final rule only specifies that the center 
of gravity range must be reported in the applicant's noise 
certification compliance report.

Reporting of Propeller Pitch Angle

    Transport Canada comments on the requirement to report propeller 
pitch angle proposed in section A36.5.2.5(d). Because the pitch angle 
at which a propeller operates is a function of torque demand and 
propeller revolutions per minute (RPM) the commenter recommended that 
torque and propeller RPM be reported as a substitute for propeller 
pitch angle. The commenter stated that Stage 3 noise compliant 
turboprops generally operate on the principle of governed propeller 
speed. In other words the propeller RPM

[[Page 45197]]

is held constant by varying the pitch angle based on torque demand. The 
commenter further stated that, while torque is a measured parameter, 
propeller pitch angle is not.

FAA Response

    The FAA agrees that torque and propeller RPM are an acceptable 
substitute for propeller pitch angle. The source noise (i.e., the noise 
generated by the airplane) adjustments required by section A36.9.3.4 
can be made using torque and propeller RPM, and torque and propeller 
RPM can be more readily determined than propeller pitch angle. Engine 
torque and propeller rotational speed reporting requirements were 
proposed and reporting of these parameters is required by section 
A36.5.2.5(h)(2). Therefore, the proposed requirement to report 
propeller pitch angle has been removed in this final rule.

Adjustment of Airplane Flight Test Results

    Transport Canada comments that section A36.9.1.1 needs an 
explanatory note to identify the components that are the likely noise 
sources that must typically be addressed in accounting for the effect 
that airspeed has on source noise.

FAA Response

    The FAA agrees with the commenter's recommendation to identify the 
components that are the likely noise sources to typically be addressed 
in accounting for the effect of airspeed on source noise. This type of 
information is, however, more appropriate for inclusion in guidance 
material associated with part 36 rather than in part 36 itself. 
Therefore, information on the components to typically be addressed in 
accounting for the effect of airspeed on source noise have been 
included in Advisory Circular 36-4C, which is being published 
concurrently with this final rule.

Noise Certificates

    In the proposed rule discussion of compatibility with ICAO 
standards, the FAA stated that the agency is not authorized to issue 
Noise Certificates. The proposed rule also notes that while section 
36.1581 of part 36 requires that the certificated noise levels be 
included in the Airplane Flight Manual (AFM), the FAA does not require 
the AFM to be carried in the airplane. An operations manual that may 
not contain certificated noise levels is carried in some airplanes. The 
FAA invited comments on the extent of any problems encountered because 
noise compliance data are not on board the airplane.
    We received one comment concerning this subject. Airbus (U.K.) 
comments that it has received occasional queries from British Aircraft 
Corporation (BAC) 1-11 operators who have had difficulties with certain 
airport authorities when approved noise data have not been available. 
The commenter states that in the absence of a noise certificate, the 
AFM is the only FAA-approved manufacturer's document that is, or may 
be, available to provide substantiation of the noise levels. If the AFM 
is not carried on board, the commenter recommends that the FAA consider 
issuing noise certificates.

FAA Response

    Because only one comment was received, there is no indication that 
a widespread problem exists. The FAA, however, is continuing to pursue 
solutions that would result in sufficient noise data being carried on 
board aircraft to assist carriers in certain situations.

Noise Certification Reference Procedures

    Airbus (U.K.) comments on proposed section B36.7(c)(5). Airbus 
(U.K.) states that the landing approach certification is already done 
at a range of aircraft configurations in case specific airports need 
it.

FAA Response

    No change is made to the final rule based on this comment. The 
proposed rule did not propose to change the current section C36.9(b) 
requirement that bases the approach noise certification on the airplane 
landing configuration that is the most critical from a noise 
standpoint. The proposed rule moves the requirement from current 
section C36.9(b) to section B36.7(c)(5) to more closely align the 
formatting of part 36 with JAR 36 and ICAO Annex 16. Further, this 
requirement is consistent with that contained in JAR 36 and ICAO Annex 
16.

Noise Certification Test Procedures

    Airbus (U.K.) comments that the approach glide path angle (3 
degrees  0.5 degrees) proposed in section B36.8(e) does not 
allow for designs for steeper approaches, despite the existing use of 
steeper approaches at specific airports. The commenter further states 
that if an aircraft was now designed specifically for steeper approach 
and was not capable of the 3 degree approach it might be uncertifiable, 
or difficult to certify, for noise purposes.

FAA Response

    The proposed rule did not propose any change to the current section 
A36.5(c)(2)(ii) 3 degree approach reference glide path angle or the 
current section C36.9(c) glide path angle test tolerance. The proposed 
rule moves the current requirement for approach glide path angle from 
the current sections to sections B36.7(c)(1) and B36.8(e) to more 
closely align the formatting of part 36 with JAR 36 and ICAO Annex 16. 
The approach glide path angle requirements are also consistent with 
those contained in JAR 36 and ICAO Annex 16.
    In addition, while the 3 degree reference glide path angle is 
currently used to establish the part 36 approach noise certification 
level, part 36 requirements for noise tests have no bearing on the use 
of other glide path angles during normal operation of an airplane. The 
FAA believes, however, that a glide path angle of 3 degrees is the 
nominal glide path angle that is generally used during normal 
operations by the class of airplanes to which part 36, subpart B is 
appropriate. In the case of an airplane that is designed with steep 
approach capability such that it may not be capable of a 3 degree 
approach, the FAA may determine that part 36, subpart B is not the 
appropriate noise certification standard for that airplane. If such a 
determination were made, an appropriate noise certification basis for 
the airplane would be developed using U.S. rulemaking procedures 
including a public comment period. No change to the glide path 
requirement proposed in sections B36.7(c)(1) and B36.8(e) of the 
proposed rule is being made.

Corrections and Other Minor Changes to the Proposed Rule

    This final rule includes some corrections and other minor changes 
from the proposed rule.
    Typographical errors, word omissions, etc., that appeared in the 
proposed rule have been corrected. Incorrect section and appendix 
designations have also been corrected. For example, the change in 
appendix designation from ``C'' to ``B'' was not changed in all of the 
sections that it should have been. Corrections to terminology have been 
made. For example, in some sections of part 36 the proposed change in 
terminology from ``sideline'' to ``lateral'', or from ``turbojet'' to 
``jet'' was not carried through in all of the sections that needed to 
be changed. Errors in the section cross reference table have been 
corrected.

[[Page 45198]]

    Sections 36.1(f)(4) and 36.1(f)(6) have been changed to reflect the 
relocation of the tradeoff provision from current section C36.5(b) to 
section B36.6.
    In section 36.103(a) the reference to the ``flight test 
conditions'' of section B36.8 has been changed to ``test procedures'' 
to be consistent with the title of section B36.8.
    In section B36.4(b), the phrase ``* * * obtain a sufficient number 
* * *'' has been changed to ``* * * use a sufficient number * * *'' 
since the word ``use'' more appropriately defines the requirement of 
this section for a sufficient number of noise measurement points (i.e., 
locations) to be used in demonstrating the maximum lateral noise level.
    The title of section B36.7 has been changed from ``Noise 
certification reference procedures'' to ``Noise certification reference 
procedures and conditions'' to be consistent with the content of 
section B36.7.
    Section B36.7(b)(3) now contains reference to section B36.7(b)(2) 
rather than B36.7(b)(1). This change was made because section 
B36.7(b)(2) is a more appropriate reference to the thrust cutback 
requirements.
    The symbol ``EPNLr'' meaning ``Effective perceived noise 
level adjusted for reference conditions'', has been added to section 
A36.6. This symbol is used in section A36.9.4.3.1.
    In order to reflect the section formatting used by ICAO, the 
ambient noise requirements of proposed sections A36.4.9.11 and 
A36.3.9.12 have been adopted in this final rule as a part of a new 
section A36.3.10, ``Adjustments for Ambient Noise''. This formatting 
was used by ICAO in the amendment to ICAO Annex 16 that was approved by 
the ICAO Council on June 27, 2001.

Draft Advisory Circular 36-4C

    The FAA made draft Advisory Circular (AC) 36-4C available for 
public comment and published a notice of availability in the Federal 
Register on August 9, 2000 (65 FR 48794). In the proposed rule, the FAA 
stated that it intended to publish AC 36-4C concurrently with this 
final rule. The AIA comments that its review of the draft AC indicates 
that it encompasses much more explanation and interpretation of the 
regulatory requirements than the current ICAO Environmental Technical 
Manual guidance material, which is focused primarily on the use of 
equivalent procedures. The AIA encourages the FAA to take two important 
steps regarding AC 36-4C. As a first step, the AIA suggests that there 
is important work to be done in coordination with manufacturers for 
buy-in of the document concept before it is published, followed by 
integration of all sections of the document so that it can be easily 
used by readers and applicants. Second, the AIA suggests that the FAA 
recommend to ICAO Working Group 1 that it study the document and 
consider development of similar internationally accepted guidance 
material concerning compliance with the ICAO Annex 16 overall noise 
certification process.

FAA Response

    The FAA agrees with the AIA's observation that AC 36-4C encompasses 
more than the current ICAO Environmental Technical Manual. AC 36-4C was 
developed to provide comprehensive guidance on implementing the part 36 
noise certification standards. In meeting this objective, AC 36-4C 
covers many more subjects than the ICAO Environmental Technical Manual.
    Given that the AIA members constitute a significant segment of the 
intended users of AC 36-4C, the FAA accepted the assistance of the AIA 
in editing the draft AC to make it more useful to the intended users. 
These changes eliminated redundancies and improved the integration of 
the guidance material with its associated regulatory text. These 
changes have been incorporated into the final version of AC 36-4C, 
which is being published concurrently with this final rule.
    The FAA agrees with AIA's suggestion that the FAA recommend to ICAO 
Working Group 1 that it study the document and consider development of 
similar internationally accepted guidance material concerning 
compliance with the ICAO Annex 16 overall noise certification process. 
In fact, ICAO CAEP Working Group 1 has begun development of such a 
document under its current work program.

Synopsis of the Final Rule

    Part 36 contains noise standards for aircraft type and 
airworthiness certification. Subparts A, B, and C, and the related 
appendices A, B, and C, of part 36 prescribe noise levels and test 
procedures for subsonic jet airplanes and subsonic transport category 
large airplanes, including rules governing the issuance of original, 
amended, or supplemental type certificates.
    This final rule adopts changes to part 36 in three major 
categories. First, there are substantive changes to technical material, 
such as a revised method for demonstrating the lateral noise 
certification level for propeller-driven airplanes. These changes are 
discussed individually in this preamble. Second, there are many changes 
to regulatory text that will serve to minimize the language differences 
between part 36 and JAR 36, while having no substantive effect on the 
regulatory standards of part 36. These text changes are not 
specifically discussed in this preamble. Third, there are numerous 
changes to the section designations of current Appendices A, B, and C 
of part 36 that will more closely align part and JAR 36 formats. 
Changes in this category will have no substantive effect on the 
regulatory standards of part 36. The changes in part 36 section 
designations are shown in a tabular format that identifies current part 
36 sections and the corresponding sections of the revision. This 
redesignation table appears at the end of the section-by-section 
discussion.

Section-by-Section Discussion

    The following is a section-by-section discussion of the substantive 
changes to 14 CFR part 36 and its appendices. Throughout the final 
rule, the term ``jet'' has been used when referring to turbojet and 
turbofan engines. This changes the terminology in current part 36, 
which uses the term ``turbojet'' when referring to both turbojet and 
turbofan engines. This change will result in the same term being used 
in 14 CFR part 36 and JAR 36, when referring to turbojet and turbofan 
engines. For consistency with part 36, this change in terminology has 
also been included in the aircraft noise related sections of parts 21 
and 91. This change to parts 21 and 91 is discussed in the following 
section-by-section discussion.

Sections 21.93 and 21.183

    Section 21.93(b)(2) and section 21.183(e)(1), which pertain to the 
part 36 noise certification requirements, are revised to add the term 
``jet'' and retain the term ``turbojet powered'' when referring to 
turbojet or turbofan engines. This change is made to reflect the use of 
the term ``jet'' in part 36 and does not change the meaning of the term 
turbojet as it is used in either the noise certification related 
sections, or other sections of 14 CFR chapter 1.

Section 36.1

    This final rule removes section 36.1(d)(3). Amendments 36-10 (43 FR 
28406, June 29, 1978) should have removed this section when it 
redesignated section 36.1(d)(3) as section 36.1(d)(1)(iii).
    Section 36.1(f) and its subparagraphs are revised to incorporate 
changes in terminology, i.e., from ``takeoff'' to ``flyover,'' 
``sideline'' to ``lateral,'' and ``turbojet'' to ``jet,'' and the 
changes to

[[Page 45199]]

part 36 appendix and section designations that result from this final 
rule. Several of these changes were inadvertently omitted from the 
proposed rule, but are necessary to correctly reflect the changes in 
part 36 formatting and terminology.
    Sections 36.1(f)(4) and 36.1(f)(6) are revised to reflect the 
relocation of the tradeoff provision from current section C36.5(b) to 
Section B36.6. These changes are necessary to reflect the change in 
past 36 formatting.

Section 36.2

    The context of section 36.2, ``Special retroactive requirements'' 
is revised, and the heading of this section is changed to 
``Requirements as of date of application''. As discussed under the 
Discussion of Comments section of this preamble, this final rule 
retains and revises section 36.2, rather than removing this section, as 
proposed. Revised section 36.2 maintains the intent of the proposal 
(i.e., to base applicability on the date of certification) while 
addressing the comments submitted by the AIA.
    Current section 36.2 requires that the noise certification 
applicant show compliance with the part 36 requirements that are in 
effect on the date of certification. This provision was included in 
part 36 before the FAA had the authority to prevent the issuance of a 
type certificate for an aircraft design that did not include reasonable 
noise reduction design practices. The FAA subsequently received this 
authority under the Noise Control Act of 1972; the retroactive 
requirement contained in section 36.2 is no longer necessary. 
Therefore, this final rule revises section 36.2 to specify compliance 
with the noise certification requirements that are effective on the 
date of application for the type certificate, amended type certificate, 
or supplemental type certificate. This change will harmonize the 
applicability designation of part 36 with the intent of section 1.7 of 
ICAO Annex 16, Chapter 1. Given the change from Notice No. 00-08 in the 
manner in which this requirement is implemented, the FAA invites 
comments on revised section 36.2.

Section 36.6

    This final rule updates the incorporation by the reference form the 
new measurement requirements specified in section A36.3. These 
specifications are referred to under new section A36.3, which updates 
requirements for measurement and analysis systems to address the latest 
standards and equipment technology. Updated addresses for the 
International Electrotechnical Commission, American National Standards 
Institute, and FAA Regional Headquarters are also included in section 
36.6.

Section 36.7

    Section 36.7 is revised to incorporate changes in terminology, 
i.e., from ``takeoff'' to ``flyover,'' ``sideline'' to ``lateral,'' and 
``turbojet'' to ``jet''. Section 36.7 is also revised to reflect the 
changes to part 36 appendix and section designations that result from 
the changes adopted in this final rule. Several of these changes were 
inadvertently omitted from the proposed rule, but are included in this 
final rule to correctly reflect the changes in part 36 formatting and 
terminology.

Sections 36.101 and 36.103

    Two sections, 36.101, Noise measurement, and 36.103, Noise 
evaluation, were combined to become a new section 36.101, Noise 
measurement and evaluation. New section 36.101 reflects the combination 
of current Appendix A and Appendix B into revised Appendix A. These 
changes more closely align part 36 and JAR 36 formats without 
introducing any substantive changes. For the same reasons, section 
36.201 is redesignated as section 36.103.

Subpart C

    The text in subpart C has been reincorporated in subpart B and A 
and the title for subpart C is reserved.

Section 36.301

    Section 36.301 is revised by replacing the reference to ``Appendix 
C'' with a reference to ``Appendix B''. This revision reflects the 
changes in part 36 formatting.

Section 36.1581

    Section 36.1581 is revised to incorporate changes in terminology, 
i.e., from ``takeoff'' to ``flyover,'' ``sideline'' to ``lateral,'' and 
``turbojet'' to ``jet''. Section 36.1581 is also revised to reflect the 
appendix designation changes. The change in terminology from 
``takeoff'' to ``flyover'' and from ``sideline'' to ``lateral,'' and 
the replacing of the reference to part 36 Appendix C with a reference 
to Appendix B reflects the changes in part 36 formatting and 
terminology.

Appendix A--Aircraft Noise Measurement and Evaluation Under Sec. 36.101

    Revised Appendix A to part 36, Aircraft Noise Measurement and 
Evaluation under section 36.101 replaces current Appendices A and B. 
The revised Appendix A to part 36 was developed to maintain a section 
format consistent with JAR 36, Appendix A, and with ICAO Annex 16, 
Appendix 2. The text of JAR 36, Appendix A, mirrors ICAO Annex 16, 
Appendix 2.

Section A36.1  Introduction

    Section A36.1.2 is added to state that the noise certification 
instructions and procedures are intended to ensure uniform results and 
to permit comparison between tests of various types of aircraft 
conducted in different geographical locations.

Section A36.2  Noise Certification Test and Measurement Conditions

    Section A36.2 replaces current section A36.1. This new section 
describes the conditions under which noise certification testing is 
conducted and the measurement procedures that are required.
    The note in section A36.2.1.1 references the guidance material on 
the use of equivalent procedures contained in Advisory Circular 36-4C, 
``Noise Standards: Aircraft Type and Airworthiness Certification.'' 
Current AC 36-4B, ``Noise Certification Handbook,'' contains guidance 
material on the use of equivalent procedures. AC 36-4C revises and 
significantly changes the format and content of the advisory material 
and is not titled, ``Noise Standards: Aircraft Type and Airworthiness 
Certification.'' The FAA is issuing new AC 36-4C concurrently with this 
final rule. The AC 36-4C is referred to as ``the current advisory 
circuit for this part'' throughout the regulatory text in this final 
rule.
    Under this final rule, the material in current section A36.1(c)(1) 
is moved to section A36.2.2.2(a) and revised to remove the word 
``rain,'' since rain is included in the term ``precipitation.''
    The material in section A36.1(c)(2) is moved to section 
A26.2.2.2(b) and the minimum test temperature limit decreased from 36 
deg.F (2.2  deg.C) to 14  deg.F (-10  deg.C). The current 36  deg.F 
(2.2  deg.C) temperature limit is considered unnecessarily restrictive, 
given that no higher levels of atmospheric absorption, compared with 
those existing in the current test window, could be encountered by 
lowering the test day temperature. Under this revised minimum test 
temperature limit, testing must be conducted in conformance with the 
operational temperature limit for the noise measuring equipment used.
    In Notice No. 00-08, new section A36.2.2.2(c) did not include the 
current section A36.1(c)(3) provision that permits expanded atmospheric 
attenuation rates when the dew point

[[Page 45200]]

and dry bulb temperatures used for obtaining relative humidity are 
measured with a device which is accurate to within 0.5 
deg.C. As explained in Notice No. 00-08, the allowance for expanded 
atmospheric attenuation rates was not included because it would 
continue to be permitted as an equivalent procedure. Subsequent to the 
publication of Notice No. 00-08, however, the FAA determined that it is 
more appropriate to retain the allowance for expanded atmospheric 
attenuation rates as an alternative procedure in the rule text of part 
36. Therefore, this allowance is contained in section A36.2.2.2(c) of 
this final rule.
    In addition, the allowance for expanded atmospheric attenuation 
coefficients has been revised to be consistent with the ICAO 
Environmental Technical Manual allowance by (1) eliminating the 14 dB/
100 meter limit on the allowable extension, (2) requiring the use of 
atmospheric layering in accordance with the requirements of new section 
A36.2.2.3, and (3) adding an alternative allowance for cases where the 
peak noy values at the time of tone-corrected perceived noise level 
(PNLT) occur at frequencies of less than or equal to 400 hertz (Hz). 
The effect of this change is a further expansion of the allowable test 
weather conditions, but with the requirement that atmospheric layering 
be used.
    The requirements to obtain meteorological measurements within ``25 
minutes'' of each noise test measurement as required in current section 
A36.9(b)(3) is changed to ``30 minutes'' in section A36.2.2.2(g). 
Thirty minutes is the established international standard in ICAO Annex 
16. The FAA was unable to find a technical reason why the 
meteorological measurement time was originally set at 25 minutes. Based 
on technical and application considerations, an increment of 5 minutes 
does not constitute a substantive difference. No known technical 
criteria exist to assess this minimal time increment. This change will 
achieve harmonization by adopting a single international standard.
    Current section A36.9(d)(3) is revised and moved to section 
A36.2.2.3. This final rule changes the method used to establish layer 
depth to reflect the international standard. Current part 36 does not 
provide specific criteria for determining layer depth, except to 
require that it be no greater than 100 feet. The criteria for 
determining layer depth that is adopted by this final rule is the same 
as that used to specify the onset of required layering, i.e., under 
weather conditions where the atmospheric attenuation rate changes by 
more than 1.6 dB/1000 ft (0.5 dB/100m) over the 
sound propagation distance. Under this final rule, the minimum layer 
depth is established as 100 feet (30 meters). Thus, the layer depth 
would be 100 feet (30 meters) in cases where the atmospheric rate 
change criteria would limit the layer depth to less than 100 feet (30 
meters).

Section A36.3  Measurement of Aircraft Noise Received on the Ground

    The changes to this section update the requirements for measurement 
and analysis systems to include the latest standards and equipment 
technology. These changes were drafted by an international task group 
having years of knowledge and experience in the noise certification of 
airplanes. This task group was assembled under Working Group 1 of the 
ICAO Committee on Aviation Environmental Protection (CAEP) to draft 
changes that would update the ICAO Annex 16 requirements for 
measurement and analysis systems. On June 27, 2001, the ICAO Council 
approved the revision to ICAO Annex 16 that includes the updated 
requirements.
    The primary purpose of the international task group was to address 
considerations related to the use of digital equipment. Many of these 
considerations are addressed in the International Electro-Technical 
Commission (IEC) Standard 61265 and IEC Standard 61260. Accordingly, 
much of the pertinent text from these standards has been included in 
the requirements developed by the international task group. These IEC 
standards also reflect general improvements to instrumentation 
technology that have occurred over the past decade, although they are 
not necessarily related to the advent of digital technology. In 
addition to improvements tied to the IEC standards, several changes 
that resulted from the work of the task group are linked to general 
advancements in noise measurement instrumentation.
    Revised section A36.3 includes the following specific changes. 
Current section A36.3 does not include definitions. Section A36.3.1, 
Definitions, is added to define the terms used in section A36.3. 
Section A36.3.2, Reference environmental conditions, is added in this 
final rule to specify the performance of a measurement system.
    Section A36.3.3.2 is added and specifies anti-alias requirements 
for measurement systems that include analog-to-digital signal 
conversion.
    Section A36.3.4.1 adds a requirement that windscreen insertion loss 
not exceed 1.5 dB. Section A36.3.9.10 also limits the 
change in windscreen insertion loss calibration to 0.4 dB from the 
previous calibration.
    Sections A36.3.5.3 and A36.3.5.4 specify microphone sensitivity 
requirements only at the midband frequencies. This is a simplification 
of the current part 36 requirement contained in sections 
A36.3(c)(2)(ii) and A36.3(c)(2)(iii). The new sections also specify 
more stringent tolerances on microphone sensitivity. Typical 
microphones that are currently used in part 36 noise certification 
testing comply with this more stringent microphone sensitivity 
requirement.
    Section A36.3.6.3 adds a tolerance for frequency response of the 
measurement system.
    Section A36.3.6.4 adds a 0.5 dB tolerance for amplitude 
fluctuations of a recorded 1 kHz signal on analog tape.
    Section A36.3.6.5 adds a tolerance for amplitude linearity, at 
several specific frequencies, for the measurement system (exclusive of 
the microphone).
    Section A36.3.6.6 requires that the electronic signal level 
corresponding to the calibration sound pressure level be from 5 db to 
30 dB less than the upper boundary of the measurement system level 
range. This replaces the 10 dB requirement in current part 36, section 
A36.3(c)(3)(i).
    Section A36.3.6.8 adds a requirement for an overload indicator in 
the recording and reproducing system.
    Section A36.3.6.9 allows for measurement system attenuators to 
operate in known intervals of decibel steps, rather than in equal 
interval steps, as in current part 36 section A36.3(b)(6).
    Section A36.3.7.2(e) adds a requirement that the analyzer operate 
in real time from 50 Hz through at lease 12 kHz.
    Section A36.3.7.3 specifies IEC 61260 class 2 electrical 
performance requirements as the minimum standard for analyzers. This 
change updates the specifications for analyzers used in conjunction 
with part 36 noise certification. Section A36.3.7.3 also includes a 
note stating that IEC 61260 specifies procedures for testing one-third 
octave band analysis systems for relative attenuation, anti-aliasing 
filters, real time operation, level linearity, and filter integrated 
response (effective bandwidth). The IEC filter bandwidth adjustment 
method requires that the adjustment be based on more frequencies than 
are required under current part 36.
    Section A36.3.7.4 contains a correction to the slow time-weighting 
characteristics in current section A36.3(d)(5) (ii) and (iii). Section

[[Page 45201]]

A36.3.7.6 specifies that the instant in time at which a slow time-
weighted sound pressure level is characterized should be 0.75 seconds 
earlier than the actual readout time. The current requirement specifies 
that the instant in time at which a sound pressure level is 
characterized must be the midpoint of the averaging period.
    Section A36.3.7.5 specifies a continuous exponential averaging 
process equation through which simulated slow time-weighted sound 
pressure levels can be obtained. Section A36.3.7.5 also specifies an 
equation that results in an approximation of continuous exponential 
averaging.
    Section A36.3.7.7 requires that the analyzer resolution be 0.1 dB 
or finer. The current requirement, in section A36.3(d)(7) specifies 
that the amplitude resolution of the analyzer must be at least 
0.25 dB.
    Section A36.3.9.1 requires that calibration adjustments be applied 
to the measured sound levels determined from the output of the 
analyzer; the current rule permits these calibrations to be applied 
within the analyzer. As discussed in the disposition of comments, this 
change is necessary to enable the FAA to determine whether these 
calibration adjustments have been applied correctly.
    Section A36.3.9.3 allows the free-field corrections based on 
grazing incidence to be applied when the sound incidence angle is 
within 30 degrees of grazing incidence.
    Section A36.3.9.4 requires that at lease 30 seconds of pink noise 
be recorded for analog tape recorders; the current section 
A36.3(e)(4)(ii) requirement is for at lease 15 seconds of pink noise. 
This change will result in a more accurate pink noise correction and 
will be the same as the Annex 16 requirement.
    Section A36.3.9.6 requires that attenuator accuracy be within 0.1 
dB. Section A36.3(b)(6) currently requires that attenuator accuracy be 
within 0.2 dB. This final rule requires that calibration be checked 
within six months of each test series, while the current rule does not 
specify a time period.
    Sections A36.3.9.5 and A36.3.9.7 change calibration requirements 
for the pink noise generator and sound calibrator. This change allow 
calibration to occur within six months before or after the test instead 
of requiring it to be within the preceding six months as required by 
current section A36.3(e)(7).
    Section A36.3.9.7 adds a new calibration requirement that limits 
the change in output of the sound calibrator to not more than 0.2 dB.
    Section A36.3.9.8 allows the use of sound calibrators other than 
pistonphones, as specified by current section A36.3(e)(4). Section 
A36.3.8.1 specifies the class 1L requirements of IEC 60942, entitled 
``Electroacoustics--Sound calibrators,'' as the minimum standard for 
the sound calibrator.
    Section A36.3.9.9 adds a requirement for the recording medium 
(e.g., tape reel) to carry at least a 10-second duration sound pressure 
level calibration at its beginning and end. This change more precisely 
defines the current section A36.3(e)(4) sound pressure level 
calibration requirement.

Section A36.4  Calculations of Effective Perceived Noise Level From 
Measured Data

    To further harmonize the formats of part 36 and JAR 36, Table B-1, 
``Perceived Noisiness (NOYs) as a Function of Sound Pressure Level,'' 
referenced in current section B36.13(a), is moved to AC 36-4C. The 
final rule now uses the equation to obtain the values. The noy values 
contained in Table B-1 can be calculated for the equations contain in 
section A36.4.7.3.
    A minor technical change is made to the Perceived Noise Level (PNL) 
equation in section A36.4.2.1(c) (current section B36.3(c)). The more 
exact term 10/log 2 is replacing the rounded-off term 33.22. The 
difference between PNL values that are determined using the current and 
changed equations is not expected to be significant.
    To harmonize the formats of part 36 and JAR 36, Figure B1, 
``Perceived noise level as a function of noys'', is moved from current 
section B36.3(c) to AC36-4C. The perceived noise level values contained 
in figure B1 can be calculated from the equations contained in section 
A36.4.2.1(c).
    Section A36.4.5.2 changes the value of ``d'' in the equation for 
the duration correction factor from 1.0 seconds to 0.5 seconds to 
reflect current standard practice. The same changes are included in 
section A36.4.5.4 and section A36.6. This change is a text update to 
reflect the current practice of using 0.5 second data samples, and has 
no substantive effect.
    To harmonize the formats of part 36 and JAR 36, the material in 
section B36.5(m) addressing methods for removing the effects of tones 
resulting from ground plane reflections is moved to AC 36-4C.
    Current section B36.9(e), which specifies the duration time 
interval when the value of PNLT(k) at the 10 dB-down points is 90 PNdB 
or less, is removed. This provision was eliminated for applications 
made after September 17, 1971, by Amendment 36-5 (41 FR 35053, August 
19, 1976). The text permitting the use of this provision was retained 
in part 36 unnecessarily.
    Section B36.9(f) is also removed. The text contained in current 
section B36.9(f) was added to part 36 in 1976 to distinguish between 
the procedure for determining duration for applications made before and 
after September 17, 1971. This distinction is no longer necessary since 
current section B36.9(e) is removed. The section B36.9(f) requirement 
for the aircraft testing procedures to include the 10 dB-down points is 
contained in section A36.2.3.2 of this final rule.

Section A36.5  Data Reporting

    Section A36.5.2 requires that the data specified in that section be 
reported to the FAA in the applicant's noise certification compliance 
report. While current part 36 does not specifically identify a 
requirement for the applicant to submit a noise certification 
compliance report, these reports represent the standard practice that 
is used by applicants for submitting this information to the FAA. This 
final rule now requires a report be submitted. Section A36.5.2.5 also 
identifies the specific airplane configuration items and engine 
operating parameters that must be reported. Each of these configuration 
items and parameters can affect airplane noise. The reporting 
requirement for these items and parameters exists under current section 
A36.5 which specifies that the aircraft configuration and engine 
performance parameters relative to noise generation be reported. 
Further, these configuration items and parameters are also included in 
the international standard.
    Section A36.5.2.5(c) requires that the test airplane's center of 
gravity be reported to the FAA. Airplane center of gravity is an 
example of an identifying characteristic of the airplane test 
configuration, and is an item that could influence measure noise 
levels. Section A36.5.2.5(d) requires that the airbrake position also 
be reported. Sections A36.5.2.5(e), (f), and (j), respectively, require 
reporting of whether the auxiliary power unit (APU) is operating, the 
status of pneumatic engine bleeds and engine power take-offs, and non-
standard airplane test configurations.
    Section A36.5.2.5(h)(2) requires reporting of engine performance 
parameters specifically related to propeller-driven airplanes.
    Current section A36.5(d)(3) does not permit an effective perceived 
noise level (EPNL) to be computed or reported from data from which more 
than four one-third octave bands in any spectrum

[[Page 45202]]

within the 10 dB-down points have been excluded from the EPNL 
computation. This section is removed since correction (adjustment) 
methods for removing the effects of ambient noise from airplane noise 
data must be used in lieu of excluding one-third octave bands. Section 
A36.3.10.2 will specify the ambient noise level limitations that 
require corrections (adjustments) to be made, and also will reference 
AC 36-4C, which contains a procedure for removing the affects of 
ambient noise.
    Current section A36.5(e)(4), that addresses the use of equivalent 
procedures, is removed. The key requirement of the section, that the 
FAA must approve equivalent procedures, is already addressed in section 
36.101. Additional information on the use of equivalent procedures is 
provided in the note contained in section A36.2.1.1.

Section A36.6  Nomenclature: Symbols and Units

    Section A36.6, Nomenclature: Symbols and units replaces current 
section A36.7, symbols and units. Section A36.6 incorporates ICAO Annex 
16 symbols and units, while retaining the English units. This change is 
made to more closely align part 36 with JAR 36. No substantive 
technical changes are anticipated to result from incorporation of the 
ICAO Annex 16 symbols and units.

Section A36.7  Sound Attenuation in Air

    Currently, atmospheric attenuation rates of sound with distance 
must use be determined in accordance with Society of Automotive 
Engineers, Inc. (SAE), Aerospace Recommended Practice (ARP) 866A (SAE 
ARP 866A), as specified in current section A36.9(c). In this final 
rule, section A36.7.2 contains the actual formulation (equations) from 
SAE ARP 866A. These equations are provided in both the International 
System of Units and the English System of Units. Whereas equations are 
continuous and provide consistent values, tables and graphs can provide 
minor differences. Accordingly, the tables are being removed and 
applicants must use the equation. This change will further harmonize 
part 36 and JAR 36 and is not expected to result in any substantive 
difference in attenuation rates.

Section A36.9  Adjustment of Airplane Flight Test Results

    The current distinction between allowable/required positive and 
negative correction procedures, contained in current sections 
A36.11(a)(1) and (2), is not included in new section A36.9.1. This 
distinction is no longer relevant given: (1) The evolution of data 
correction procedures since part 36 was originally promulgated in 1969 
and, (2) the need for noise certification levels to reflect airplane 
noise characteristics as accurately as possible. Prior to any noise 
certification compliance test, a noise certification applicant is 
required to identify, and obtain FAA approval of, any planned or 
anticipated data correction that is not a mandatory correction 
procedure under part 36.
    Current section A36.1(b)(3) is deleted because it is obsolete. This 
section requires that the corrections prescribed in current section 
A36.5(d) be made when the height of the ground at a noise measuring 
station differs from that of the nearest point on the runway by more 
than 20 feet. A 20-foot height allowance/tolerance could change the 
final EPNL value by several tenths of a dB under some circumstances. 
Under current noise certification practices, corrections (adjustments) 
are made over the sound propagation path from the microphone to 
airplane height as part of normal data corrections (adjustments). These 
corrections (adjustments) are specified in current section A36.11 and 
new section A36.9.
    Section A36.9.1.1(d) will require that the effect that airspeed has 
on source noise be considered with regard to the difference between 
test day airplane speed and the airplane reference flight profile 
speed.
    The symbols and figures used to described the takeoff and approach 
profiles in current sections A36.11(b) and (c), are replaced by the JAR 
36 symbols and figures that have been incorporated into section 
A36.9.2. There are no substantive changes to the takeoff and approach 
profile technical requirements as a result of these changes.
    Section A36.9.3.2.1 provides equations that enable data adjustments 
to be made using either the English System of Units or International 
System of Units.
    The material in current section B36.11(c) will be moved to section 
A36.9.3.2.2 and revised to specify the adjustment for multiple peak 
values of PNLT. This adjustment is based upon the difference in 
corrected PNLT values, rather than upon APNL as in the current part 36. 
This change more clearly defines the intent of the multiple peak 
correction.
    Under section A36.9.3.3.2 a correction term is added to account for 
the difference between (1) the measured airspeed during the noise 
certification flight test and (2) the airspeed calculated for the noise 
certification reference flight procedure. This correction term is added 
to the duration correction ([Delta]2) contained in current section 
A36.11(e). The speed correction term is defined as 10 log (V/
Vr), where V is the airplane test speed and Vr is 
the airplane reference speed. This change specifies the speed 
correction that is required by current section A36.11(f)(1).

Appendix B--Noise Levels for Transport Category and Jet Airplanes Under 
Sec. 36.103

    Appendix B will include the material from current appendix C. This 
will make Appendix B essentially the same as JAR 36, section 1, subpart 
B.

Section B36.3  Reference Noise Measurement Points

    The material in current section C36.3 is moved to section B36.3 and 
revised as follows. The term ``takeoff'' in current section C36.3(a) is 
replaced with the term ``flyover'' in section B36.3(b). The term 
``sideline'' in current section C36.3(c) is replaced with ``lateral'' 
in section B36.3(a). These terminology changes harmonize the part 36 
terminology with that used in JAR 36 and ICAO Annex 16.
    Section B36.3(a)(2) will include a simplified test procedure that 
may be used in determining the sideline (lateral) noise certification 
level for propeller-driven airplanes. This procedure is also contained 
in JAR 36 and ICAO Annex 16. For propeller-driven airplanes, it can be 
difficult to establish the maximum lateral noise level specified under 
current section C36.3(c) because this noise level may occur at a very 
low height. There is usually a significant difference in noise levels 
between the port and starboard sides of a propeller-driven airplane. By 
measuring full-power noise at a predetermined point (650 meters) below 
the takeoff flight path, many of the difficulties that arise because of 
the directional nature of the noise from propeller-driven airplanes 
when measured at the conventional lateral site will be eliminated. 
Ground effects that distort measurements will also be reduced.
    Under the current requirement, it is difficult to judge the 
airplane altitude at which the peak noise level occurs, and in the past 
this has required applicants to conduct as many as 30 flight tests to 
satisfy certifying authorities, an expensive process. Moreover, the 
current method for testing propeller-driven airplanes has generally 
resulted in low confidence in accuracy and repeatability of 
measurements. The

[[Page 45203]]

simplified test procedure is available as an alternative to the current 
section C36.3(c) method for tests conducted before August 7, 2002, 
after which it will become the sole method for demonstrating sideline 
(lateral) noise level compliance.
    Current section C36.3(b) is moved to section B36.3(c) and text is 
added to define the approach measurement point relative to the runway 
threshold. This change will clearly describe the geometric relationship 
between the test airplane and the ground, and will harmonize part 36 
and JAR 36.
    Current section A36.1(b)(7), allows (when approved) for the 
sideline (lateral) noise certification level demonstration for jet 
airplanes to be based on the assumption that the peak sideline 
(lateral) noise level occurs at an airplane altitude of 1,000 feet 
(1,440 feet for Stage 1 or Stage 2 four-engine airplanes). Notice No. 
00-08 proposed to move this procedure to the guidance material in AC 
36-4C. Subsequent to the publication of Notice No. 00-08, however, the 
FAA determined that it is more appropriate to retain this procedure in 
part 36 as an alternative procedure for determining the maximum lateral 
noise level. This procedure is included in section B36.3(a)(1). In 
addition, the target altitude and target altitude tolerance 
requirements of this section are adjusted so that they are now 
consistent with those of the similar procedure contained in section 
2.1.3.2 of the ICAO Environment Technical Manual.

Section B36.4  Test Noise Measurement Points

    Most of the requirements of current section A36.1(b)(7) are moved 
to section B36.4.
    Section B36.4(b) requires that, in demonstrating the sidelines 
(lateral) noise certification level for propeller-driven airplanes, 
noise measurements be made at symmetrically located noise measurements 
points on either side of the runway for each and every noise 
measurement point along the main sideline (lateral) noise measurement 
line. This change is made because of the asymmetric nature of propeller 
noise. Part 36 has required simultaneous measurement at one test 
measurement point opposite the main lateral measurement line to account 
for the possibility of lateral noise asymmetry. In the case of 
propeller-driven airplanes, however, whose noise field is known to be 
asymmetrical, having only one measuring point opposite the main lateral 
measurement line is not adequate to define the peak lateral noise on 
the other side of runway from the main lateral line. This change will 
further harmonize part 36 and JAR 36.

Section B36.5  Maximum Noise Levels

    The material in current section C36.5 is moved to section B36.5 and 
revised to include minor format and language changes to harmonize with 
JAR 36. Amendment 36-15 ``Standards Governing the Noise Certification 
of Aircraft'' (53 FR 26360, May 6, 1988) removed section C36.5(c); the 
references to section C36.5(c) in current section C36.5(a) should have 
been removed under that amendment but was not. The reference is removed 
in this final rule.
    In order to further harmonize part 36 and JAR 36, the term 
``sideline'' has been changed to ``lateral'' in each place that it 
appears throughout section B36.5. This change in terminology does not 
affect the noise measurement/analysis procedures or noise limits. 
Similarly, the term ``takeoff'' has been changed to ``flyover.'' No 
change in test procedures should be inferred from this change.

Section B36.6  Trade-offs

    The requirements of current section C36.5(b) are moved to section 
B36.6. The reference to section 367(d)(3)(i)(B), in current section 
C36.5(b), is changed to section 36.7(d)(1)(ii) in the new section. This 
section reference should have been changed in 1988 by Amendment 36-15.

Section B36.7  Noise Certification Reference Procedures

    The takeoff and approach reference and test limitation in current 
sections C36.7 and C36.9 are moved to sections B36.7 and B36.8. This 
material is also revised as follows.
    Section B36.7(b)(1) requires the use of ``average engine'' 
performance in defining the takeoff thrust for the reference takeoff 
procedure. Specifying the use of ``average engine'' performance further 
harmonizes the part 36 takeoff reference procedure with JAR and ICAO 
Annex 16, and will eliminate confusion in compliance with the 
requirement.
    Section B36.7(b)(1) also specifies ``Takeoff thrust/power'' as the 
maximum available for normal operations given in the performance 
section of the airplane flight manual for the reference atmospheric 
conditions given in section B36.7(a)(5).
    Currently section C36.7(b)(2) specifies different minimum cutback 
altitudes for jet and propeller-driven airplanes. Section 
B36.7(b)(1)(ii) contains the same minimum cutback altitude for all 
airplanes, which is the altitude specified in current section 
C36.7(b)(2) for jet airplanes. Since the selection of the minimum 
cutback altitude is determined by the minimum safe altitude for cutback 
initiation, there is no reason to distinguish between propeller-driven 
and jet airplanes. It is the FAA's understanding that this change will 
not have a substantive effect in practice.
    Since cutback initiation heights greater than 1,500 feet are 
generally chosen for propeller-driven airplanes and this height is 
greater than both the current and revised part 36 minimum requirements, 
the FAA has determined that there will be no change in practice.
    In this final rule, the requirements of section A36.1(b)(2) are 
moved to section B36.7(b)(3) and revised to require that, for tests 
conducted on or after August 7, 2002, the lateral (sideline) noise 
level be demonstrated using full takeoff power throughout the takeoff 
flight path. Before that date, the lateral noise level may be 
demonstrated using the current section A36.1(b)(2) procedure, under 
which both the takeoff (flyover) and sideline (lateral) noise 
certification levels are determined using a single reference flight 
path that may include a thrust cutback. This change reflects the intent 
of the international standard that the lateral measurement be based on 
the full-power condition. Since the revised lateral procedure might 
result in increased stringency, the use of this procedure is optional 
for tests conducted before August 7, 2002. This change will mainly 
affect three and four engine airplanes.
    The takeoff reference speed requirement specified in current 
section C36.7(e)(1) is revised to be consistent with the takeoff 
reference speed contained in JAR 36 and ICAO Annex 16. The all-engine 
operating climb speed range (V2+10 to V2+20 kts) specified in section 
B36.7(b)(4) represents the typical range of takeoff initial climb speed 
seen in normal operation for most airplanes. For some airplanes, this 
change to part 36 could result in an increase of up to 10 knots in the 
noise certification reference takeoff speed relative to the current 
part 36 reference takeoff speed requirements. For the affected 
airplanes, the increased takeoff speed could result in some noise level 
reduction at the sideline (lateral) noise measurement point with a 
resulting increase in noise level at the takeoff (flyover) noise 
measurement point. The FAA has found the change in takeoff reference 
speed to be acceptable because of this tradeoff of sideline (lateral) 
and takeoff (flyover) noise levels, although it might not be a one-to-
one tradeoff.
    In section B36.7(b)(5) the FA is adding a definition of 
configuration, which includes specific configuration

[[Page 45204]]

elements, based on certification experience, that can have a effect on 
source noise. There is no change in takeoff configuration requirement.
    Section B36.7(b)(7) defines ``average engine'' as the average of 
all the certification compliant engines used during the airplane flight 
tests up to and during certification when operating within the 
limitations and according to the procedures given in the Flight Manual.
    Current section C36.9(d) requires that all engines must operate at 
approximately the same power or thrust for approach tests conducted to 
demonstrate compliance with part 36. In this final rule, this specific 
requirement is removed, and instead, section A36.9.3.4 will require 
that source noise adjustments be applied to account for any differences 
between test and reference conditions, in engine parameters that affect 
engine noise (e.g., corrected low pressure rotor speed). This change 
will meet the intent of the current part 36 requirement and also 
further harmonizes with JAR 36.
    Current section C36.9(e)(1), reference approach speed, is revised 
to incorporate the use of 1-g stall-based approach speeds by basing the 
approach noise certification reference speed on the reference landing 
speed (VREF) that is used for the airworthiness 
certification. In Notice No. 95-17, published on January 18, 1996 (61 
FR 1260), the FAA proposed to redefine the reference stall speeds for 
transport category airplanes as the 1-g stall speed instead of the 
minimum speed obtained in the stalling maneuver. Notice No. 95-17 
proposed that a definition of VREF would be added to 14 CFR 
part 1. Since a final rule based on Notice No. 95-17 has not been 
published, the definition of VREF has been included in this 
final rule. The definition of VREF is the only element of 
Notice No. 95-17 that has been included in this final rule. In section 
B36.7(c)(2), VREF is defined as ``the speed of the airplane, 
in a specified landing configuration, at the point where it descends 
through the landing screen height in the determination of the landing 
distance for manual landings.'' The change to section C36.9(e)(1) is 
also consistent with a change to ICAO Annex 16 that was approved by the 
ICAO Council on June 27, 2001. Current section C36.9(e)(1) is 
redesignated as section B36.7(c)(2).

Section B36.8  Noise Certification Test Procedures

    Current sections A36.1(d)(5) and A36.1(d)(7), which contain 
limitations on the difference between the test weight and the maximum 
takeoff/approach weight for which noise certification is requested, are 
replaced by section B36.8(d). The current limitations help insure the 
integrity of the final certification results by indirectly limiting the 
magnitude of the EPNL adjustments that may be applied to the test data 
in normalizing to the noise certification reference conditions. Section 
B36.8(d) will directly limit the magnitude of the correction by 
specifying a limitation on the EPNL adjustment that can be made when 
correcting between test weight and maximum certification weight.
    The current requirements of section A36.5(d)(5) are revised and 
moved to section B36.8(f). The amounts of adjustment permitted when 
equivalent test procedures are different from the reference procedures 
remain unchanged, except that the amended requirements do not specify 
that tradeoffs are permitted when comparing adjusted levels against the 
appendix B noise level limits, for the purpose of determined adjustment 
limits. Several interpretations of the current requirement are possible 
as to whether this final rule represents a more stringent or less 
stringent adjustment limitation as compared with the current 
limitation. The FAA believes that the change to remove the tradeoff 
provision from the current limitation and base the limitation solely on 
the difference between the adjusted noise levels and the maximum noise 
levels in section B36.5 meets the intent of the adjustment limitation, 
as stated above, and clarifies ambiguity in its interpretation. The 
change also results in harmonization of the adjustment limitation with 
that in JAR 36 and ICAO Annex 16.
    Section B36.8(g) will revise the test speed tolerance specified in 
current sections C36.7(e)(1) and C36.9 (e)(3). Current section 
C36.7(e)(1) specifies that takeoff tests must be conducted at the test 
day speeds 3 knots. Current section C36.9(e)(3) specifies 
that a tolerance of 3 knots may be used throughout the 
approach noise testing. Section B36.8(g) will specify that during 
takeoff, lateral, and approach tests, the airplane variation in 
instantaneous indicated airspeed must be maintained within 
3% of the average airspeed between the 10 dB-down points. 
In the final rule, the instantaneous indicated airspeed is determined 
from the pilot's airspeed indicator. If the instantaneous indicated 
airspeed exceeds 3 kt (5.5 km/h) of the average 
airspeed over the 10 dB-down points, and is determined by the FAA 
representative on the flight deck as the result of atmospheric 
turbulence, then that flight must be rejected for noise certification 
purposes.

Appendix G--Noise Requirements for Propeller-Driven Small Airplanes and 
Commuter Category Airplanes Under Subpart F

Section G36.105  Sensing, Recording, and Reproducing Equipment

    To maintain the correct cross reference, this final rule changes 
the references in paragraph (f) from section A36.3(e) to A36.3.8 and 
A36.3.9.

Appendix H--Noise Requirements for Helicopters Under Subpart H Section 
H36.101 Noise Certification Test and Measurement Conditions.

    To maintain the correct cross reference, this final rule amends 
section H36.101(d)(1) by removing the reference to ``appendix B'' and 
adding ``appendix A.''

Section H36.111  Reporting and Correcting Measured Data

    To maintain the correct cross reference, this final rule amends 
section H36.111(c)(3) by removing the reference ``A36.3(f)(3)'' and 
adding ``A36.3.10.1.''

Section H36.201  Noise Evaluation in EPNdB

    To maintain the correct cross reference, this final rule amends 
section H36.201 by: (1) Removing the reference to ``appendix B'' in 
paragraph (a) of this section and adding ``appendix A,'' and (2) 
removing the reference to ``B36.5(a)'' in paragraph (b) of this section 
and adding ``A36.4.3.1(a).''

Sections 91.801 and 91.851

    Section 901.801(a)(1), 91.801(a)(2), 91.801(c), 91.801(d), and 
91.851, which are related to the part 36 noise certification 
requirements, are revised to incorporate the term ``jet'' in addition 
to ``turbojet'' when referring to turbojet or turbofan engines. This 
change is made to reflect the use of the term ``jet'' in part 36 and 
does not change the meaning of the term turbojet as it is used in 
either the noise certification related sections, or other sections of 
14 CFR chapter 1.

               Redesignation Table for Appendices A and B
------------------------------------------------------------------------
                          Cross Reference Table
-------------------------------------------------------------------------
           Old section                          New section
------------------------------------------------------------------------
A36.1                             A36.1, A36.2
A36.1(a)                          A36.1.1, A36.2.1.1
A36.1(b)                          A36.2.2
A36.1(b)(1)                       A36.2.3.2, B36.3
A36.1(b)(2)                       A36.7(b)(3)
A36.1(b)(3)                       Deleted
A36.1(b)(4)                       A36.2.2.1
A36.1(b)(5)                       A36.2.2.4
A36.1(b)(6)                       A36.2.2.1

[[Page 45205]]

 
A36.1(b)(7)                       A36.9.3.5, A36.9.3.5.1, B36.4(b)
A36.1(c)                          A36.2.2.2
A36.1(c)(1)                       A36.2.2.2(a)
A36.1(c)(2)                       A36.2.2.2(b)
A36.1(c)(3)                       A36.2.2.2(c)
                                  AC 36-4C
A36.1(c)(4)                       A36.2.2.2(e)
A36.1(c)(5)                       A36.2.2.2(f)
A36.1(d)(1)                       B36.8(b), B36.2
A36.1(d)(2)                       A36.2.3.1
A36.1(d)(3)                       A36.2.3.2, A36.2.3.3
A36.1(d)(4)                       B36.7(b), B36.8
A36.1(d)(5)                       B36.8(d)
A36.1(d)(6)                       B36.7(c), B36.8(e)
A36.1(d)(7)                       B36.8.(d)
A36.1(d)(8)                       A36.2.3.3
A36.3                             A36.3
A36.3(a)                          A36.3.3
A36.3(b)                          A36.3.3.1
A36.3(c)(2)(i-iv), A36.3(f)(1)    A36.3.5
A36.3(c)(2)(v)                    A36.3.4
A36.3(c)(3)                       A36.3.6
A36.3(d)                          A36.3.7
A36.3(e)(1-6), A36.3(f)(2)        A36.3.9
A36.3(f)(2-4)                     A36.3.10.1
A36.3(e)(7)                       A36.3.8
A36.5(a)                          A36.5.1.1, A36.5.1.2, A36.5.1.3
A36.5(b)(1)                       A36.5.2.1
A36.5(b)(2)                       A36.5.2.2
A36.5(b)(3)                       A36.5.2.3
A36.5(b)(4)                       A36.5.2.4
A36.5(b)(5)(i-vi)                 A36.5.2.5
A36.5(b)(vii)                     A36.5.2.5(i)
A36.5(b)(6)                       A36.2.3.2, A36.2.3.3
                                  A36.5.2.5(i)
A36.5(c)                          A36.5.3
A36.5(c)(1)                       B36.7(a)(5)
A36.5(c)(2)                       B36.3(c), B36.7(b)(6), B36.7(c)(1),
                                   B36.7(c)(4)
A36.5(d)(1)                       A36.5.3.1, A36.9, B36.8(c)
A36.5(d)(2)                       A36.9.1
A36.5(d)(2)(i)-(iv)               B36.8(d)
A36.5(d)(3)                       A36.3.10.2
A36.5(d)(4)                       A36.3.10.2
A36.5(d)(5)                       B36.8(f)
A36.5(e)(1)                       A36.5.4.1
A36.5(e)(2)                       A36.5.4.2
A36.5(e)(3)                       A36.5.4.3
A36.5(e)(4)                       Deleted
A36.7                             A36.6, A36.9.5, A36.9.6
A36.9(a)                          A36.9.1.1
A36.9(b)(1)                       A36.2.2.4
A36.9(b)(2)                       A36.2.2.2(b)
A36.9(b)(3)                       A36.2.2.2(g)
A36.9(c)                          A36.7
A36.9(d)(1)                       A36.9.1, A36.9.1.1
A36.9(d)(2)                       A36.2.2.2(d)
A36.9(d)(3)                       A36.2.2.3
A36.11(a)                         A36.9.1
A36.11(a)(1)                      Deleted
A36.11(a)(2)                      Deleted
A36.11(a)(3)(i)                   A36.9.1, B36.7
A36.11(a)(3)(ii)                  A36.9.1.1
A36.11(a)(3)(iii)                 A36.9.1.1
A36.11(a)(3)(iv)                  A36.9.1.1, A36.9.3.4
A36.11(a)(3)(v)                   A36.9.1
A36.11(b)(1)(i-ii)                A36.9.2.1
A36.11(b)(2)                      A36.9.3.1, A36.9.4.1
A36.11(b)(3)                      A36.9.3.2(a)
A36.11(c)                         A36.9.2.2
A36.11(c)(1)                      A36.9.3.2(a-c)
A36.11(c)(2)                      A36.9.3.2(a)
A36.11(d)(1-3)                    A36.9.3, A36.9.3.1, A36.9.3.2.1,
                                   A36.9.3.2.1.1, A36.9.3.2.1.2
A36.11(e)(1-2)                    A36.9.3.3.1, A36.9.3.3.2
A36.11(f)                         B36.4(a), AC 36-4C
A36.11(f)(1)                      A36.9.1.2
A36.11(f)(2)                      A36.9.1.2
A36.11(f)(2)(i-ii)                A36.9.4
B36.1                             A36.1, A36.1.1, A36.4.1.3
B36.1(a)                          B36.4.1.3(a)
B36.1(b)                          A36.4.1.3(b)
B36.1(c)                          A36.4.1.3(c)
B36.1(d)                          A36.4.1.3(d)
B36.1(e)                          A36.4.1.3(e)
B36.3                             A36.4.2.1
B36.3(a)                          A36.4.2.1(a)
B36.3(b)                          A36.4.2.1(b)
B36.3(c)                          A36.4.2.1(c), AC 36-4B
B36.5                             A36.4.3.1
B36.5(a)                          A36.4.3.1(a)
B36.5(b)                          A36.4.3.1(b)
B36.5(c)                          A36.4.3.1(c)
B36.5(d)                          A36.4.3.1(d)
B36.5(e)                          A36.4.3.1(e)
B36.5(f)                          A36.4.3.1(f)
B36.5(g)                          A36.4.3.1(g)
B36.5(h)                          A36.4.3.1(h)
B36.5(i)                          A36.4.3.1(i)
B36.5(j)                          A36.4.3.1(j)
B36.5(k)                          A36.4.3.1(j)
B36.5(l)                          A36.4.3.1(j)
B36.5(m)                          A36.4.3.1(j), AC 36-4C
B36.5(n)                          A36.4.4.2
B36.7                             A36.4.4
B36.7(a)                          A36.4.4.1, A36.4.4.1 Note 1
B36.7(b)                          A36.4.4.1-Note 2
B36.9                             A36.4.5.1
B36.9(a)                          A36.4.5.2
B36.9(b)                          A36.4.5.3
B36.9(c)                          A36.4.5.4
B36.9(d)                          A36.4.5.5
B36.9(e)                          Deleted
B36.9(f)                          Deleted
B36.11(a)                         A36.4.6
B36.11(b)                         Deleted
B36.11(c)                         A36.9.3.2.2
B36.13(a)                         A36.4.7.1, Table A1 moved to AC 36-4C
B36.13(a)(1), (2), (3)            A36.4.7.2(a-c)
B36.13(b)                         A36.4.7.3
B36.13(c)                         A36.4.7.4
C36.1                             B36.1
C36.3(a)                          B36.3(b)
C36.3(b)                          B36.3.(c)
C36.3(c)                          B36.3(a)
C36.5(a)                          B36.5
C36.5(a)(1)                       B36.5(a)
C36.5(a)(2)                       B36.5(b)
C36.5(a)(2)(i)                    B36.5(b)(1)
C36.5(a)(2)(ii)                   B36.5(b)(2)
C36.5(a)(3)                       B36.5(c)
C36.5(a)(3)(i)(A)                 B36.5(c)(1)(i)
C36.5(a)(3)(i)(B)                 B36.5(c)(1)(ii)
C36.5(a)(3)(i)(C)                 B36.5(c)(1)(iii)
C36.5(a)(3)(ii)                   B36.5(c)(2)
C36.5(a)(3)(iii)                  B36.5(c)(3)
C36.5(b)(1)                       B36.6
C36.5(b)(2)                       B36.6
C36.5(b)(3)                       B36.6
C36.7(a)                          B36.7(a)(3)
C36.7(b)                          B36.7(b)(1)(i)
C36.7(b)(1)                       B36.7(b)(1)(i)
C36.7(b)(2)                       B36.7(b)(1)(ii)
C36.7(c)                          B36.7(b)(2)
C36.7(d)                          B36.7(b)(5)
C36.7(e)(1)                       B36.7(b)(4)
C36.7(e)(1) Next to last          B36.8(g)
 sentence
C36.7(e)(2)                       B36.7(b)(4)
C36.7(e)(3)                       B36.7(a)(5), A36.9.1
C36.9.(a)                         B36.7(a)(3), B36.7(c)(1)
C36.9(b)                          B36.7(c)(3) & B36.7(c)(4)
C36.9(c)                          B36.7(c)(1), B36.7(c)(3)
C36.9(d)                          Deleted
C36.9(e)(1)                       B36.7(c)(2)
C36.9(e)(2)                       B36.7(c)(2)
C36.9(e)(3)                       B36.8(g)
------------------------------------------------------------------------


                          Cross Reference Table
------------------------------------------------------------------------
                New section                          Old section
------------------------------------------------------------------------
A36.1.....................................  A36.1, B36.1
A36.1.1...................................  A36.1(a), B36.1
A36.1.2...................................  New section
A36.1.3...................................  New section
A36.2.....................................  A36.1
A36.2.1...................................  A36.1(a)
A36.2.1.1.................................  A36.1(a)
A36.2.2...................................  A36.1(b)
A36.2.2.1.................................  A36.1(b)(4), A36.1(b)(6)
A36.2.2.2.................................  A36.1(c)
A36.2.2.2(a)..............................  A36.1(c)(1)
A36.2.2.2(b)..............................  A36.1(c)(2), A36.9(b)(2)
B36.2.2.2(c)..............................  A36.1(c)(3)
B36.2.2.2(d)..............................  A36.9(d)(2)
A36.2.2.2(e)..............................  A36.1(c)(4)
A36.2.2.2(f)..............................  A36.1(c)(5)
A36.2.2.2(g)..............................  A36.9(b)(3)
A36.2.2.3.................................  A36.9(d)(3)
A36.2.2.4.................................  A36.1(b)(5), A36.1(d)
A36.2.3...................................  A36.1(d)
A36.2.3.1.................................  A36.1(d)(2)

[[Page 45206]]

 
A36.2.3.2.................................  A36.1(b)(1), A36.1(d)(3),
                                             A36.5(b)(6)
A36.2.3.3.................................  A36.1(d)(8), A36.5(b)(6)
A36.3.....................................  A36.3
A36.3.1...................................  New
A36.3.2...................................  New
A36.3.3...................................  A36.3(a)
A36.3.3.1.................................  A36.3(b)
A36.3.3.2.................................  New
A36.3.4...................................  A36.3(c)(2)(v)
A36.3.5...................................  A36.3(c)(2)(i-iv),
                                             A36.3(f)(1)
A36.3.6...................................  A36.3(c)(3)
A36.3.7...................................  A36.3(d)
A36.3.8...................................  A36.3.(e)(7)
A36.3.9...................................  A36.3(e)(1-6), A36.3(f)(2)
A36.3.10.1................................  A36.3(f)(2-4)
A36.3.10.2................................  A36.5(d)(3-4)
A36.4.....................................  B36.1
A36.4.1...................................  B36.1
A36.4.1.1.................................  B36.1
A36.4.1.2.................................  B36.1
A36.4.1.3.................................  B36.1
A36.4.2...................................  B36.3
A36.4.2.1.................................  B36.3; AC 36-4C
A36.4.3...................................  B36.5
A36.4.3.1.................................  B36.5(a-m)
A36.4.3.2.................................  B36.5(n)
A36.4.4...................................  B36.7
A36.4.4.1.................................  B36.7 (a) & (b)
A36.4.4.2.................................  B36.5(n)
A36.4.5...................................  B36.9
A36.4.5.1.................................  B36.9
A36.4.5.2.................................  B36.9(a)
A36.4.5.3.................................  B36.9(b)
A36.4.5.4.................................  B36.9(c)
A36.4.5.5.................................  B36.9(d)
A36.4.6...................................  B36.11
A36.4.6...................................  B36.11(a)
A36.4.7...................................  B36.13
A36.4.7.1.................................  B36.13(a)
A36.4.7.2.................................  B36.13(a) (1-3)
A36.4.7.3.................................  B36.13(b)
A36.4.7.4.................................  B36.13(c)
A36.5.....................................  A36.5
A36.5.1...................................  A36.5(a)
A36.5.1.1.................................  A36.5(a)
A36.5.1.2.................................  A36.5(a)
A36.5.1.3.................................  A36.5(a)
A36.5.2...................................  A36.5(b)
A36.5.2.1.................................  A36.5(b)(1)
A36.5.2.2.................................  A36.5(b)(2)
A36.5.2.3.................................  A36.5(b)(3)
A36.5.2.4.................................  A36.5(b)(4)
A36.5.2.5.................................  A36.5(b)(5)
A36.5.3...................................  A36.5(c)
A36.5.3.1.................................  A36.5(d)(1)
A36.5.4...................................  A36.5(e)
A36.5.4.1.................................  A36.5(e)(1)
A36.5.4.2.................................  A36.5(e)(2)
A36.5.4.3.................................  A36.5(e)(3)
A36.6.....................................  A36.7
A36.7.1-A36.7.3...........................  A36.9(c)
A36.8.....................................  New section--Reserved
A36.9.....................................  A36.5(d)(1), A36.11
A36.9.1...................................  A36.5(d)(2), A36.9(d)(1),
                                             A36.11(a), A36.11(a)(3)(i)
                                             & (v)
A36.9.1.1.................................  A36.9(a), A36.9(d)(1),
                                             A36.11(a)(3)(ii-iii),
                                             A36.11(a)(3)(iv)
A36.9.1.2.................................  A36.11(f) (1-2)
A36.9.2...................................  A36.11(b) & (c)
A36.9.2.1.................................  A36.11(b)(1)(i-ii)
A36.9.2.2.................................  A36.11(c)
A36.9.3...................................  A36.11
A36.9.3.1.................................  A36.11(a), A36.11(f)(1)
A36.9.3.2(a)..............................  A36.11(b)(3), A36.11(c)(2)
A36.9.3.2.(b).............................  New section
A36.9.3.2.1...............................  A36.11(d)(1-3)
A36.9.3.2.1.1.............................  A36.11(d)(1)(ii)
A36.9.3.2.1.2.............................  A36.11(d)(1)(ii)
A36.9.3.2.2...............................  A36.11(c)
A36.9.3.3.................................  A36.11(e)
A36.9.3.3.1...............................  A36.11(e)(1)-(2)
A36.9.3.3.2...............................  A36.11(e)
A36.9.3.4.................................  A36.11(a)(3)(iv)
A36.9.3.4.1...............................  A36.11(a)(3)(iv)
A36.9.3.4.2...............................  A36.11(a)(3)(iv)
A36.9.3.5.................................  A36.1(b)(7)
A36.9.3.5.1...............................  A36.1(b)(7)
A36.9.4...................................  A36.11(f)(2) (i-ii)
A36.9.4.1.................................  A36.11(b)(2), A36.11(f)(2)(i-
                                             ii)
A36.9.4.2.................................  A36.11(f)(2)(i-ii)
A36.9.4.2.2...............................  A36.11(f)(2)(i-ii)
A36.9.4.2.3...............................  A36.11(f)(2)(i-ii)
A36.9.4.3.................................  A36.11(f)(2)(i-ii)
A36.9.4.4.................................  A36.11(f)(2)(i-ii)
A36.9.4.4.1...............................  A36.11(f)(2)(i-ii)
A36.9.5...................................  A36.7
A36.9.6...................................  A36.7
B36.1.....................................  C36.1
B36.2.....................................  A36.1(d)(1)
B36.3(a)..................................  C36.3(c)
B36.3(b)..................................  C36.3(a)
B36.3(c)..................................  A36.5(c)(2), C36.3(b)
B36.4(a)..................................  A36.11(f)
B36.4(b)..................................  A36.1(b)(7)
B36.5.....................................  C36.5(a)
B36.5(a)..................................  C36.5(a)(1)
B36.5(b)..................................  C36.5(a)(2)
B36.5(b)(1)...............................  C36.5(a)(2)(i)
B36.5(b)(2)...............................  C36.5(a)(2)(ii)
B36.5(c)..................................  C36.5(a)(3)
B36.5(c)(1)(i)............................  C36.5(a)(3)(i)(A)
B36.5(c)(1)(ii)...........................  C36.5(a)(3)(i)(B)
B36.5(c)(1)(iii)..........................  C36.5(a)(3)(i)(C)
B36.5(c)(2)...............................  C36.5(a)(3)(ii)
B36.5(c)(3)...............................  C36.5(a)(3)(iii)
B36.6.....................................  C36.5(b)(1)-(3)
B36.7(a)(1)...............................
B36.7(a)(2)...............................  A36.11(a)(3)(i)
B36.7(a)(3)...............................  C36.7(a), C36.9(a)
B36.7(a)(4)...............................  New section--Reserved
B36.7(a)(5)...............................  A36.5(c)(1), C36.7(e)(3)
B36.7(b)(1)...............................  C36.7(b)
B36.7(b)(2)...............................  C36.7(c)
B36.7(b)(3)...............................  A36.1(b)(2)
B36.7(b)(4)...............................  C36.7(e)(1-2)
B36.7(b)(5)...............................  C36.7(d)
B36.7(b)(6)...............................  A36.5(c)(2)
B36.7(b)(7)...............................  New section
B36.7(c)..................................  C36.9
B36.7(c)..................................  C36.9(a)
B36.7(c)(1)...............................  C36.5(c)(2), C36.9(c)
B36.7(c)(2)...............................  C36.9(e)(1), C36.9(e)(2)
B36.7(c)(3)...............................  C36.9(b-c)
B36.7(c)(4)...............................  C36.5(c)(2)
B36.7(c)(5)...............................  C36.9(b)
B36.8(a)..................................  New section
B36.8(b)..................................  A36.1(d)(1)
B36.8(c)..................................  A36.5(d), A36.11(a)
B36.8(d)..................................  A36.1(d)(2)(i-iv)
B36.8(e)..................................  A36.1(d)(6)
B36.8(f)..................................  A36.5(d)(5)
B36.8(g)..................................  C36.7(e)(1), C36.9(e)(3)
------------------------------------------------------------------------

Paperwork Reduction Act

    Notice No. 00-08, Noise Certification Standards for Subsonic Jet 
Airplanes and Subsonic Transport Category Large Airplanes, contained 
proposed information collection requirements. As required by the 
Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)), the FAA submitted 
a copy of the proposed rule to the Office of Management and Budget 
(OMB) for its review.
    The agency did not receive any comments concerning this collection 
of information. The collection of information was approved and assigned 
OMB Control Number 2120-0659.

Compatibility With ICAO Standards

    In keeping with the U.S. obligations under the Convention on 
International Civil Aviation, it is FAA policy to comply with 
International Civil Aviation Organization (ICAO) Standards and 
Recommended Practices to the maximum extent practicable. The FAA has 
reviewed the corresponding ICAO Standards and Recommended Practices and 
has identified the following differences with these proposed 
regulations. The FAA is participating in an effort, sponsored by the 
ICAO Committee on Aviation Environmental Protection (CAEP) Working 
Group 1, that is aimed at resolving these differences. Any remaining 
differences with Annex 16 Recommended Standards and Practices after 
conclusion of these efforts will be filed with ICAO. Differences will 
not be filed for those items that are ``notes'' in Annex 16.
    Wind Speed. Section A36.2.2.2(e) of this final rule requires that 
tests be carried out under atmospheric conditions where the average 
wind velocity 10 meters above ground does

[[Page 45207]]

not exceed 12 knots and the crosswind velocity for the airplane does 
not exceed 7 knots. Section A36.2.2.2(e) of the final rule also 
specifies that maximum wind velocity 10 meters above ground is not to 
exceed 15 knots and the crosswind velocity is not to exceed 10 knots 
during the 10 dB-down time interval. Section A36.2.2.2(e) of ICAO Annex 
16, Appendix 2 contains a similar average wind speed limitation, but 
specifies a maximum windspeed limitation only in cases where an 
anemometer with a built-in detector time constant of less than 30 
seconds is used. The FAA has not agreed to adopt this ICAO Annex 16 
provision because it could result in tests being conducted in windspeed 
conditions that exceed those currently permitted under part 36; based 
on the information that was available to it, the harmonization working 
group could not determine the effect that these higher wind conditions 
might have on the resulting noise levels.
    Adjustments to PNL and PNLT. In adjusting measured sound pressure 
level data to reference conditions, a note in Annex 16, Appendix 2 
section 9.3.2.1 suggests that when a sound pressure level value is 
equal to zero (for example, as a result of applying a background noise 
correction) the adjusted sound pressure level must be kept equal to 
zero in the adjustment process. The FAA does not agree with this 
provision. The FAA has determined that the sound pressure level values 
should be carried through the adjustment process regardless of whether 
they are greater than zero, equal to zero, or less than zero. It is 
entirely possible for a negative or zero sound pressure level value 
that results from the background noise correction process to become 
positive when adjusted to account for the difference between the test 
and reference airplane heights above the noise measurement point.
    Design characteristics that requires different reference 
procedures. Section 3.6.1.4 of ICAO Annex 16, Chapter 3 permits the 
certificating authority to approve reference procedures that are 
different from those contained in sections 3.6.2 and 3.6.3 of ICAO 
Annex 16 when design characteristics of an airplane would prevent 
flight from being conducted in accordance with sections 3.6.2 and 3.6.3 
of ICAO Annex 16. The FAA will not adopt this ICAO Annex 16 provision. 
The FAA recognizes that there may be a need for changes to the 
specified reference procedures when part 36 may not be appropriate for 
a particular airplane. In cases where part 36 is not appropriate, the 
rulemaking process, which includes a public comment period, would be 
followed to develop an appropriate noise certification standard. 
Accordingly, although the provision is not being adopted, the section 
reference will be reserved to preserved the ICAO format as much as 
possible.
    Noise Certificates. A note in section 1.2 of ICAO Annex 16, Chapter 
1 indicates that documents attesting to noise certification may take 
the form of a separate noise certificate or a suitable statement 
contained in another document approved by the State of Registry and 
required by that State to be carried in the aircraft. The FAA however, 
is not authorized to issue noise certificates.
    The U.S. regulations require that the certification noise levels be 
included in the Airplane Flight Manual (AFM)/Rotorcraft Flight Manual 
(RFM), and an AFM/REM is approved for each carrier/operator or 
airplane/rotorcraft model by the FAA. Some U.S. operating regulations, 
however, such as 14 CFR part 121, allow an operator to create an 
operations manual that is based on the limitations and performance 
requirements contained within the FAA-approved AFM. This manual is 
required to be used by the flight, maintenance, and ground crews of the 
operators. There is no specific requirement that the entire FAA-
approved AFM be carried in the airplane. The operations manual (or 
Flight Crew Operating Manual) may not contain the noise characteristics 
page from the FAA-approved AFM depending on how the manual was 
constructed and whether or not the information contained on the noise 
characteristics page was deemed of any benefit to the flight or 
operations crews.
    In Notice No. 00-08, the FAA invited comments on the extent of any 
problems encountered due to the absence of noise compliance 
substantiation when the Airplane Flight Manual is not on board the 
airplane. One comment was received on this subject and is included 
under the Discussion of Comments section of this preamble.

Economic Summary

    Proposed changes to Federal regulations must undergo several 
economic analyses. First, Executive Order 12866 directs each Federal 
agency to propose or adopt a regulation only if the agency makes a 
reasoned determination that the benefits of the intended regulation 
justify its costs. Second, the Regulatory Flexibility Act of 1980 
requires agencies to analyze the economic impact of regulatory changes 
on small entities. Third, the Trade Agreements Act (19 U.S.C. section 
2531-2533) prohibits agencies from setting standards that create 
unnecessary obstacles to the foreign commerce of the United States. In 
developing U.S. standards, this Trade Act requires agencies to consider 
international standards. Where appropriate, agencies are directed to 
use those international standards as the basis of U.S. standards. 
Fourth, the Unfunded Mandates Reform Act of 1995 requires agencies to 
prepare a written assessment of the costs, benefits and other effects 
of proposed or final rules. This requirement applies only to rules that 
include a Federal mandate on State, local, or tribal governments or the 
private sector, likely to result in a total expenditure of $100 million 
or more in any one year (adjusted for inflation).
    In conducting these analyses, the FAA has determined that this 
final rule: (1) Has benefits which do justify its costs, is not a 
``significant regulatory action'' as defined in the Executive Order and 
is not ``significant'' as defined in DOT's Regulatory Policies and 
Procedures; (2) will not have a significant impact on a substantial 
number of small entities; (3) will reduce trade barriers by narrowing 
the difference between United States and Joint Aviation Authority 
regulations; and (4) does not impose an unfunded mandate on State, 
local, or tribal governments, or on the private sector.
    The FAA has placed these analyses in the docket and summarized them 
below.

Comments

    Four parties provided comments in response to the NPRM. Only one 
party, the Aerospace Industries Association (AIA) made any comment on 
the costs associated with the proposal and the reference concerned only 
one of the five broad categories to which AIA addressed its comments. 
In the category entitled ``FAA differences representing additional or 
dissimilar requirements'', AIA lists twelve sections of the NPRM that 
``either are or can easily be interpreted to be different than those in 
Annex 16''.
    The AIA states that ``these differences, if maintained, would also 
make it much more difficult and costly to applicants that might want 
reciprocal approvals by different certificating authorities''. The FAA 
reviewed the sections in question and in some cases was unable to 
determine the specific concern that the commenter was raising.
    In eight of the sections, the FAA views the minor text differences 
as serving to clarify part 36 requirements without introducing any 
additional or dissimilar requirements relative to Annex 16. In the 
ninth section, the FAA concludes that, rather than adding a

[[Page 45208]]

burden, the changed text clarifies that the specified windscreen 
testing need only be performed under certain conditions and does not 
view the section as an additional or dissimilar requirement for ICAO 
Annex 16. The FAA corrected an equation in the tenth section. The FAA 
has been unable to identify any costs associated with ten of the twelve 
sections in question and in view of the lack of any specific cost data 
submitted by the commenter the FAA concludes that there are no 
additional costs associated with these amendments.
    The comments on the two remaining sections in question are beyond 
the scope of this rulemaking. In one case, adoption of the ICAO 
provision would violate United States administrative procedures and in 
the second case, the FAA intends to work within the ICAO process to 
achieve future resolution of the difference.

Analysis of Costs

    The FAA has analyzed the expected costs of this regulatory rule for 
a 10-year period, from 2002 through 2011. As required by the Office of 
Management and Budget (OMB), the present value of this cost stream was 
calculated using a discount factor of 7 percent. All costs in this 
analysis are expressed in 2000 dollars.
    The sections of the final rule that will impose costs fall into 
three categories: (1) Software costs, (2) additional or new measuring 
provisions, and (3) additional reporting requirements.

Software Costs

    Section A36.3.7.6 specifies that the instant in time at which a 
slow time-weighted sound pressure level is characterized should be 0.75 
seconds earlier than the actual readout time. Implementation of this 
change will require modifying the computer software used by the 
applicant. The FAA must verify the software change. The estimated time 
required to make this one-time software change is 40 hours for each 
applicant. The estimated time required by the FAA to verify correct 
implementation of the change is 20 hours for each applicant.
    Based on internal data, the FAA estimates that 11 applicants will 
incur this one-time cost. This is significantly less than the number of 
applicants estimated in the NPRM. The NPRM erroneously included all 
original equipment manufacturers and supplemental type certificate 
applicants as being required to make this software change. The 
estimated cost to the industry is $39,200. The verification cost to the 
FAA is estimated at $17,400. The FAA estimates that these software 
costs will be incurred in the first 3 years of the 10-year period; the 
present value cost to the industry and the FAA will be $34,200 and 
$15,200, respectively.

Measurement Costs

    Section B36.4(b) will add a special requirement for propeller-
driven airplanes that will require the placement of symmetrically 
positioned microphones at each and every test measurement point. 
However, most applicants already take advantage of FAA-approved 
equivalent test procedures that require only one set of symmetrical 
microphones for sideline noise measurements. These equivalent test 
procedures will be unaffected by this change and most applicants are 
expected to continue to use them. If more than a two-microphone array 
were used, however, the cost will be realized as part of the 
certification test performed under the specifications of JAR 36 or ICAO 
Annex 16.
    Industry sources estimate that there are currently six firms 
engaged in the noise certification of large propeller-driven airplanes 
and that all but one are foreign manufacturers that already incur this 
cost if they are not using the approved equivalent procedure. The 
domestic firm is a large entity that probably also already incurs this 
cost under the JAR specifications if it does not use the approved 
equivalent procedures. Therefore, changing part 36 will not result in 
increased costs for known applicants.
    An applicant choosing to use multiple pairs of microphones, 
however, could incur additional costs ranging up to an estimated 
$29,350 per test. The FAA has calculated costs assuming two domestic 
large-propeller applicants will conduct 4 tests meeting this 
requirement over the next 10 years. The total cost is estimated to be 
$117,400, or $83,000 discounted.

Reporting Costs

    Section A36.5.2.5 (c through f, h(2), j) adds five new data 
elements to be reported to the FAA. All of these new reporting 
requirements are already a part of the international standard. Because 
most applicants already address these requirements under JAR 36 or ICAO 
Annex 16, and the data is already reported to the FAA on a voluntary 
basis, minimal cost impact is expected. Additional labor costs for 
documenting data not previously reported are estimated to range from 
$525 to $2,100 per certification.
    Based on FAA estimates, 14 noise certification projects involving 
flight tests are undertaken each year. Four of these projects are 
conducted among the 15 foreign firms that already comply with these new 
reporting requirements under JAR 36 or ICAO Annex 16 and thus will not 
incur additional reporting costs.
    Ten projects are conducted from among the 24 domestic firms engaged 
in flight testing and the FAA estimates that these firms will conduct 
100 tests over the next 10 years. The FAA further estimates that some 
domestic firms will incur additional reporting costs of $1,315 per 
test, based on the midpoint of the estimated additional labor costs 
(($525 + $2,100)/2).
    Domestic firms with a large international presence are estimated to 
conduct 40 of the 100 tests to be conducted over the next 10 years, 
based on the composition of the industry. Because these larger firms 
already frequently comply with the existing international reporting 
standard, the FAA estimates that only 10 of the 40 tests to be 
conducted by these firms will result in the additional reporting costs 
of $1,315 each, or a total of $13,150. The FAA estimates that of the 60 
tests to be conducted by smaller domestic firms, 24 tests will incur 
the additional reporting costs of $1,315 per test or a total of $31,600 
over the next 10 years. Thus, the additional labor costs for reporting 
the additional information will total approximately $44,700 for these 
affected firms.
    It is possible, however, that some applicants might accrue 
additional costs. If an applicant is required to invest in new 
instrumentation or data recording equipment to comply with these 
requirements, the estimated total reporting costs could increase to 
between $5,250 and $10,500 per test. One possible scenario could entail 
the purchase and installation of instrumentation hardware at $4,400, 
plus the labor cost for adding recording capability, and data recording 
and analysis at $3,600 for a total of $8,000 of additional cost. The 
FAA estimates that three domestic firms, one large and two small, could 
incur this additional cost of $7,960 for each test and that each of 
these firms will conduct 4 tests for a total of 12 tests over the next 
10 years at a total cost of $95,520. Thus, the total additional 
reporting costs to the industry will be $140,200, or $98,485 
discounted, based on the minimal additional reporting costs of $44,700 
and $95,520 incurred by the firms requiring additional instrumentation 
and data recording.

Summary of Increased Costs

    The following table summarizes the estimated cost of changing the 
noise

[[Page 45209]]

certification standards of part 36 and achieving greater harmonization 
with the JAA regulations.

                 Total Cost of Final Changes to Part 36
------------------------------------------------------------------------
                                            Total cost     Present value
------------------------------------------------------------------------
Software Costs:
    Industry............................         $39,160         $34,250
    FAA.................................          17,380          15,200
                                         -------------------------------
        Total Software Costs............          56,540          49,450
Measurement Costs.......................         117,400          83,000
Reporting Costs.........................         140,200          98,500
                                         -------------------------------
        Grand Total Costs...............         314,140         230,950
                                         ===============================
        Total Industry Costs............         296,760         215,750
        Total FAA Costs.................          17,380          15,200
------------------------------------------------------------------------

Cost Savings

    Several of the amendments should result in cost savings to 
applicants, depending upon the current inventory of an applicant's test 
equipment and the particular weather circumstances of the flight test. 
Given the uncertainty in the annual number and duration of flight 
tests, however, it is difficult to accurately quantify these savings.
    For example, Section A36.2.2.2(b) will lower the minimum test 
temperature from 36 degrees Fahrenheit to 14 degrees Fahrenheit. One of 
the largest cost elements of the test certification process if the cost 
associated with airplane down time; by extending the temperature range, 
down time should be minimized. Down time occurs when the test aircraft, 
crew, equipment, and technicians are ready to commence testing but 
testing is delayed or postponed because the weather conditions 
specified in Section A36.2 are not met.
    While airplane noise testing is not normally planned for cold 
weather, circumstances may dictate that the test be conducted under 
conditions which could take advantage of this new lower temperature. 
Under this circumstance assuming various scenarios of daily temperature 
patterns that could result in reduced hours of airplane down time, an 
applicant might reduce the total on-site test time of a typical 
certification flight test conducted under these conditions by 10 to 15 
percent.
    As an example of the impact of permitting testing to be conducted 
at a lower temperature, assuming an on-site test time of 5 to 7 days to 
complete a typical certification flight test under these conditions, 
the applicant might reduce the total test time between half a day to 
one full day by testing during a time period when the lower temperature 
condition prevailed. Assuming a cost factor of $157,200 to $209,700 per 
day for larger planes and $73,400 to $146,800 per day for smaller 
airplanes, cost reductions per test made possible by this change in 
minimum test temperatures could range between approximately $78,600 and 
$209,700 for larger airplanes and manufacturers and between $36,700 and 
$146,800 for smaller airplanes and manufacturers. The number of such 
tests conducted under cold weather conditions might be, at most, one 
per applicant over a 10-year period Some applicants might nit encounter 
this situation during a 10-year period.
    Based on the size of the firms conducting noise certifications, the 
FAA estimates that 25 larger applicants will each derive cost savings 
of $144,100 per test and 14 smaller firms will save $91,700 each per 
test, based on the mid-points of the estimated savings ranges. Because 
it is possible that certain applicants may not encounter this situation 
in the 10-year period, however. the FAA has reduced the number of firms 
by three, one large and two small. Thus large firms will save $3.46 
million ($144,100 x 24) and small firms $1.1 million ($91,700 x 12). 
The estimated industry cost savings over ten years totals $4.56 million 
(3.46 + $1.10 million), or $3.2 million discounted.
    Amended section B36.3(a) includes a simplified test procedure that 
may be used in determining the sideline (lateral) noise level for 
propeller-driven large airplanes. This test procedure allows the full 
power noise measurement to be obtained at a point (650m) below the 
takeoff flight path and thus eliminates 40 to 45 fly-bys per test, and 
between 2 and 8 microphone systems depending on the size of the array 
used by the applicant. (Many applicants currently use a 2-microphone 
sideline array.
    In addition to the savings resulting from the reduction in the 
number of fly-bys and the number of microphone systems, further cost 
savings will result from a reduction in site surveying and field set-up 
expenses in addition to the analysis and reporting savings that result 
from fewer fly-bys. The total cost savings of these changes are 
estimated by industry experts at $200,000 to $350,000 per test for 
manufacturers of propeller-driven large airplanes. As an example, based 
on a reduction of 42 fly-bys the midpoint of the estimated range, and 
an example cost of $6,290 per fly-by, cost savings of $264,180 would be 
realized.
    In addition, assuming a reduction of 4 microphone systems, 
including surveying, setup, recording analysis, and reporting at an 
assumed cost factor of $7,340 per system, another $29,360 in savings 
will be realized for a total estimated savings of $293,540 per test 
under this example. The FAA estimates that no more than 10 tests and 
that the derived estimated cost savings will total $2.94 million based 
on a per test savings of $293,540 or $2.06 million discounted.
    Industry sources estimate that cost savings of $26,205 to $52,410 
per year for those applicants with considerable certification activity 
will be realized by the harmonization of testing, data measurement and 
analysis, reporting and documentation, and other noise certification 
efficiencies. Industry sources also claim that these cost savings will 
be achieved by a reduction in the confusion and the multiple 
interpretations that lead to delays and duplicate effort caused by the 
existing dual certification standards. The FAA estimates that 10 firms 
engaged in noise certification activities, each employing 10,000 or 
more workers, will each achieve cost savings of $39,310 (the midpoint 
of the estimated savings) or $393,000 annually for the industry. The 
estimated industry cost savings over ten

[[Page 45210]]

years totals $3.93 million, or $2.76 million discounted.
    The following table summarizes the estimated cost savings of the 
final rulemaking.

                                   Total Cost Savings of Amendments to Part 36
                                            [In millions of dollars]
----------------------------------------------------------------------------------------------------------------
                                                                B36.22.2     B36.3(a)    Efficiency     Total
                                                                savings      savings      savings      savings
----------------------------------------------------------------------------------------------------------------
Savings.....................................................        $4.56        $2.94        $3.93        $11.4
Present Value...............................................         3.20         2.06         2.76         8.02
----------------------------------------------------------------------------------------------------------------

    The FAA has not been able to quantify other potential savings that 
may be made possible by the greater efficiencies and flexibility 
resulting from the uniformity that the final rule provides.

Summary

    When this new final rule becomes effective, U.S. noise 
certification procedures will be nearly uniform with the JAA 
procedures. This harmonization between the test conditions, procedures, 
and noise levels necessary to demonstrate compliance with certification 
requirements for subsonic jet airplanes and subsonic transport category 
large airplanes will result in significant cost savings without 
compromising the environmental benefits of the noise certification 
standards.
    This final rule's estimated cost savings, over ten years, 
(attributable to specific changes to part 36) will be $7.5 million, or 
$5.26 million discounted., In addition, $3.93 million, $2.76 million 
discounted, could be derived from overall efficiencies attributable to 
the harmonization effort in achieving near uniformity of the FAA and 
JAA standards for a total estimated saving of $11.43 million, $8.,02 
million discounted.
    The final rule's cost consist of software costs of $56,500, 
measurement costs of $117,400 and reporting costs of $140,200 for a 
total of $314,100, or $230,900 discounted.

Final Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (Act) establishes ``as a 
principle of regulatory issuance that agencies shall endeavor, 
consistent with the objective of the rule and applicable statues, to 
fit regulatory and informational requirements to the scale of the 
business, organizations, and governmental jurisdictions subject to 
regulation.'' To achieve that principle, the Act requires agencies to 
solicit and consider flexible regulatory proposals and to explain the 
rationale for their actions.
    Agencies must perform a review to determine whether a proposed or 
final rule will have a significant economic impact on a substantial 
number of small entities. If the determination is that it will, the 
agency must prepare a regulatory flexibility analysis (RFA) as 
described in the Act.
    However, if an agency determines that a proposed or final rule is 
not expected to have a significant economic impact on a substantial 
number of small entities, section 605(b) of the Act provides that the 
head of the agency may so certify and an RFA is not required. The 
certification must include a statement providing the factual basis for 
this determination, and the reasoning should be clear.
    Adoption of this final rule will impose costs of $314,000 on the 
FAA and noise certification applicants over the ten year period, of 
which $241,120 is estimated to be incurred by small applicants. Small 
firms will incur software costs of $28,480, measurement costs of 
$117,400, and reporting-related costs of $95,250. This is a 
conservative estimate because it assumes small firms will elect to use 
multiple pairs of microphones to conduct tests when most applicants 
already utilize a less costly equivalent procedure that is FAA-
approved.
    Small firms are firms employing 1,500 employees or fewer based on 
Small Business Administration guidelines. A review of firms engaged in 
noise certification of subsonic jet airplanes and subsonic transport 
category large airplanes found that 14 firms met the criteria. The FAA 
assumes that no more than two small firms will elect to use multiple 
microphone systems to test large-propeller airplanes two times each and 
each will incur measurement costs of $58,700 for a total cost of 
$117,400.
    Additional reporting costs requiring additional instrumentation and 
data recording totaling $63,680 over the ten year period will be 
incurred by two other small applicants or $31,840 each. Additional 
labor costs for new reporting requirements totaling $31,560 over the 10 
year period will be incurred by 6 small firms at a cost to each of 
these smaller firms over the 10 years period of $5,260. Eight small 
noise certification firms will incur one-time software costs of $3,560 
each. Small firms that incur the software charge and also incur labor 
costs to report additional data will have an annualized cost of $770. 
The FAA does not consider these costs to be significant. The highest 
potential annualize cost, $6,700, will be borne by two firms that incur 
both the software and reporting costs ($780, annualized) and also elect 
to use multiple microphones four times each to measure the noise of a 
large propeller-driven airplane ($5,910 annualized).
    The FAA does not have information on the revenues of these two 
potential small entrants but based on information about two small 
current manufacturers the revenue from the sale of one of their 
aircraft ranges from $750,000 to $2.7 million depending on the model. 
If a new entrant sells only a single aircraft each year, the cost of 
this final rule will be less than one percent of the lowest price 
aircraft. Hence, the FAA has determined that the estimated costs of 
compliance are marginal with this final rule are marginal.
    Therefore, the FAA has determined that this final rule will not 
have a significant economic impact to the Regulatory Flexibility Act, 5 
U.S.C. 605(b), the Federal Aviation Administration certifies that this 
rule will not have a significant economic impact on a substantial 
number of small entities.

International Trade Impact Assessment

    The Trade Agreement Act of 1979 prohibits Federal agencies from 
engaging in any standards or related activities that create unnecessary 
obstacles to the foreign commerce of the United States. Legitimate 
domestic objectives, such as safety, are not considered unnecessary 
obstacles. The statute also requires consideration of international 
standards and where

[[Page 45211]]

appropriate, that they be the basis for U.S. standards.
    In accordance with the above statute, the FAA has assessed the 
potential affect of this final rule and has determined that it will 
impose the same costs on domestic and international entities for 
comparable services and thus has a neutral trade impact. It will reduce 
trade barriers by narrowing differences between United States and Joint 
Aviation Authority regulations.

Unfunded Mandates

    The Unfunded Mandates Reform Act of 1995 (the Act), enacted as Pub. 
L. 104-4 on March 22, 1995, is intended, among other things, to curb 
the practice of imposing unfunded Federal mandates on State, local, and 
tribal governments.
    Title II of the Act requires each Federal agency to prepare a 
written statement assessing the effects of any Federal mandate in a 
proposed or final agency rule that may result in a $100 million or more 
expenditure (adjusted annually for inflation) in any one year by State, 
local, and tribal governments, in the aggregate, or by the private 
sector; such a mandate is deemed to be a ``significant regulatory 
action.''
    This rule does not contain such a mandate. Therefore, the 
requirements of Title Ii of the Unfunded Mandates Reform Act of 1995 do 
not apply.

Environmental Assessment

    FAA Order 1050.1D defines FAA actions that may be categorically 
excluded from preparation of a National Environmental Policy Act (NEPA) 
environmental assessment (EA) or environmental impact statement (EIS). 
In accordance with FAA Order 1050.1D, appendix 4, paragraph 4(j), 
regulations, standards, and exemptions (excluding those, which if 
implemented may cause a significant impact on the human environment) 
qualify for a categorical exclusion. The FAA concludes that this final 
rule qualifies for a categorical exclusion because no significant 
impacts to the environment are expected to result from its finalization 
or implementation.

Energy Impact

    The energy impact of the final rule has been assessed in accordance 
with the Energy Policy and Conservation Act (EPCA) Pub. L. 94-163, as 
amended (42 U.S.C. 6362) and FAA Order 1053.1. It has been determined 
that the document is not a major regulatory action under the provision 
of the EPCA.

List of Subjects in 14 CFR Parts 21, 36, and 91

    Aircraft, Noise control.

The Amendment

    In consideration of the foregoing the FAA amends parts 21, 36, and 
91 of Title 14 Code of Federal Regulations, as follows:

PART 21--CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS

    1. The authority citation for part 21 continues to read as follows:

    Authority: 49 U.S.C. 7572, 49 U.S.C. 106(g), 40105, 40113, 
44701-44702, 44707, 44709, 44711, 44713, 44715, 45303.


Sec. 21.93  [Amended]

    2. In paragraph (b)(2) remove the words ``Turbojet powered'' and 
add the words ``Jet (Turbojet powered)'' in its place.


Sec. 21.183  [Amended]

    3. In paragraph (e)(1) remove the words ``turbojet powered'' and 
add the words ``jet (turbojet powered)'' in its place.

PART 36--NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS 
CERTIFICATION

    4. The authority citation for part 36 continues to read as follows:

    Authority: 42 U.S.C. 4321 et seq.; 49 U.S.C. 106(g), 40113, 
44701-44702, 44704, 44715; sec. 305, Pub. L. 96-193, 94 Stat. 50, 
57; E.O. 11513, 35 FR 4247, 3 CFR 1966-1970 Comp., p. 902.


Sec. 36.1  [Amended]

    5. Amend Sec. 36.1 as follows:
    a. In paragraph (a)(1) remove the words ``turbojet powered'' and 
add the word ``jet'' in its place.
    b. In paragraph (b) introductory text remove the words ``turboject 
powered'' and add the word ``jet'' in its place; and remove the 
reference to ``appendix C'' and add ``appendix B'' in its place.
    c. Remove paragraph (d)(3).
    d. In the introductory text of (f) remove the words ``turbojet 
powered'' and add the word ``jet'' in its place.
    e. In paragraph (f)(1) remove the reference to ``C36.5(a)(2)'' and 
add ``B36.5(b)'' in ins place; remove the reference to ``appendix C'' 
and add ``appendix B'' in its place; remove the word ``takeoff'' and 
add the word ``flyover'' in its place; and remove the word ``sideline'' 
and add the word ``lateral'' in its place;
    f. In paragraph (f)(2) remove the word ``takeoff'' and add the word 
``flyover'' in its place; and remove the word ``sideline'' and add the 
word ``lateral'' in its place;
    g. In paragraph (f)(3) remove the reference to ``C36.5(a)(2)'' and 
add ``B36.5(b)'' in its place; and remove the reference to 
``C36.5(a)(3)'' and add ``B36.5(c)'' in its place; and remove all 
references to ``appendix C'' and add ``appendix B'' in its place;
    h. In paragraph (f)(4) remove the reference to ``C36.5'' and add 
``B36.5(b)'' in its place; remove the reference to ``appendix C'' and 
add ``appendix B'' in its place; and add the words ``specified in 
section B36.6'' after ``tradeoff provisions'';
    i. In paragraph (f)(5) remove the reference to ``C36.5(a)(3)'' and 
add ``B36.5(c)'' in its place; remove the reference to ``appendix C'' 
and add ``appendix B'' in its place;
    j. In paragraph (f)(6) remove the reference to ``C36.5'' and add 
``B36.5(c)'' in its place; remove the reference to ``appendix C'' and 
add ``appendix B'' in its place; and add ``appendix B'' in its place; 
and add the words ``specified in section B36.6'' after ``tradeoff 
provisions'';
    k. In paragraph (g) remove the word ``turbojet'' and add the word 
``jet'' in its place.REGTEXT TITLE='14'PART='36'

    6. Revise the heading and Sec. 36.2 to read as follows:


Sec. 36.2  Requirements as of date of application.

    (a) Section 21.17 of this chapter notwithstanding, each person who 
applies for a type certificate for an aircraft covered by this part, 
must show that the aircraft meets the applicable requirements of this 
part that are effective on the date of application for that type 
certificate. When the time interval between the date of application for 
the type certificate and the issuance of the type certificate exceeds 5 
years, the applicant must show that the aircraft meets the applicable 
requirements of this part that were effective on a date, to be selected 
by the applicant, not earlier than 5 years before the issue of the type 
certificate.
    (b) Section 21.101(a) of this chapter notwithstanding, each person 
who applies for an acoustical change to a type design specified in 
Sec. 21.95(b) of this chapter must show compliance with the applicable 
requirements of this part that are effective on the date of application 
for the change in type design. When the time interval between the date 
of application for the change in type design and the issuance of the 
amended or supplemental type certificate exceeds 5 years, the applicant 
must show that the aircraft meets the applicable requirements of this 
part that were effective on a date, to be selected by the applicant, 
not earlier than 5 years before the issue of the amended or 
supplemental type certificate.

[[Page 45212]]

    (c) If an applicant elects to comply with a standard in this part 
that was effective after the filing of the application for a type 
certificate or change to a type design, the election:
    (1) Must be approved by the FAA;
    (2) Must include standards adopted between the date of application 
and the date of the election;
    (3) May include other standards adopted after the standard elected 
by the applicant as determined by the FAA.


Sec. 36.6  [Amended]

    7. Amend Sec. 36.6 as follows:
    a. Add paragraphs (c)(1)(vi) through (x);
    b. Revise paragraphs (d)(1)(i) and (ii), (e)(3)(iii), (e)(3)(vi), 
(e)(3)(vii), and (e)(3)(ix).


Sec. 36.6  Special retroactive requirements.

* * * * *
    (c) * * *
    (1) * * *
    (iv) IEC Publication 61094-3, entitled ``Measurement Microphones--
Part 3: Primary Method for Free-Field Calibration of Laboratory 
Standard Microphones by the Reciprocity Technique'', edition 1.0, dated 
1995.
    (vii) IEC Publication 61094-4, entitled ``Measurement Microphones--
Part 4: Specifications for Working Standard Microphones'', edition 1.0, 
dated 1995.
    (viii) IEC Publication 61260, entitled ``Electroacoustics-Octave-
Band and Fractional-Octave-Band filters'', edition 1.0, dated 1995.
    (ix) IEC Publication 61265, entitled ``Instruments for Measurement 
of Aircraft Nose-Performance Requirements for systems measure one--
Third-Octave-Band Sound pressure Levels in Noise Certification of 
Transport-Category Aeroplanes,'' edition 1.0, dated 1995.
    (x) IEC Publication 60942, entitled ``Electroacoustics--Sound 
Calibrators,'' edition 2.0, dated 1997.
* * * * *
    (d) * * *
    (1) * * *
    (i) International Electrotechnical Commission, 3, rue de Varembe, 
Case postale 131, 1211 Geneva 20, Switzerland.
    (ii) American National Standard Institute, 11 West 42nd Street, New 
York City, New York 10036.
    (e) * * *
    (3) * * *
    (iii) Southern Region Headquarters, 1701 Columbia Avenue, College 
Park, Georgia, 30337.
* * * * *
    (vi) Southwest Region Headquarters, 2601 Meacham Boulevard, Fort 
Worth, Texas, 76137-4298.
    (vii) Northwest Mountain Region Headquarters, 1601 Lind Avenue, 
Southwest, Renton, Washington 98055.
* * * * *
    (ix) Alaskan Region Headquarters, 222 West 7th Avenue, 14, 
Anchorage, Alaska, 99513.
* * * * *


Sec. 36.7  [Amended]

    8. Amend Sec. 36.7 to read as follows:
    a. In the heading of the section and in paragraph (a) remove the 
words ``turbojet powered'' and add the word ``jet'' in its place.
    b. In paragraph (b)(1) remove the reference to ``Appendices A and 
B'' and add ``Appendix A'' in its place.
    c. In paragraph (b)(2) remove the reference to ``C36.5'' and add 
``B36.5'' in its place, remove the reference to ``C36.7'' and add 
``B36.7'' in its place; remove the reference to ``C36.9'' and add 
``B36.8'' in its place; and remove the reference to ``appendix C'' in 
both places it appears and add ``appendix B'' in its place;
    d. In paragraph (c)(1) remove the reference to ``C36.5(b)'' and add 
``B36.6'' in its place; and remove the reference to ``appendix C'' and 
add ``appendix B'' in its place;
    e. In paragraph (c)(2)(ii) remove the words ``takeoff and 
sideline'' and add the words ``flyover and lateral'' in its place;
    f. In paragraph (d)(1) introductory text remove the word 
``turbojet'' and add the word ``jet'' in its place;
    g. In paragraph (d)(1)(ii) remove the reference to ``C36.5(b)'' and 
add ``B36.6'' in its place; and remove the reference to ``appendix C'' 
and add ``appendix B'' in its place;
    h. In paragraph (d)(1)(iii) remove the words ``takeoff and 
sideline'' and add the words ``flyover and lateral'' in its place;
    i. In paragraph (d)(2) introductory text remove the word 
``turbojet'' in both places that it appears and add the word ``jet'' in 
its place.
    j. In paragraph (d)(2)(ii) remove the words ``takeoff and 
sideline'' and add the words ``flyover and lateral'' in its place.

Subpart B--Transport Category Large Airplanes and Jet Airplanes

    9. Revise the heading of Subpart B to read as set forth above.

    10. Revise section 36.101 to read as follows:


Sec. 36.101  Noise measurement and evaluation.

    For transport category large airplanes and jet airplanes, the noise 
generated by the airplane must be measured and evaluated under appendix 
A of this part or under an approved equivalent procedure.

    11. Revise section 36.103 to read as follows:


Sec. 36.103  Noise Limits.

    (a) For subsonic transport category large airplanes and subsonic 
jet airplanes compliance with this section must be shown with noise 
levels measured and evaluated as prescribed in appendix A of this part, 
and demonstrated at the measuring points, and in accordance with the 
test procedures under section B36.8 (or an approved equivalent 
procedure), stated under appendix B of this part.
    (b) Type certification applications for subsonic transport category 
large airplanes and all subsonic jet airplanes must show that the noise 
levels of the airplane are no greater than the Stage 3 noise limits 
stated in section B36.5(c) of appendix B of this part.


36.201 (Subpart C)   [Removed]

    12. Remove and reserve subpart C, consisting of section 36.201.


Sec. 36.301  [Amended]

    13. In paragraph (a) of section 36.301 remove the reference to 
``appendix C'' and add ``appendix B'' in its place.


Sec. 36.1581  [Amended]

    14. Amend Sec. 36.1581 (a)(1) and (d) by removing the words 
``turbojet powered'' and adding the word ``jet'' in its place; in 
paragraph (a)(1) remove the reference to ``appendix C'' and add 
``appendix B'' in its place; and in paragraph (a)(1) remove the words 
``takeoff, sideline'' and add the words ``flyover, lateral'' in its 
place.

    15. Revise appendix A of part 36 to read as follows:

Appendix A to Part 36--Aircraft Noise Measurement and Evaluation Under 
Sec. 36.101

Sec.
A36.1  Introduction.
A36.2  Noise certification test and measurement conditions.
A36.3  Measurement of aircraft noise received on the ground.
A36.4  Calculations of effective perceived noise level from measured 
data.
A36.5  Reporting of data to the FAA.
A36.6  Nomenclature: symbols and units.
A36.7  Sound attenuation in air.
A36.8  [Reserved]
A36.9  Adjustment of airplane flight test results.

Section A36.1  Introduction

    A36.1.1  This appendix prescribes the conditions under which 
airplane noise certification tests must be conducted and

[[Page 45213]]

states the measurement procedures that must be used to measure 
airplane noise. The procedures that must be used to determine the 
noise evaluation quantity designated as effective perceived noise 
level, EPNL, under Secs. 36.101 and 36.803 are also stated.
    A36.1.2  The instructions and procedures given are intended to 
ensure uniformity during compliance tests and to permit comparison 
between tests of various types of airplanes conducted in various 
geographical locations.
    A36.1.3  A complete list of symbols and units, the mathematical 
formulation of perceived noisiness, a procedure for determining 
atmospheric attenuation of sound, and detailed procedures for 
correcting noise levels from non-reference to reference conditions 
are included in this appendix.

Section A36.2  Noise Certification Test and Measurement Conditions

    A36.2.1  General.
    A36.2.1.1  This section prescribes the conditions under which 
noise certification must be conducted and the measurement procedures 
that must be used.

    Note: Many noise certifications involve only minor changes to 
the airplane type design. The resulting changes in noise can often 
be established reliably without resorting to a complete test as 
outlined in this appendix. For this reason, the FAA permits the use 
of approved equivalent procedures. There are also equivalent 
procedures that may be used in full certification tests, in the 
interest of reducing costs and providing reliable results. Guidance 
material on the use of equivalent procedures in the noise 
certification of subsonic jet and propeller-driven large airplanes 
is provided in the current advisory circular for this part.

    A36.2.2  Test environment.
    A36.2.2.1  Locations for measuring noise from an airplane in 
flight must be surrounded by relatively flat terrain having no 
excessive sound absorption characteristics such as might be caused 
by thick, matted, or tall grass, shrubs, or wooded areas. No 
obstructions that significantly influence the sound field from the 
airplane must exist within a conical space above the point on the 
ground vertically below the microphone, the cone being defined by an 
axis normal to the ground and by a half-angle 80 deg. from this 
axis.

    Note: Those people carrying out the measurements could 
themselves constitute such obstruction.

    A36.2.2.2  The tests must be carried out under the following 
atmospheric conditions.
    (a) No precipitation;
    (b) Ambient air temperature not above 95 deg.F (35 deg.C) and 
not below 14 deg.F (-10 deg.C), and relative humidity not above 95% 
and not below 20% over the whole noise path between a point 33 ft 
(10 m) above the ground and the airplane;

    Note: Care should be taken to ensure that the noise measuring, 
airplane flight path tracking, and meteorological instrumentation 
are also operated within their specific environmental limitations.

    (c) Relative humidity and ambient temperature over the whole 
noise path between a point 33 ft (10 m) above the ground and the 
airplane such that the sound attenuation in the one-third octave 
band centered on 8 kHz will not be more than 12 dB/100 m unless:
    (1) The dew point and dry bulb temperatures are measured with a 
device which is accurate to 0.9 deg.F 
(0.5 deg.C) and used to obtain relative humidity; in 
addition layered sections of the atmosphere are used as described in 
section A36.2.2.3 to compute equivalent weighted sound attenuations 
in each one-third octave band; or
    (2) The peak noy values at the time of PNLT, after adjustment to 
reference conditions, occur at frequencies less than or equal to 400 
Hz.;
    (d) If the atmospheric absorption coefficients vary over the 
PNLTM sound propagation path by more than 1.6 dB/1000 ft 
(0.5 dB/100m) in the 3150Hz one-third octave band from 
the value of the absorption coefficient derived from the 
meteorological measurement obtained at 33 ft (10 m) above the 
surface, ``layered'' sections of the atmosphere must be used as 
described in section A36.2.2.3 to compute equivalent weighted sound 
attenuations in each one-third octave band; the FAA will determine 
whether a sufficient number of layered sections have been used. For 
each measurement, where multiple layering is not required, 
equivalent sound attenuations in each one-third octave band must be 
determined by averaging the atmospheric absorption coefficients for 
each such band at 33 ft (10 m) above ground level, and at the flight 
level of the airplane at the time of PNLTM, for each measurement;
    (e) Average wind velocity 33 ft (10 m) above ground may not 
exceed 12 knots and the crosswind velocity for the airplane may not 
exceed 7 knots. The average wind velocity must be determined using a 
30-second averaging period spanning the 10 dB-down time interval. 
Maximum wind velocity 33 ft (10 m) above ground is not to exceed 15 
knots and the crosswind velocity is not to exceed 10 knots during 
the 10 dB-down time interval;
    (f) No anomalous meteorological or wind conditions that would 
significantly affect the measured noise levels when the noise is 
recorded at the measuring points specified by the FAA; and
    (g) Meteorological measurements must be obtained within 30 
minutes of each noise test measurement; meteorological data must be 
interpolated to actual times of each noise measurement.
    A36.2.2.3  When a multiple layering calculation is required by 
section A36.2.2.2(c) or A36.2.2.2(d) the atmosphere between the 
airplane and 33 ft (10 m) above the ground must be divided into 
layers of equal depth. The depth of the layers must be set to not 
more than the depth of the narrowest layer across which the 
variation in the atmospheric absorption coefficient of the 3150 Hz 
one-third octave band is not greater than 1.6 dB/1000 ft 
(0.5 dB/100m), with a minimum layer depth of 100 ft (30 
m). This requirement must be met for the propagation path at PNLTM. 
The mean of the values of the atmospheric absorption coefficients at 
the top and bottom of each layer may be used to characterize the 
absorption properties of each layer.
    A36.2.2.4  The airport control tower or another facility must be 
aproved by the FAA for use as the central location at which 
measurements of atmospheric parameters are representative of those 
conditions existing over the geographical area in which noise 
measurements are made.
    A36.2.3  Flight path measurement.
    A36.2.3.1  The airplane height and lateral position relative to 
the flight track must be determined by a method independent of 
normal flight instrumentation such as radar tracking, theodolite 
triangulation, or photographic scaling techniques, to be approved by 
the FAA.
    A36.2.3.2  The airplane position along the flight path must be 
related to the noise recorded at the noise measurement locations by 
means of synchronizing signals over a distance sufficient to assure 
adequate data during the period that the noise is within 10 dB of 
the maximum value of PNLT.
    A36.2.3.3  Position and performance data required to make the 
adjustments referred to in section A36.9 of this appendix must be 
automatically recorded at an approved sampling rate. Measuring 
equipment must be approved by the FAA.

Section A36.3  Measurement of Airplane Noise Received on the Ground

    A36.3.1  Definitions.
    For the purposes of section A36.3 the following definitions 
apply:
    A36.3.1.1  Measurement system means the combination of 
instruments used for the measurement of sound pressure levels, 
including a sound calibrator, windscreen, microphone system, signal 
recording and conditioning devices, and one-third octave band 
analysis system.

    Note: Practical installations may include a number of microphone 
systems, the outputs from which are recorded simultaneously by a 
multi-channel recording/analysis device via signal conditioners, as 
appropriate. For the purpose of this section, each complete 
measurement channel is considered to be a measurement system to 
which the requirements apply accordingly.

    A36.3.1.2  Microphone system means the components of the 
measurement system which produce an electrical output signal in 
response to a sound pressure input signal, and which generally 
include a microphone, a preamplifier, extension cables, and other 
devices as necessary.
    A36.3.1.3  Sound incidence angle means in degrees, an angle 
between the principal axis of the microphone, as defined in IEC 
61094-3 and IEC 61094-4, as amended and a line from the sound source 
to the center of the diaphragm of the microphone.

    Note: When the sound incidence angle is 0 deg., the sound is 
said to be received at the microphone at ``normal (perpendicular) 
incidence;'' when the sound incidence angle is 90 deg., the sound is 
said to be received at ``grazing incidence.''

    A36.3.1.4  Reference direction means, in degrees, the direction 
of sound incidence specified by the manufacturer of the microphone, 
relative to a sound incidence angle of 0 deg., for which the free-
field sensitivity level of the microphone system is within specified 
tolerance limits.

[[Page 45214]]

    A36.3.1.5  Free-field sensitivity of a microphone system means, 
in volts per Pascal, for a sinusoidal plane progressive sound wave 
of specified frequency, at a specified sound incidence angle, the 
quotient of the root means square voltage at the output of a 
microphone system and the root mean square sound pressure that would 
exist at the position of the microphone in its absence.
    A36.3.1.6  Free-field sensitivity level of a microphone system 
means, in decibels, twenty times the logarithm to the base ten of 
the ratio of the free-field sensitivity of a microphone system and 
the reference sensitivity of one volt per Pascal.

    Note: The free-field sensitivity level of a microphone system 
may be determined by subtracting the sound pressure level (in 
decibels re 20 [mu]Pa) of the sound incident on the microphone from 
the voltage level (in decibels re 1 V) at the output of the 
microphone system, and adding 93.98 dB to the result.

    A36.3.1.7  Time-average band sound pressure level means in 
decibels, ten times the logarithm to the base ten, of the ratio of 
the time mean square of the instantaneous sound pressure during a 
stated time interval and in a specified one-third octave band, to 
the square of the reference sound pressure of 20 [mu]Pa.
    A36.3.1.8  Level range means, in decibels, an operating range 
determined by the setting of the controls that are provided in a 
measurement system for the recording and one-third octave band 
analysis of a sound pressure signal. The upper boundary associated 
with any particular level range must be rounded to the nearest 
decibel.
    A36.3.1.9  Calibration sound pressure level means, in decibels, 
the sound pressure level produced, under reference environmental 
conditions, in the cavity of the coupler of the sound calibrator 
that is used to determine the overall acoustical sensitivity of a 
measurement system.
    A36.3.1.10  Reference level range means, in decibels, the level 
range for determining the acoustical sensitivity of the measurement 
system and containing the calibration sound pressure level.
    A36.3.1.11  Calibration check frequency means, in hertz, the 
nominal frequency of the sinusoidal sound pressure signal produced 
by the sound calibrator.
    A36.3.1.12  Level difference means, in decibels, for any nominal 
one-third octave midband frequency, the output signal level measured 
on any level range minus the level of the corresponding electrical 
input signal.
    A36.3.1.13  Reference level difference means, in decibels, for a 
stated frequency, the level difference measured on a level range for 
an electrical input signal corresponding to the calibration sound 
pressure level, adjusted as appropriate, for the level range.
    A36.3.1.14  Level non-linearity means, in decibels, the level 
difference measured on any level range, at a stated one-third octave 
nominal midband frequency, minus the corresponding reference level 
difference, all input and output signals being relative to the same 
reference quantity.
    A36.3.1.15  Linear operating range means, in decibels, for a 
stated level range and frequency, the range of levels of steady 
sinusoidal electrical signals applied to the input of the entire 
measurement system, exclusive of the microphone but including the 
microphone preamplifier and any other signal-conditioning elements 
that are considered to be part of the microphone system, extending 
from a lower to an upper boundary, over which the level non-
linearity is within specified tolerance limits.

    Note: Microphone extension cables as configured in the field 
need not be included for the linear operating range determination.

    A36.3.1.16  Windscreen insertion loss means, in decibels, at a 
stated nominal one-third octave midband frequency, and for a stated 
sound incidence angel on the inserted microphone, the indicated 
sound pressure level without the windscreen installed around the 
microphone minus the sound pressure level with the windscreen 
installed.
    A36.3.2  Reference environmental conditions.
    A36.3.2.1  The reference environmental conditions for specifying 
the performance of a measurement system are:
    (a) Air temperature 73.4 deg.F (23 deg.C);
    (b) Static air pressure 101.325 kPa; and
    (c) Relative humidity 50%.
    A36.3.3.  General.

    Note: Measurements of aircraft noise that are made using 
instruments that conform to the specifications of this section will 
yield one-third octave band sound pressure levels as a function of 
time. These one-third octave band levels are to be used for the 
calculation of effective perceived noise level as described in 
section A36.4.

    A36.3.3.1  The measurement system must consist of equipment 
approved by the FAA and equivalent to the following:
    (a) A windscreen (See A36.3.4.);
    (b) A microphone system (See A36.3.5):
    (c) A recording and reproducing system to store the measured 
aircraft noise signals for subsequent analysis (see A36.3.6);
    (d) A one-third octave band analysis system (see A36.3.7); and
    (e) Calibration systems to maintain the acoustical sensitivity 
of the above systems within specified tolerance limits (see 
A36.3.8).
    A36.3.3.2.  For any component of the measurement system that 
converts an analog signal to digital form, such conversion must be 
performed so that the levels of any possible aliases or artifacts of 
the digitization process will be less than the upper boundary of the 
linear operating range by at least 50 dB at any frequency less than 
12.5 kHz. The sampling rate must be at least 28 kHz. An anti-
aliasing filter must be included before the digitization process.
    A36.3.4  Windscreen.
    A36.3.4.1  In the absence of wind and for sinusoidal sounds at 
grazing incidence, insertion loss caused by the windscreen of a 
stated type installed around the microphone must not exceed 
1.5 dB at nominal one-third octave midband frequencies 
from 50 Hz to 10 kHz inclusive.
    A36.3.5  Microphone system.
    A36.3.5.1  The microphone system must meet the specifications in 
sections A36.3.5.2 to A36.3.5.4. Various microphone systems may be 
approved by the FAA on the basic of demonstrated equivalent overall 
electroacoustical performance. Where two or more microphone systems 
of the same type are used, demonstration that at least one system 
conforms to the specifications in full is sufficient to demonstrate 
conformance.

    Note: An applicant must still calibrate and check each system as 
required in section A36.3.9.

    A36.3.5.2  The microphone must be mounted with the sensing 
element 4 ft (1.2 m) above the local ground surface and must be 
oriented for grazing incidence, i.e., with the sensing element 
substantially in the plane defined by the predicted reference flight 
path of the aircraft and the measuring station. The microphone 
mounting arrangement must minimize the interference of the supports 
with the sound to be measured. Figure A36-1 illustrates sound 
incidence angles on a microphone.
    A36.3.5.3  The free-field sensitivity level of the microphone 
and preamplifier in the reference direction, at frequencies over at 
least the range of one-third-octave nominal midband frequencies from 
50 Hz to 5 kHz inclusive, must be within 1.0 dB of that 
at the calibration check frequency, and within 2.0 dB 
for nominal midband frequencies of 6.3 kHz, 8 kHz and 10 kHz.
    A36.3.5.4  For sinusoidal sound waves at each one-third octave 
nominal midband frequency over the range from 50 Hz to 10 kHz 
inclusive, the free-field sensitivity levels of the microphone 
system at sound incidence angles of 30 deg., 60 deg., 90 deg., 
120 deg. and 150 deg., must not differ from the free-field 
sensitivity level at a sound incidence angle of 0 deg. (``normal 
incidence'') by more than the values shown in Table A36-1. The free-
field sensitivity level differences at sound incidence angles 
between any two adjacent sound incidence angles in Table A36-1 must 
not exceed the tolerance limit for the greater angle.

[[Page 45215]]

[GRAPHIC] [TIFF OMITTED] TR08JY02.000

    A36.3.6  Recording and reproducing systems.
    A36.3.6.1  A recording and reproducing system, such as a digital 
or analog magnetic tape recorder, a computer-based system or other 
permanent data storage device, must be used to store sound pressure 
signals for subsequent analysis. The sound produced by the aircraft 
must be recorded in such away that a record of the complete 
acoustical signal is retained. The recording and reproducing systems 
must meet the specifications in sections A36.3.6.2 to A36.3.6.9 at 
the recording speeds and/or data sampling rates used for the noise 
certification tests. Conformance must be demonstrated for the 
frequency bandwidths and recording channels selected for the tests.
    A36.3.6.2  The recording and reproducing systems must be 
calibrated as described in section A36.3.9.
    (a) For aircraft noise signals for which the high frequency 
spectral levels decrease rapidly with increasing frequency, 
appropriate pre-emphasis and complementary de-emphasis networks may 
be included in the measurement system. If pre-emphasis is included, 
over the range of nominal one-third octave midband frequencies from 
800 Hz to 10 kHz inclusive, the electrical gain provided by the pre-
emphasis network must not exceed 20 dB relative to the gain at 800 
Hz.
    A36.3.6.3  For steady sinusoidal electrical signals applied to 
the input of the entire measurement system including all parts of 
the microphone system except the microphone at a selected signal 
level within 5 dB of that corresponding to the calibration sound 
pressure level on the reference level range, the time-average signal 
level indicated by the readout device at any one-third octave 
nominal midband frequency from 50 Hz to 10 kHz inclusive must be 
within 1.5 dB of that at the calibration check 
frequency. The Frequency response of a measurement system, which 
includes components that convert analog signals to digital form, 
must be within 0.3 dB of the response at 10 kHz over the 
frequency range from 10 kHz to 11.2 kHz.

    Note: Microphone extension cables as configured in the field 
need not be included for the frequency response determination. This 
allowance does not eliminate the requirement of including microphone 
extension cables when performing the pink noise recording in section 
A36.3.9.5.

    A36.3.6.4  For analog tape recordings, the amplitude 
fluctuations of a 1 kHz sinusoidal signal recorded within 5 dB of 
the level corresponding to the calibration sound pressure level must 
not vary by more than 0.5 dB throughout any reel of the 
type of magnetic tape used. Conformance to this requirement must be 
demonstrated using a device that has time-averaging properties 
equivalent to those of the spectrum analyzer.
    A36.3.6.5  For all appropriate level ranges and for steady 
sinusoidal electrical signals applied to the input of the 
measurement system, including all parts of the microphone

[[Page 45216]]

system except the microphone, at one-third-octave nominal midband 
frequencies of 50 Hz, 1 kHz and 10 kHz, and the calibration check 
frequency, if it is not one of these frequencies, the level non-
linearity must not exceed 0.5 dB for a linear operating 
range of at least 50 dB below the upper boundary of the level range.

    Note 1: Level linearity of measurement system components may be 
tested according to the methods described in IEC 61265 as amended.


    Note 2: Microphone extension cables configured in the field need 
not be included for the level linearity determination.

    A36.3.6.6  On the calibration sound pressure level must be at 
least 5 dB, but no more than 30 dB less than the upper boundary of 
the level range.
    A36.3.6.7  The linear operating ranges on adjacent level ranges 
must overlap by at least 50 dB minus the change in attenuation 
introduced by a change in the level range controls.

    Note: It is possible for a measurement system to have level 
range controls that permit attenuation changes of either 10 dB or 1 
dB, for example. With 10 dB steps, the minimum overlap required 
would be 40 dB, and with 1 dB steps the minimum overlap would be 49 
dB.

    A36.3.6.8  An overload indicator must be included in the 
recording and reproducing systems so that an overload indication 
will occur during an overload condition on any relevant level range.
    A36.3.6.9  Attenuators included in the measurement system to 
permit range changes must operate in known intervals of decibel 
steps.
    A36.3.6.7  Analysis systems.
    A36.3.7.1  The analysis system must conform to the 
specifications in sections A36.3.7.2 to A36.3.7.7 for the frequency 
bandwidths, channel configurations and gain settings used for 
analysis.
    A36.3.7.2 The output of the analysis system must consist of one-
third octave band sound pressure levels as a function of time, 
obtained by processing the noise signals (preferably recorded) 
through an analysis system with the following characteristics:
    (a) A set of 24 one-third octave band filters, or their 
equivalent, having nominal midband frequencies from 50 Hz to 10 kHz 
inclusive;
    (b) Response and averaging properties in which, in principle, 
the output from any one-third octave filter band is squared, 
averaged and displayed or stored as time-averaged sound pressure 
levels;
    (c) The interval between successive sound pressure level samples 
must be 500 ms 5 milliseconds(ms) for spectral analysis 
with or without slow time-weighting, as defined in section 
A36.3.7.4;
    (d) For those analysis systems that do not process the sound 
pressure signals during the period of time required for readout and/
or resetting of the analyzer, the loss of data must not exceed a 
duration of 5 ms; and
    (e) The analysis system must operate in real time from 50 Hz 
through at least 12 kHz inclusive. This requirement applies to all 
operating channels of a multi-channel spectral analysis system.
    A36.3.7.3  The minimum standard for the one-third octave band 
analysis system is the class 2 electrical performance requirements 
of IEC 61260 as amended, over the range of one-third octave nominal 
midband frequencies from 50 Hz through 10 kHz inclusive.

    Note: IEC 61260 specifies procedures for testing of one-third 
octave band analysis systems for relative attenuation, anti-aliasing 
filters, real time operation, level linearity, and filter integrated 
response (effective bandwidth).

    A36.3.7.4  When slow time averaging is performed in the 
analyzer, the response of the one-third octave band analysis system 
to a sudden onset or interruption of a constant sinusoidal signal at 
the respective one-third octave nominal midband frequency, must be 
measured at sampling instants 0.5, 1, 1.5 and 2 seconds(s) after the 
onset and 0.5 and is after interruption. The rising response must be 
-4 1 dB at 0.5s, -1.75 0.75 dB at 1s, -1 
0.5 dB at 1.5s and -0.5 0.5 dB at 2s 
relative to the steady-state level. The failing response must be 
such that the sum of the output signal levels, relative to the 
initial steady-state level, and the corresponding rising response 
reading is -6.5 1 dB, at both 0.5 and 1s. At subsequent 
times the sum of the rising and failing responses must be -7.5 dB or 
less. This equates to an exponential averaging process (slow time-
weighting) with a nominal 1s time constant (i.e., 2s averaging 
time).
    A36.3.7.5  When the one-third octave band sound pressure levels 
are determined from the output of the analyzer without slow time-
weighting, slow time-weighting must be simulated in the subsequent 
processing. Simulated slow time-weighted sound pressure levels can 
be obtained using a continuous exponential averaging process by the 
following equation:

Ls (i,k) = 10 log [(0.60653) 
100.1 Ls[i, (k-1)] + (0.39347) 100.1 L (i, k)]

where Ls(i,k) is the simulated slow time-weighted sound 
pressure level and L(i,k) is the as-measured 0.5s time average sound 
press level determined from the output of the analyzer for the k-th 
instant of time and i-th one-third octave band. For k=1, the slow 
time-weighted sound pressure Ls[i, (k-1=0)] on the right 
hand side should be set to 0 dB. An approximation of the continuous 
exponential averaging is represented by the following equation for a 
four sample averaging process for k [ge] 4:

Ls (i,k) = 10 log [(0.13) 100.1L[i,(k-3)] + 
(0.21) 100.1 L[i, (k-2)] + (0.27) 
100.1 L[i, (k-1)] + (0.39) 100.1 L[i, k]]

where Ls (i, k) is the simulated slow time-weighted sound 
pressure level and L (i, k) is the as measured 0.5s time average 
sound pressure level determined from the output of the analyzer for 
the k-th instant of time and the i-th one-third octave band.
    The sum of the weighting factors is 1.0 in the two equations. 
Sound pressure levels calculated by means of either equation are 
valid for the sixth and subsequent 0.5s data samples, or for times 
greater than 2.5s after initiation of data analysis.

    Note: The coefficients in the two equations were calculated for 
use in determining equivalent slow time-weighted sound pressure 
levels from samples of 0.5s time average sound pressure levels. The 
equations do not work with data samples where the averaging time 
differs from 0.5s.

    A36.3.76  The instant in time by which a slow time-weighted 
sound pressure level is characterized must be 0.75s earlier than the 
actual readout time.

    Note: The definition of this instant in time is needed to 
correlate the recorded noise with the aircraft position when the 
noise was emitted and takes into account the averaging period of the 
slow time-weighting. For each 0.5 second data record this instant in 
time may also be identified as 1.25 seconds after the start of the 
associated 2 second averaging period.

    A36.3.7.7  The resolution of the sound pressure levels, both 
displayed and stored, must be 0.1 dB or finer.
    A36.3.8  Calibration systems.
    A36.3.8.1  The acoustical sensitivity of the measurement system 
must be determined using a sound calibrator generating a known sound 
pressure level at a known frequency. The minimum standard for the 
sound calibrator is the class 1L requirements of IEC 60942 as 
amended.
    A36.3.9  Calibration and checking of system.
    A36.3.9.1  Calibration and checking of the measurement system 
and its constituent components must be carried out to the 
satisfaction of the FAA by the methods specified in sections 
A36.3.9.2 through A36.3.9.10. The calibration adjustments, including 
those for environmental effects on sound calibrator output level, 
must be reported to the FAA and applied to the measured one-third-
octave sound pressure levels determined from the output of the 
analyzer. Data collected during an overload indication are invalid 
and may not be used. If the overload condition occurred during 
recording, the associated test data are invalid, whereas if the 
overload occurred during analysis, the analysis must be repeated 
with reduced sensitivity to eliminate the overload.
    A36.3.9.2  The free-field frequency response of the microphone 
system may be determined by use of an electrostatic actuator in 
combination with manufacturer's data or by tests in an anechoic 
free-field facility. The correction for frequency response must be 
determined within 90 days of each test series. The correction for 
non-uniform frequency response of the microphone system must be 
reported to the FAA and applied to the measured one-third octave 
band sound pressure levels determined from the output of the 
analyzer.
    A36.3.9.3  When the angles of incidence of sound emitted from 
the aircraft are within 30 deg. of razing incidence at 
the microphone (see Figure A36-1), a single set of free-field 
corrections based on grazing incidence is considered sufficient for 
correction of directional response effects. For other cases, the 
angle of incidence for each 0.5 second sample must be determined and 
applied for the correction of incidence effects.
    A36.3.9.4  For analog magnetic tape recorders, each reel of 
magnetic tape must carry at least 30 seconds of pink random or 
pseudo-random noise at its beginning and

[[Page 45217]]

end. Data obtained from analog tape-recorded signals will be 
accepted as reliable only if level differences in the 10 kHz one-
third-octave-band are not more than 0.75 dB for the signals recorded 
at the beginning and end.
    A36.3.9.5  The frequency response of the entire measurement 
system while deployed in the field during the test series, exclusive 
of the microphone, must be determined at a level within 5 dB of the 
level corresponding to the calibration sound pressure level on the 
level range used during the tests for each one-third octave nominal 
midband frequency from 50 Hz to 10 kHz inclusive, utilizing pink 
random or pseudo-random noise. Within six months of each test series 
the output of the noise generator must be determined by a method 
traceable to the U.S. National Institute of Standards and Technology 
or to an equivalent national standards laboratory as determined by 
the FAA. Changes in the relative output from the previous 
calibration at each one-third octave band may not exceed 0.2 dB. The 
correction for frequency response must be reported to the FAA and 
applied to the measured one-third octave sound pressure levels 
determined from the output of the analyzer.
    A36.3.9.6  The performance of switched attenuators in the 
equipment used during noise certification measurements and 
calibration must be checked within six months of each test series to 
ensure that the maximum error does not exceed 0.1 dB.
    A36.3.9.7  The sound pressure level produced in the cavity of 
the coupler of the sound calibrator must be calculated for the test 
environmental conditions using the manufacturer's supplied 
information on the influence of atmospheric air pressure and 
temperature. This sound pressure level is used to establish the 
acoustical sensitivity of the measurement system. Within six months 
of each test series the output of the sound calibrator must be 
determined by a method traceable to the U.S. National Institute of 
Standards and Technology or to an equivalent national standards 
laboratory as determined by the FAA. Changes in output from the 
previous calibration must not exceed 0.2 dB.
    A36.3.9.8  Sufficient sound pressure level calibrations must be 
made during each test day to ensure that the acoustical sensitivity 
of the measurement system is know at the prevailing environmental 
conditions corresponding with each test series. The differences 
between the acoustical sensitivity levels recorded immediately 
before and immediately after each test series on each day may not 
exceed 0.5 dB. The 0.5 dB limit applies after any atmospheric 
pressure corrections have been determined for the calibrator output 
level. The arithmetic mean of the before and after measurements must 
be used to represent the acoustical sensitivity level of the 
measurement system for that test series. The calibration corrections 
must be reported to the FAA and applied to the measured one-third 
octave band sound pressure levels determined from the output of the 
analyzer.
    A36.3.9.9  Each recording medium, such as a reel, cartridge, 
cassette, or diskette, must carry a sound pressure level calibration 
of at least 10 seconds duration at its beginning and end.
    A36.3.9.10  The free-field insertion loss of the windscreen for 
each one-third octave nominal midband frequency from 50 Hz to 10 kHz 
inclusive must be determined with sinusoidal sound signals at the 
incidence angles determined to be applicable for correction of 
directional response effects per section A36.3.9.3. The interval 
between angles tested must not exceed 30 degrees. For a windscreen 
that is undamaged and uncontaminated, the insertion loss may be 
taken from manufacturer's data. Alternatively, within six months of 
each test series the insertion loss of the windscreen may be 
determined by a method traceable to the U.S. National Institute of 
Standards and Technology or an equivalent national standards 
laboratory as determined by the FAA. Changes in the insertion loss 
from the previous calibration at each one-third-octave frequency 
band must note exceed 0.4 dB. The correction for the free-field 
insertion loss of the windscreen must be reported to the FAA and 
applied to the measured one-third octave sound pressure levels 
determined from the output of the analyzer.
    A36.3.10  Adjustments for ambient noise.
    A36.3.10.1  Ambient noise, including both a acoustical 
background and electrical noise of the measurement system, must be 
recorded for at least 10 seconds at the measurement points with the 
system gain set at the levels used for the aircraft noise 
measurements. Ambient noise must be representative of the acoustical 
background that exists during the flyover test run. The recorded 
aircraft noise data is acceptable only if the ambient noise levels, 
when analyzed in the same way, and quoted in PNL (see A36.4.1.3 
(a)), are at least 20 dB below the maximum PNL of the aircraft.
    A36.3.10.2  Aircraft sound pressure levels within the 10 dB-down 
points (see A36.4.5.1) must exceed the mean ambient noise levels 
determined in section A36.3.10.1 by at least 3 dB in each one-third 
octave band, or must be adjusted using a method approved by the FAA; 
one method is described in the current advisory circular for this 
part.

Section A36.4  Calculation of Effective Perceived Noise Level From 
Measured Data

    A36.4.1  General.
    A36.4.1.1  The basic element for noise certification criteria is 
the noise evaluation measure known as effective perceived noise 
level, EPNL, in units of EPNdB, which is a single number evaluator 
of the subjective effects of airplane noise on human beings. EPNL 
consists of instantaneous perceived noise level, PNL, corrected for 
spectral irregularities, and for duration. The spectral irregularity 
correction, called ``tone correction factor'', is made at each time 
increment for only the maximum tone.
    A36.4.1.2  Three basic physical properties of sound pressure 
must be measured: level, frequency distribution, and time variation. 
To determine EPNL, the instantaneous sound pressure level in each of 
the 24 one-third octave bands is required for each 0.5 second 
increment of time during the airplane noise measurement.
    A36.4.1.3  The calculation procedure that uses physical 
measurements of noise to derive the EPNL evaluation measure of 
subjective response consists of the following five steps:
    (a) The 24 one-third octave bands of sound pressure level are 
converted to perceived noisiness (noy) using the method described in 
section A36.4.2.1 (a). The noy values are combined and then 
converted to instantaneous perceived noise levels, PNL(k).
    (b) A tone correction factor C(k) is calculated for each 
spectrum to account for the subjective response to the presence of 
spectral irregularities.
    (c) The tone correction factor is added to the perceived noise 
level to obtain tone-corrected perceived noise levels PNLT(k), at 
each one-half second increment:

PNLT(k) = PNL(k) + C(k)

The instantaneous values of tone-corrected perceived noise level are 
derived and the maximum value, PNLTM, is determined.
    (d) A duration correction factor, D, is computed by integration 
under the curve of tone-corrected perceived noise level versus time.
    (e) Effective perceived noise level, EPNL, is determined by the 
algebraic sum of the maximum tone-corrected perceived noise level 
and the duration correction factor:

EPNL = PNLTM + D

    A36.4.2  Perceived noise level.
    A36.4.2.1  Instantaneous perceived noise levels, PNL(k), must be 
calculated from instantaneous one-third octave band sound pressure 
levels, SPL(i, k) as follows:
    (a) Step 1: For each one-third octave band from 50 through 
10,000 Hz, convert SPL(i, k) to perceived noisiness n(i, k), by 
using the mathematical formulation of the noy table given in section 
A36.4.7.
    (b) Step 2: Combine the perceived noisiness values, n(i, k), 
determined in step 1 by using the following formula:
[GRAPHIC] [TIFF OMITTED] TR08JY02.001

where n(k) is the largest of the 24 values of n(i, k) and N(k) is 
the total perceived noisiness.
    (c) Step 3: Convert the total perceived noisiness, N(k), 
determined in Step 2 into perceived noise level, PNL(k), using the 
following formula:
[GRAPHIC] [TIFF OMITTED] TR08JY02.002


    Note: PNL(k) is plotted in the current advisory circular for 
this part.

    A36.4.3  Correction for spectral irregularities.
    A36.4.3.1  Noise having pronounced spectral irregularities (for 
example, the maximum discrete frequency components or tones) must be 
adjusted by the correction factor C(k) calculated as follows:
    (a) Step 1: After applying the corrections specified under 
section A36.3.9, start with the sound pressure level in the 80 Hz 
one-third octave band (band number 3), calculate

[[Page 45218]]

the changes in sound pressure level (or ``slopes'') in the remainder 
of the one-third octave bands as follows:

s(3,k)=no value
s(4,k)=SPL(4,k)-SPL(3,k)


s(i,k)=SPL(i,k)-SPL(i-1,k)


s(24,k)=SPL(24,k)-SPL(23,k)

    (b) Step 2: Encircle the value of the slope, s(i, k), where the 
absolute value of the change in slope is greater than five; that is 
where:

[bond][Delta](i,k)[bond]=[bond]s(i,k)-s(i-1,k)[bond]5

    (c) Step 3:
    (1) If the encircled value of the slope s(i, k) is positive and 
algebraically greater than the slope s(i-1, k) encircle SPL(i, k).
    (2) If the encircled value of the slope s(i, k) is zero or 
negative and the slope s(i-1, k) is positive, encircle SPL(i-1, k).
    (3) For all other cases, no sound pressure level value is to be 
encircled.
    (d) Step 4: Compute new adjusted sound pressure levels SPL'(i, 
k) as follows:
    (1) For non-encircled sound pressure levels, set the new sound 
pressure levels equal to the original sound pressure levels, SPL'(i, 
k) = SPL(i, k).
    (2) For encircled sound pressure levels in bands 1 through 23 
inclusive, set the new sound pressure level equal to the arithmetic 
average of the preceding and following sound pressure levels as 
shown below:

SPL'(i,k)=\1/2\[SPL(i-1,k)+SPL(i+1,k)]

    (3) If the sound pressure level in the highest frequency band (i 
= 24) is encircled, set the new sound pressure level in that band 
equal to:

SPL'(24,k)=SPL(23,k)+s(23,k)

    (e) Step 5: Recompute new slope s'(i, k), including one for an 
imaginary 25th band, as follows:

s'(3,k)=s'(4,k)
s'(4,k)=SPL'(4,k)-SPL'(3,k)


s'(i,k)=SPL'(i,k)-SPL'(i-1,k)


s'(24,k)=SPL'(24,k)-SPL'(23,k)
s'(25,k)=s'(24,k)

    (f) Step 6: For i, from 3 through 23, compute the arithmetic 
average of the three adjacent slopes as follows:

s(i,k)=\1/3\[s'(i,k)+s'(i+1,k)+s'(i+2,k)]

    (g) Step 7: Compute final one-third octave-band sound pressure 
levels, SPL'' (i,k), by beginning with band number 3 and proceeding 
to band number 24 as follows:

    SPL''(3,k)=SPL(3,k)
    SPL''(4,k)=SPL''(3,k)+s(3,k)
    
    
    SPL''(i,k)=SPL''(i-1,k)+s(i-1,k)
    
    
    SPL''(24,k)=SPL''(23,k)+s(23,k)

    (h) Setp 8: Calculate the differences, F (i,k), between the 
original sound pressure level and the final background sound 
pressure level as follows:
F(i,k)=SPL(i,k)-SPL''(i,k)

and note only values equal to or greater than 1.5.
    (i) Step 9: For each of the relevant one-third octave bands (3 
through 24), determine tone correction factors from the sound 
pressure level differences F (i, k) and Table A36-2.

[[Page 45219]]

[GRAPHIC] [TIFF OMITTED] TR08JY02.003

    (j) Step 10: Designate the largest of the tone correction 
factors, determined in Step 9, as C(k). (An example of the tone 
correction procedure is given in the current advisory circular for 
this part). Tone-corrected perceived noise levels PNLT(k) must be 
determined by adding the C(k) value to corresponding PNL(k) values, 
that is:

PNLT(k)=PNL(k)+C(k)

For any i-th one-third octave band, at any k-th increment of time, 
for which the tone correction factor is suspected to result from 
something other than (or in addition to) an actual tone (or any 
spectral irregularity other than airplane noise), an additional 
analysis may be made using a filter with a bandwidth narrower than 
one-third of an octave. If the narrow band analysis corroborates 
these suspicions, then a revised value for the background sound 
pressure level SPL''(i,k), may be determined from the narrow band 
analysis and used to compute a revised tone correction factor for 
that particular one-third octave band. Other methods of rejecting 
spurious tone corrections may be approved.
    A36.4.3.2  The tone correction procedure will underestimate EPNL 
if an important tone is of a frequency such that it is recorded in 
two adjacent one-third octave bands. An applicant must demonstrate 
that either:
    (a) No important tones are recorded in two adjacent one-third 
octave bands; or
    (b) That if an important tone has occurred, the tone correction 
has been adjusted to the value it would have had if the tone had 
been recorded fully in a single one-third octave band.
    A36.4.4  Maximum tone-corrected perceived noise level
    A36.4.4.1  The maximum tone-corrected perceived noise level, 
PNLTM, must be the maximum calculated value of the tone-corrected 
perceived noise level PNLT(k). It must be calculated using the 
procedure of section A36.4.3. To obtain a satisfactory noise time 
history, measurements must be made at 0.5 second time intervals.

    Note 1: Figure A36-2 is an example of a flyover noise time 
history where the maximum value is clearly indicated.


    Note 2: In the absence of a tone correction factor, PNLTM would 
equal PNLM.


[[Page 45220]]


[GRAPHIC] [TIFF OMITTED] TR08JY02.004

    A36.4.4.2  After the value of PNLTM is obtained, the frequency 
band for the largest tone correction factor is identified for the 
two preceding and two succeeding 500 ms data samples. This is 
performed in order to identity the possibility of tone suppression 
at PNLTM by one-third octave band sharing of that tone. If the value 
of the tone correction factor C(k) for PNLTM is less than the 
average value of C(k) for the five consecutive time intervals, the 
average value of C(k) must be used to compute a new value for PNLTM.
    A36.4.5  Duration correction.
    A36.4.5.1  The duration correction factor D determined by the 
integration technique is defined by the expression:
[GRAPHIC] [TIFF OMITTED] TR08JY02.005

where T is a normalizing time constant, PNLTM is the maximum value 
of PNLT, t(1) is the first point of time after which PNLT becomes 
greater than PNLTM-10, and t(2) is the point of time after which 
PNLT remains constantly less than PNLTM-10.
    A36.4.5.2  Since PNLT is calculated from measured values of 
sound pressure level (SPL), there is no obvious equation for PNLT as 
a function of time. Consequently, the equation is to be rewritten 
with a summation sign instead of an integral sign as follows:
[GRAPHIC] [TIFF OMITTED] TR08JY02.006

where [Delta]t is the length of the equal increments of time for 
which PNLT(k) is calculated and d is the time interval to the 
nearest 0.5s during which PNLT(k) remains greater or equal to PNLTM-
10.
    A36.4.5.3  To obtain a satisfactory history of the perceived 
noise level use one of the following:
    (a) Half-Second time intervals for [Delta]t; or
    (b) A shorter time interval with approved limits and constants.
    A36.4.5.4  The following values for T and [Delta]t must be used 
in calculating D in the equation given in section A36.4.5.2:

T = 10 s, and
[Delta]t = 0.5s (or the approved sampling time interval).

Using these values, the equation for D becomes:
[GRAPHIC] [TIFF OMITTED] TR08JY02.007


[[Page 45221]]


where d is the duration time defined by the points corresponding to 
the values PNLTM-10.
    A36.4.5.5  If in using the procedures given in section 
A36.4.5.2, the limits of PNLTM-10 fall between the calculated 
PNLT(k) values (the usual case), the PNLT(k) values defining the 
limits of the duration interval must be chosen from the PNLT(k) 
values closest to PNLTM-10. For those cases with more than one peak 
value of PNLT(k), the applicable limits must be chosen to yield the 
largest possible value for the duration time.
    A36.4.6  Effective perceived noise level.
    The total subjective effect of an airplane noise event, 
designated effective perceived noise level, EPNL, is equal to the 
algebraic sum of the maximum value of the tone-corrected perceived 
noise level, PNLTM, and the duration correction D. That is:

EPNL = PNLTM + D

where PNLTM and D are calculated using the procedures given in 
sections A36.4.2, A36.4.3, A36.4.4. and A36.4.5.
    A36.4.7  Mathematical formulation of noy tables.
    A36.4.7.1  The relationship between sound pressure level (SPL) 
and the logarithm of perceived noisiness is illustrated in Figure 
A36-3 and Table A36-3.
    A36.4.7.2  The bases of the mathematical formulation are:
    (a) The slopes (M(b), M(c), M(d) and M(e)) of the straight 
lines;
    (b) The intercepts (SPL(b) and SPL(c)) of the lines on the SPL 
axis; and
    (c) The coordinates of the discontinuities, SPL(a) and log n(a); 
SPL(d) and log n = -1.0; and SPL(e) and log n = log (0.3).
    A36.4.7.3  Calculate noy values using the following equations:
    (a)

SPL [ge] SPL (a)
n = antilog {M(c)[SPL - SPL(c)]{time} 

    (b)

SPL(b) [le] SPL < SPL(a)
n = antilog {M(b)[SPL - SPL(b)]{time} 

    (c)

SPL(e) [le] SPL < SPL(b)
n = 0.3 antilog {M(e)[SPL - SPL(e)]{time} 

    (d)

SPL(d) [le] SPL < SPL(e)
n = 0.1 antilog {M(d)[SPL - SPL(d)]{time} 

    A36.4.7.4  Table A36-3 lists the values of the constants 
necessary to calculate perceived noisiness as a function of sound 
pressure level.
[GRAPHIC] [TIFF OMITTED] TR08JY02.008


[[Page 45222]]


[GRAPHIC] [TIFF OMITTED] TR08JY02.009

Section A36.5  Reporting of Data to the FAA

    A36.5.1  General.
    A36.5.1.1  Data representing physical measurements and data used 
to make corrections to physical measurements must be recorded in an 
approved permanent form and appended to the record.
    A36.5.1.2  All corrections must be reported to and approved by 
the FAA, including corrections to measurements for equipment 
response deviations.
    A36.5.1.3  Applicants may be required to submit estimates of the 
individual errors inherent in each of the operations employed in 
obtaining the final data.
    A36.5.2  Data reporting.
    An applicant is required to submit a noise certification 
compliance report that includes the following.
    A36.5.2.1  The applicant must present measured and corrected 
sound pressure levels in one-third octave band levels that are 
obtained with equipment conforming to the standards described in 
section A36.3 of this appendix.
    A36.5.2.2  The applicant must report the make and model of 
equipment used for measurement and analysis of all acoustic 
performance and meteorological data.
    A36.5.2.3  The applicant must report the following atmospheric 
environmental data, as measured immediately before, after, or during 
each test at the observation points prescribed in section A36.2 of 
this appendix.
    (a) Air temperature and relative humidity;
    (b) Maximum, minimum and average wind velocities; and
    (c) Atmospheric pressure.
    A36.5.2.4  The applicant must report conditions of local 
topography, ground cover, and events that might interfere with sound 
recordings.
    A36.5.2.5  The applicant must report the following:
    (a) Type, model and serial numbers (if any) of airplane, 
engine(s), or propeller(s) (as applicable);
    (b) Gross dimensions of airplane and location of engines;
    (c) Airplane gross weight for each test run and center of 
gravity range for each series of test runs;
    (d) Airplane configuration such as flap, airbrakes and landing 
gear positions for each test run;
    (e) Whether auxiliary power units (APU), when fitted, are 
operating for each test run;

[[Page 45223]]

    (f) Status of pneumatic engine bleeds and engine power take-offs 
for each test run;
    (g) Indicated airspeed in knots or kilometers per hour for each 
test run;
    (h) Engine performance data:
    (1) For jet airplanes: engine performance in terms of net 
thrust, engine pressure ratios, jet exhaust temperatures and fan or 
compressor shaft rotational speeds as determined from airplane 
instruments and manufacturer's data for each test run;
    (2) For propeller-driven airplanes: engine performance in terms 
of brake horsepower and residual thrust; or equivalent shaft 
horsepower; or engine torque and propeller rotational speed; as 
determined from airplane instruments and manufacturer's data for 
each test run;
    (i) Airplane flight path and ground speed during each test run; 
and
    (j) The applicant must report whether the airplane has any 
modifications or non-standard equipment likely to affect the noise 
characteristics of the airplane. The FAA must approve any such 
modifications or non-standard equipment.
    A36.5.3  Reporting of noise certification reference conditions.
    A36.5.3.1  Airplane position and performance data and the noise 
measurements must be corrected to the noise certification reference 
conditions specified in the relevant sections of appendix B of this 
part. The applicant must report these conditions, including 
reference parameters, procedures and configurations.
    A36.5.4  Validity of results.
    A36.5.4.1  Three average reference EPNL values and their 90 
percent confidence limits must be produced from the test results and 
reported, each such value being the arithmetical average of the 
adjusted acoustical measurements for all valid test runs at each 
measurement point (flyover, lateral, or approach). If more than one 
acoustic measurement system is used at any single measurement 
location, the resulting data for each test run must be averaged as a 
single measurement. The calculation must be performed by:
    (a) Computing the arithmetic average for each flight phase using 
the values from each microphone point; and
    (b) Computing the overall arithmetic average for each reference 
condition (flyover, lateral or approach) using the values in 
paragraph (a) of this section and the related 90 percent confidence 
limits.
    A36.5.4.2  For each of the three certification measuring points, 
the minimum sample size is six. The sample size must be large enough 
to establish statistically for each of the three average noise 
certification levels a 90 percent confidence limit not exceeding 
1.5 EPNdB. No test result may be omitted from the 
averaging process unless approved by the FAA.

    Note: Permitted methods for calculating the 90 percent 
confidence interval are shown in the current advisory circular for 
this part.

    A36.5.4.3  The average EPNL figures obtained by the process 
described in section A36.5.4.1 must be those by which the noise 
performance of the airplane is assessed against the noise 
certification criteria.

             Section A36.6  Nomenclature: Symbols and Units
------------------------------------------------------------------------
            Symbol                     Unit               Meaning
------------------------------------------------------------------------
antilog.......................  .................  Antilogarithm to the
                                                    base 10.
C(k)..........................  dB...............  Tone correction
                                                    factor. The factor
                                                    to be added to
                                                    PNL(k) to account
                                                    for the presence of
                                                    spectral
                                                    irregularities such
                                                    as tones at the k-th
                                                    increment of time.
d.............................  s................  Duration time. The
                                                    time interval
                                                    between the limits
                                                    of t(1) and t(2) to
                                                    the nearest 0.5
                                                    second.
D.............................  dB...............  Duration correction.
                                                    The factor to be
                                                    added to PNLTM to
                                                    account for the
                                                    duration of the
                                                    noise.
EPNL..........................  EPNdB............  Effective perceived
                                                    noise level. The
                                                    value of PNL
                                                    adjusted for both
                                                    spectral
                                                    irregularities and
                                                    duration of the
                                                    noise. (The unit
                                                    EPNdB is used
                                                    instead of the unit
                                                    dB).
EPNLr.........................  EPNdB............  Effective perceived
                                                    noise level adjusted
                                                    for reference
                                                    conditions.
f(i)..........................  Hz...............  Frequency. The
                                                    geometrical mean
                                                    frequency for the i-
                                                    th one-third octave
                                                    band.
F (i, k)......................  dB...............  Delta-dB. The
                                                    difference between
                                                    the original sound
                                                    pressure level and
                                                    the final background
                                                    sound pressure level
                                                    in the i-th one-
                                                    third octave band at
                                                    the k-th interval of
                                                    time. In this case,
                                                    background sound
                                                    pressure level means
                                                    the broadband noise
                                                    level that would be
                                                    present in the one-
                                                    third octave band in
                                                    the absence of the
                                                    tone.
h.............................  dB...............  dB-down. The value to
                                                    be subtracted from
                                                    PNLTM that defines
                                                    the duration of the
                                                    noise.
H.............................  Percent..........  Relative humidity.
                                                    The ambient
                                                    atmospheric relative
                                                    humidity.
i.............................  .................  Frequency band index.
                                                    The numerical
                                                    indicator that
                                                    denotes any one of
                                                    the 24 one-third
                                                    octave bands with
                                                    geometrical mean
                                                    frequencies from 50
                                                    to 10,000 Hz.
k.............................  .................  Time increment index.
                                                    The numerical
                                                    indicator that
                                                    denotes the number
                                                    of equal time
                                                    increments that have
                                                    elapsed from a
                                                    reference zero.
Log...........................  .................  Logarithm to the base
                                                    10.
log n(a)......................  .................  Noy discontinuity
                                                    coordinate. The log
                                                    n value of the
                                                    intersection point
                                                    of the straight
                                                    lines representing
                                                    the variation of SPL
                                                    with log n.
M(b), M(c), etc...............  .................  Noy inverse slope.
                                                    The reciprocals of
                                                    the slopes of
                                                    straight lines
                                                    representing the
                                                    variation of SPL
                                                    with log n.
n.............................  noy..............  The perceived
                                                    noisiness at the k-
                                                    th instant of time
                                                    that occurs in the i-
                                                    th one-third octave
                                                    band.
n(k)..........................  noy..............  Maximum perceived
                                                    noisiness. The
                                                    maximum value of all
                                                    of the 24 values of
                                                    n(i) that occurs at
                                                    the k-th instant of
                                                    time.
N(k)..........................  noy..............  Total perceived
                                                    noisiness. The total
                                                    perceived noisiness
                                                    at the k-th instant
                                                    of time calculated
                                                    from the 24-
                                                    instantaneous values
                                                    of n (i, k).
p(b), p(c), etc...............  .................  Noy slope. The slopes
                                                    of straight lines
                                                    representing the
                                                    variation of SPL
                                                    with log n.
PNL...........................  PNdB.............  The perceived noise
                                                    level at any instant
                                                    of time. (The unit
                                                    PNdB is used instead
                                                    of the unit dB).

[[Page 45224]]

 
PNL(k)........................  PNdB.............  The perceived noise
                                                    level calculated
                                                    from the 24 values
                                                    of SPL (i, k), at
                                                    the k-th increment
                                                    of time. (The unit
                                                    PNdB is used instead
                                                    of the unit dB).
PNLM..........................  PNdB.............  Maximum perceived
                                                    noise level. The
                                                    maximum value of
                                                    PNL(k). (The unit
                                                    PNdB is used instead
                                                    of the unit dB).
PNLT..........................  TPNdB............  Tone-corrected
                                                    perceived noise
                                                    level. The value of
                                                    PNL adjusted for the
                                                    spectral
                                                    irregularities that
                                                    occur at any instant
                                                    of time. (The unit
                                                    TPNdB is used
                                                    instead of the unit
                                                    dB).
PNLT(k).......................  TPNdB............  The tone-corrected
                                                    perceived noise
                                                    level that occurs at
                                                    the k-th increment
                                                    of time. PNLT(k) for
                                                    the spectral
                                                    irregularities that
                                                    occur at the k-th
                                                    increment of time.
                                                    (The unit TPNdB is
                                                    used instead of the
                                                    unit dB).
PNLTM.........................  TPNdB............  Maximum tone-
                                                    corrected perceived
                                                    noise level. The
                                                    maximum value of
                                                    PNLT(k). (The unit
                                                    TPNdB is used
                                                    instead of the unit
                                                    dB).
PNLTr.........................  TPNdB............  Tone-corrected
                                                    perceived noise
                                                    level adjusted for
                                                    reference
                                                    conditions.
s (i, k)......................  dB...............  Slope of sound
                                                    pressure level. The
                                                    change in level
                                                    between adjacent one-
                                                    third octave band
                                                    sound pressure
                                                    levels at the i-th
                                                    band for the k-th
                                                    instant of time.
[Delta]s (i, k)...............  dB...............  Change in slope of
                                                    sound pressure
                                                    level.
s' (i, k).....................  dB...............  Adjusted slope of
                                                    sound pressure
                                                    level. The change in
                                                    level between
                                                    adjacent adjusted
                                                    one-third octave
                                                    band sound pressure
                                                    levels at the i-th
                                                    band for the k-th
                                                    instant of time.
s (i, k)......................  dB...............  Average slope of
                                                    sound pressure
                                                    level.
SPL...........................  dB re............  Sound pressure level.
                                20 [mu]Pa........   The sound pressure
                                                    level that occurs in
                                                    a specified
                                                    frequency range at
                                                    any instant of time.
SPL(a)........................  dB re............  Noy discontinuity
                                20 [mu]Pa........   coordinate. The SPL
                                                    value of the
                                                    intersection point
                                                    of the straight
                                                    lines representing
                                                    the variation of SPL
                                                    with log n.
SPL(b)........................  dB re............  Noy intercept. The
SPL (c).......................  20 [mu]Pa........   intercepts on the
                                                    SPL-axis of the
                                                    straight lines
                                                    representing the
                                                    variation of SPL
                                                    with log n.
SPL (i, k)....................  dB re............  The sound pressure
                                20 [mu]Pa........   level at the k-th
                                                    instant of time that
                                                    occurs in the i-th
                                                    one-third octave
                                                    band.
SPL' (i, k)...................  dB re............  Adjusted sound
                                20 [mu]Pa........   pressure level. The
                                                    first approximation
                                                    to background sound
                                                    pressure level in
                                                    the i-th one-third
                                                    octave band for the
                                                    k-th instant of
                                                    time.
SPL(i)........................  dB re............  Maximum sound
                                20 [mu]Pa........   pressure level. The
                                                    sound pressure level
                                                    that occurs in the i-
                                                    th one-third octave
                                                    band of the spectrum
                                                    for PNLTM.
SPL(i)r.......................  dB re............  Corrected maximum
                                20 [mu]Pa........   sound pressure
                                                    level. The sound
                                                    pressure level that
                                                    occurs in the i-th
                                                    one-third octave
                                                    band of the spectrum
                                                    for PNLTM corrected
                                                    for atmospheric
                                                    sound absorption.
SPL'' (i, k)..................  dB re............  Final background
                                20 [mu]Pa........   sound pressure
                                                    level. The second
                                                    and final
                                                    approximation to
                                                    background sound
                                                    pressure level in
                                                    the i-th one-third
                                                    octave band for the
                                                    k-th instant of
                                                    time.
t.............................  s................  Elapsed time. The
                                                    length of time
                                                    measured from a
                                                    reference zero.
t(1), t(2)....................  s................  Time limit. The
                                                    beginning and end,
                                                    respectively, of the
                                                    noise time history
                                                    defined by h.
[Delta]t......................  s................  Time increment. The
                                                    equal increments of
                                                    time for which
                                                    PNL(k) and PNLT(k)
                                                    are calculated.
T.............................  s................  Normalizing time
                                                    constant. The length
                                                    of time used as a
                                                    reference in the
                                                    integration method
                                                    for computing
                                                    duration
                                                    corrections, where
                                                    T=10s.
t( deg.F) ( deg.C)............   deg.F,  deg.C...  Temperature. The
                                                    ambient air
                                                    temperature.
[alpha](i)....................  dB/1000ft db/100m  Reference atmospheric
                                                    absorption. The
                                                    atmospheric
                                                    attenuation of sound
                                                    that occurs in the i-
                                                    th one-third octave
                                                    band at the measured
                                                    air temperature and
                                                    relative humidity.
[alpha](i)o...................  dB/1000ft db/100m  Reference atmospheric
                                                    absorption. The
                                                    atmospheric
                                                    attenuation of
                                                    sound.
A1............................  Degrees..........  First constant climb
                                                    angle (Gear up,
                                                    speed of at least
                                                    V2+10 kt (V2+19 km/
                                                    h), takeoff thrust).
A2............................  Degrees..........  Second constant climb
                                                    angle (Gear up,
                                                    speed of at least
                                                    V2+10 kt (V2+19 km/
                                                    h), after cut-back).
[delta].......................  Degrees..........  Thrust cutback
[egr].........................                      angles. The angles
                                                    defining the points
                                                    on the takeoff
                                                    flight path at which
                                                    thrust reduction is
                                                    started and ended
                                                    respectively.
[eta].........................  Degrees..........  Approach angle.
[eta]r........................  Degrees..........  Reference approach
                                                    angle.
[thetas]......................  Degrees..........  Noise angle (relative
                                                    to flight path). The
                                                    angle between the
                                                    flight path and
                                                    noise path. It is
                                                    identical for both
                                                    measured and
                                                    corrected flight
                                                    paths.
[psi].........................  Degrees..........  Noise angle (relative
                                                    to ground). The
                                                    angle between the
                                                    noise path and the
                                                    ground. It is
                                                    identical for both
                                                    measured and
                                                    corrected flight
                                                    paths.

[[Page 45225]]

 
[mu]..........................  .................  Engine noise emission
                                                    parameter.
[mu]r.........................  .................  Reference engine
                                                    noise emission
                                                    parameter.
[Delta]1......................  EPNdB............  PNLT correction. The
                                                    correction to be
                                                    added to the EPNL
                                                    calculated from
                                                    measured data to
                                                    account for noise
                                                    level changes due to
                                                    differences in
                                                    atmospheric
                                                    absorption and noise
                                                    path length between
                                                    reference and test
                                                    conditions.
[Delta]2......................  EPNdB............  Adjustment to
                                                    duration correction.
                                                    The adjustment to be
                                                    made to the EPNL
                                                    calculated from
                                                    measured data to
                                                    account for noise
                                                    level changes due to
                                                    the noise duration
                                                    between reference
                                                    and test conditions.
[Delta]3......................  EPNdB............  Source noise
                                                    adjustment. The
                                                    adjustment to be
                                                    made to the EPNL
                                                    calculated from
                                                    measured data to
                                                    account for noise
                                                    level changes due to
                                                    differences between
                                                    reference and test
                                                    engine operating
                                                    conditions.
------------------------------------------------------------------------

Section A36.7  Sound Attenuation in Air

    A36.7.1  The atmospheric attenuation of sound must be determined 
in accordance with the procedure presented in section A36.7.2.
    A36.7.2  The relationship between sound attenuation, frequency, 
temperature, and humidity is expressed by the following equations.
    A36.7.2(a)  For calculations using the English System of Units:
    [GRAPHIC] [TIFF OMITTED] TR08JY02.010
    
and
[GRAPHIC] [TIFF OMITTED] TR08JY02.011

where

[eta]([delta]) is listed in Table A36-4 and f0 in Table 
A36-5;
[alpha](i) is the attenuation coefficient in dB/1000 ft;
[thetas] is the temperature in  deg.F; and
H is the relative humidity, expressed as a percentage.

    A36.7.2(b) For calculations using the International System of 
Units (SI):
[GRAPHIC] [TIFF OMITTED] TR08JY02.012

and
[GRAPHIC] [TIFF OMITTED] TR08JY02.013

where

[eta]([delta]) is listed in Table A36-4 and f0 in Table 
A36-5;
[alpha](i) is the attenuation coefficient in dB/100 m;
[thetas] is the temperature in  deg.C; and
H is the relative humidity, expressed as a percentage.

    A36.7.3  The values listed in table A36-4 are to be used when 
calculating the equations listed in section A36.7.2. A term of 
quadratic interpolation is to be used where necessary.

Section A36.8  [Reserved]

[[Page 45226]]

[GRAPHIC] [TIFF OMITTED] TR08JY02.014

Section A36.9  Adjustment of airplane flight test results.

    A36.9.1  When certification test conditions are not identical to 
reference conditions, appropriate adjustments must be made to the 
measured noise data using the methods described in this section.
    A36.9.1.1  Adjustments to the measured noise values must be made 
using one of the methods described in sections A36.9.3 and A36.9.4 
for differences in the following:
    (a) Attenuation of the noise along its path as affected by 
``inverse square'' and atmospheric attenuation
    (b) Duration of the noise as affected by the distance and the 
speed of the airplane relative to the measuring point
    (c) Source noise emitted by the engine as affected by the 
differences between test and reference engine operating conditions
    (d) Airplane/engine source noise as affected by differences 
between test and reference airspeeds. In addition to the effect on 
duration, the effects of airspeed on component noise sources must be 
accounted for as follows: for conventional airplane configurations, 
when differences between test and reference airspeeds exceed 15 
knots (28 km/h) true airspeed, test data and/or analysis approved by 
the FAA must be used to qualify the effects of the airspeed 
adjustment on resulting certification noise levels.
    A36.9.1.2  The ``integrated'' method of adjustment, described in 
section A36.9.4, must be used on takeoff or approach under the 
following conditions:

[[Page 45227]]

    (a) When the amount of the adjustment (using the ``simplified'' 
method) is greater than 8 dB on flyover, or 4 dB on approach; or
    (b) When the resulting final EPNL value on flyover or approach 
(using the simplified method) is within 1 dB of the limiting noise 
levels as prescribed in section B36.5 of this part.
    A36.9.2  Flight profiles.
    As described below, flight profiles for both test and reference 
conditions are defined by their geometry relative to the ground, 
together with the associated airplane speed relative to the ground, 
and the associated engine control parameter(s) used for determining 
the noise emission of the airplane.
    A36.9.2.1  Takeoff Profile.

    Note: Figure A36-4 illustrates a typical takeoff profile.

    (a) The airplane begins the takeoff roll at point A, lifts off 
at point B and begins its first climb at a constant angle at point 
C. Where thrust or power (as appropriate) cut-back is used, it is 
started at point D and completed at point E. From here, the airplane 
begins a second climb at a constant angle up to point F, the end of 
the noise certification takeoff flight path.
    (b) Position K1 is the takeoff noise measuring 
station and AK1 is the distance from start of roll to the 
flyover measuring point. Position K2 is the lateral noise 
measuring station, which is located on a line parallel to, and the 
specified distance from, the runway center line where the noise 
level during takeoff is greatest.
    (c) The distance AF is the distance over which the airplane 
position is measured and synchronized with the noise measurements, 
as required by section A36.2.3.2 of this part.
    A36.9.2.2  Approach Profile.

    Note: Figure A36-5 illustrates a typical approach profile.

    (a) The airplane begins its noise certification approach flight 
path at point G and touches down on the runway at point J, at a 
distance OJ from the runway threshold.
    (b) Position K3 is the approach noise measuring 
station and K3O is the distance from the approach noise 
measurement point to the runway threshold.
    (c) The distance GI is the distance over which the airplane 
position is measured and synchronized with the noise measurements, 
as required by section A36.2.3.2 of this part.

[[Page 45228]]

[GRAPHIC] [TIFF OMITTED] TR08JY02.015

The airplane reference point for approach measurements is the 
instrument landing system (ILS) antenna. If no ILS antenna is 
installed an alternative reference point must be approved by the 
FAA.
    A36.9.3  Simplified method of adjustment.
    A36.9.3.1  General. As described below, the simplified 
adjustment method consists of applying adjustments (to the EPNL, 
which is calculated from the measured data) for the differences 
between measured and reference conditions at the moment of PNLTM.
    A36.9.3.2  Adjustments to PNL and PNLT.
    (a) The portion of the test flight path and the reference flight 
path described below, and illustrated in Figure A36-6, include the

[[Page 45229]]

noise time history that is relevant to the calculation of flyover 
and approach EPNL. In figure A36-6:
    (1) XY represents the portion of the measured flight path that 
includes the noise time history relevant to the calculation of 
flyover and approach EPNL; XrYr represents the 
corresponding portion of the reference flight path.
    (2) Q represents the airplane's position on the measured flight 
path at which the noise was emitted and observed as PNLTM at the 
noise measuring station K. Qr is the corresponding 
position on the reference flight path, and Kr the 
reference measuring station. QK and QrKr are, 
respectively, the measured
[GRAPHIC] [TIFF OMITTED] TR08JY02.016

and reference noise propagation paths, Qr being 
determined from the assumption that QK and 
QrKr form the same angle with their respective 
flight paths.
    (b) The portions of the test flight path and the reference 
flight path described in paragraph (b)(1) and (2), and illustrated 
in Figure A36-7(a) and (b), include the noise time history that is 
relevant to the calculation of lateral EPNL.
    (1) In figure A36-7(a), XY represents the portion of the 
measured flight path that includes the noise time history that is 
relevant to the calculation of lateral EPNL; in figure AQ36-7(b), 
XrYr represents the corresponding portion of 
the reference flight path.
    (2) Q represents the airplane position on the measured flight 
path at which the noise was emitted and observed as PNLTM at the 
noise measuring station K. Qr is the corresponding 
position on the reference flight path, and Kr the 
reference measuring station. QK and QrKr are, 
respectively, the measured and reference noise propagation paths. In 
this case Kr is only specified as being on a particular 
Lateral line; Kr and Qr are therefore 
determined from the assumption that QK and 
QrKr:
    (i) Form the same angle [thetas] with their respective flight 
paths; and
    (ii) Form the same angle [psi] with the ground.

    Note: For the lateral noise measurement, sound propagation is 
affected not only by inverse square and atmospheric attenuation, but 
also by ground absorption and reflection effects which depend mainly 
on the angle [psi].


[[Page 45230]]


[GRAPHIC] [TIFF OMITTED] TR08JY02.017

    A36.9.3.2.1  The one-third octave band levels SPL(i) comprising 
PNL (the PNL at the moment of PNLTM observed at K) must be adjusted 
to reference levels SPL(i)r as follows:
    A36.9.3.2.1(a)  For calculations using the English System of 
Units:

SPL(i)r=SPL(i)+0.001[[alpha](i)-[alpha](i)0]QK
+0.0001[alpha](i)0(QK-QrKr)
+20log(QK/QrKr)

    In this expression,
    (1) The term 0.001[[alpha](i)-[alpha](i)0]QK is the 
adjustment for the effect of the change in sound attenuation 
coefficient, and [alpha](i) and [alpha](i)0 are the 
coefficients for the test and reference atmosphere conditions 
respectively, determined under section A36.7 of this appendix;
    (2) The term 0.001[alpha](i)0(QK - 
QrKr) is the adjustment for the effect of the 
change in the noise path length on the sound attenuation;
    (3) The term 20 log(QK/QrKr) is the 
adjustment for the effect of the change in the noise path length due 
to the ``inverse square'' law;
    (4) QK and QrKr are measured in feet and 
[alpha](i) and [alpha](i)0 are expressed in dB/1000 ft.
    A36.9.3.2.1(b) For calculations using the International System 
of Units:

SPL(i)r = SPL(i) + 0.01[[alpha](i) - 
[alpha](i)0]QK
+ 0.01[alpha](i)0 (QK - QrKr)
+ 20 log(QK/QrKr)

In this expression,
    (1) The term 0.01[[alpha](i) - [alpha](i)0]QK is the 
adjustment for the effect of the change in sound attenuation 
coefficient, and [alpha](i) and [alpha](i)0 are the 
coefficients for the test and reference atmospheric conditions 
respectively, determined under section A36.7 of this appendix;
    (2) The term 0.01[alpha](i)0(QK - 
QrKr) is the adjustment for the effect of the 
change in the noise path length on the sound attenuation;
    (3) The term 20 log(QK/QrKr) is the 
adjustment for the effect of the change in the noise path length due 
to the inverse square law;
    (4) QK and QrKr are measured in meters and 
[alpha](i) and [alpha](i)0 are expressed in dB/100 m.
    A36.9.3.2.1.1 PNLT Correction.
    (a) Convert the corrected values, SPL(i)r, to 
PNLTr;
    (b) Calculate the correction term [Delta]1 using the 
following equation:

[Delta]1 = PNTr - PNLTM

    A36.9.3.2.1.2  Add [Delta]1 arithmetically to the 
EPNL calculated from the measured data.
    A36.9.3.2.2  If, during a test flight, several peak values of 
PNLT that are within 2 dB of PNLTM are observed, the procedure 
defined in section A36.9.3.2.1 must be applied at each peak, and the 
adjustment term, calculated according to section A36.9.3.2.1, must 
be added to each peak to give corresponding adjusted peak values of 
PNLT. If these peak values exceed the value at the moment of PNLTM, 
the maximum value of such exceedance must be added as a further 
adjustment to the EPNL calculated from the measured data.
    A36.9.3.3  Adjustments to duration correction.
    A36.9.3.3.1  Whenever the measured flight paths and/or the 
ground velocities of the test conditions differ from the reference 
flight paths and/or the ground velocities of the reference 
conditions, duration adjustments must be applied to the EPNL values 
calculated from the measured data. The adjustments must be 
calculated as described below.

[[Page 45231]]

    A36.9.3.3.2  For the flight path shown in Figure A36-6, the 
adjustment term is calculated as follows:

[Delta]2 = -7.5 log(QK/QrKr) + 10 
log(V/Vr)

    (a) Add [Delta]2 arithmetically to the EPNL 
calculated from the measured data.
    A36.9.3.4  Source noise adjustments.
    A36.9.3.4.1  To account for differences between the parameters 
affecting engine noise as measured in the certification flight 
tests, and those calculated or specified in the reference 
conditions, the source noise adjustment must be calculated and 
applied. The adjustment is determined from the manufacturer's data 
approved by the FAA. Typical data used for this adjustment are 
illustrated in Figure A36-8 that shows a curve of EPNL versus the 
engine control parameter [mu], with the EPNL data being corrected to 
all the other relevant reference conditions (airplane mass, speed 
and altitude, air temperature) and for the difference in noise 
between the test engine and the average engine (as defined in 
section B36.7(b)(7)). A sufficient number of data points over a 
range of values of [mu]r is required to calculate the 
source noise adjustments for lateral, flyover and approach noise 
measurements.
[GRAPHIC] [TIFF OMITTED] TR08JY02.018

    A36.9.3.4.2  Calculate adjustment term [Delta]3 by 
subtracting the EPNL value corresponding to the parameter [mu] from 
the EPNL value corresponding to the parameter [mu]r. Add 
[Delta]3 arithmetically to the EPNL value calculated from 
the measured data.
    A36.9.3.5  Symmetry adjustments.
    A36.9.3.5.1  A symmetry adjustment to each lateral noise value 
(determined at the section B36.4(b) measurement points), is to be 
made as follows:
    (a) If the symmetrical measurement point is opposite the point 
where the highest noise level is obtained on the main lateral 
measurement line, the certification noise level is the arithmetic 
mean of the noise levels measured at these two points (see Figure 
A36-9(a));
    (b) If the condition described in paragraph (a) of this section 
is not met, then it is assumed that the variation of noise with the 
altitude of the airplane is the same on both sides, there is a 
constant difference between the lines of noise versus altitude on 
both sides (see figure A36-9(b)). The certification noise level is 
the maximum value of the mean between these lines.
[GRAPHIC] [TIFF OMITTED] TR08JY02.019

    A36.9.4  Integrated method of adjustment
    A36.9.4.1  General. As described in this section, the integrated 
adjustment method consists of recomputing under reference conditions 
points on the PNLT time history corresponding to measured points 
obtained during the tests, and computing EPNL directly for the new 
time history obtained in this way. The main principles are described 
in sections A36.9.4.2 through A36.9.4.4.1.
    A36.9.4.2  PNLT computations.
    (a) The portions of the test flight path and the reference 
flight path described in paragraph (a)(1) and (2), and illustrated 
in Figure A36-10, include the noise time history that is relevant to 
the calculation of flyover and approach EPNL. In figure A36-10:

[[Page 45232]]

[GRAPHIC] [TIFF OMITTED] TR08JY02.020

    (1) XY represents the portion of the measured flight path that 
includes the noise time history relevant to the calculation of 
flyover and approach EPNL; XrYr represents the 
corresponding reference flight path.
    (2) The points Q0, Q1, Qn 
represent airplane positions on the measured flight path at time 
t0, t1 and tn respectively. Point 
Q1 is the point at which the noise was emitted and 
observed as one-third octave values SPL(i)1 at the noise 
measuring station K at a time t1. Point Qr1 
represents the corresponding position on the reference flight path 
for noise observed as SPL(i)r1 at the reference measuring 
station Kr at time tr1. Q1K and 
Qr1Kr are respectively the measured and 
reference noise propagation paths, which in each case form the angle 
[thetas]1 with their respective flight paths. 
Qr0 and Qrn are similarly the points on the 
reference flight path corresponding to Q0 and 
Qn on the measured flight path. Q0 and 
Qn are chosen so that between Qr0 and 
Qrn all values of PNLTr (computed as described 
in paragraphs A36.9.4.2.2 and A36.9.4.2.3) within 10 dB of the peak 
value are included.
    (b) The portions of the test flight path and the reference 
flight path described in paragraph (b)(1) and (2), and illustrated 
in Figure A36-11(a) and (b), include the noise time history that is 
relevant to the calculation of lateral EPNL.
    (1) In figure A36-11(a) XY represents the portion of the 
measured flight path that includes the noise time history that is 
relevant to the calculation of lateral EPNL; in figure A36-11(b), 
XrYr represents the corresponding portion of 
the reference flight path.
    (2) The points Q0, Q1 and Qn 
represent airplane positions on the measured flight path at time 
t0, t1 and tn respectively. Point 
Q1 is the point at which the noise was emitted and 
observed as one-third octave values SPL(i)1 at the noise 
measuring station K at time t1. The point Qr1 
represents the corresponding position on the reference flight path 
for noise observed as SPL(i)r1 at the measuring station 
Kr at time tr1. Q1K and 
Qr1Kr are respectively the measured and 
reference noise propagation paths Qr0 and Qrn 
are similarly the points on the reference flight path corresponding 
to Q0 and Qn on the measured flight path.

[[Page 45233]]

[GRAPHIC] [TIFF OMITTED] TR08JY02.021

    Q0 and Qn are chosen to that between 
Qro and Qrn all values of PNLTr 
computed as described in paragraphs A36.9.4.2.2 and A36.9.4.2.3) 
within 10 dB of the peak value are included. In this case 
Kr is only specified as being on a particular lateral 
line. The

[[Page 45234]]

position of Kr and Qr1 are determined from the 
following requirements.
    (i) Q1K and Qr1Kr form the same 
angle [thetas]1 with their respective flight paths; and
    (ii) The differences between the angles 
[.]1 and 
[.]r1 must be 
minimized using a method, approved by the FAA. The differences 
between the angles are minimized since, for geometrical reasons, it 
is generally not possible to choose Kr so that the 
condition described in paragraph A36.9.4.2(b)(2)(i) is met while at 
the same time keeping 
[.]1 and 
[.]r1 equal.

    Note: For the lateral noise measurement, sound propagation is 
affected not only by ``inverse square'' and atmospheric attenuation, 
but also by ground absorption and reflection effects which depend 
mainly on the angle [.].

    A36.9.4.2.1  In paragraphs A36.9.4.2(a)(2) and (b)(2) the time 
tr1 is later (for Qr1Kr  
Q1K) separate amounts:
    (1) The time taken for the airplane to travel the distance 
Qr1Qr0 at a speed Vr less the time 
taken for it to travel Q1Q0 at V;
    (2) The time taken for sound to travel the distance 
Qr1Kr-Q1K.

    Note: For the flight paths described in paragraphs A36.9.4.2(a) 
and (b), the use of thrust or power cut-back will result in test and 
reference flight paths at full thrust or power and at cut-back 
thrust or power. Where the transient region between these thrust or 
power levels affects the final result, an interpolation must be made 
between them by an approved method such as that given in the current 
advisory circular for this part.

    A36.9.4.2.2  The measured values of SPL(i)1 must be 
adjusted to the reference values SPL(i)r1 to account for 
the differences between measured and reference noise path lengths 
and between measured and reference atmospheric conditions, using the 
methods of section A36.9.3.2.1 of this appendix. A corresponding 
value of PNLr1 must be computed according to the method 
in section A36.4.2 Values of PNLr must be computed for 
times t0 through tn.
    A36.9.4.2.3  For each value of PNLr1, a tone 
correction factor C1 must be determined by analyzing the 
reference values SPL(i)r using the methods of section 
A36.4.3 of this appendix, and added to PNLr1 to yield 
PNLTr1. Using the process described in this paragraph, 
values of PNLTr must be computed for times t0 
through tn.
    A36.9.4.3  Duration correction.
    A36.9.4.3.1  The values of PNLTr corresponding to 
those of PNLT at each one-half second interval must be plotted 
against time (PNLTr1 at time tr1. The duration 
correction must then be determined using the method of section 
A36.4.5.1 of this appendix, to yield EPNLr.
    A36.9.4.4  Source Noise Adjustment.
    A36.9.4.4.1  A source noise adjustment, [Delta]3, 
must be determined using the methods of section A36.9.3.4 of this 
appendix.

              A37.9.5  Flight Path Identification Positions
------------------------------------------------------------------------
           Position                           Description
------------------------------------------------------------------------
A............................  Start of Takeoff roll.
B............................  Lift-off.
C............................  Start of first constant climb.
D............................  Start of thurst reduction.
E............................  Start of second constant climb.
F............................  End of noise certification Takeoff flight
                                path.
G............................  Start of noise certification Approach
                                flight path.
H............................  Position on Approach path directly above
                                noise measuring station.
I............................  Start of level-off.
J............................  Touchdown.
K............................  Noise measurement point.
Kr...........................  Reference measurement point.
K1...........................  Flyover noise measurement point.
K2...........................  Lateral noise measurement point.
K3...........................  Approach noise measurement point.
M............................  End of noise certification Takeoff flight
                                track.
O............................  Threshold of Approach end of runway.
P............................  Start of noise certification Approach
                                flight track.
Q............................  Position on measured Takeoff flight path
                                corresponding to apparent PNLTM at
                                station K See section A36.9.3.2.
Qr...........................  Position on corrected Takeoff flight path
                                corresponding to PNLTM at station K. See
                                section A36.9.3.2.
V............................  Airplane test speed.
Vr...........................  Airplane reference speed.
------------------------------------------------------------------------


                     A36.9.6  Flight Path Distances
------------------------------------------------------------------------
           Distance                    Unit               Meaning
------------------------------------------------------------------------
AB............................  Feet (meters)....  Length of takeoff
                                                    roll. The distance
                                                    along the runway
                                                    between the start of
                                                    takeoff roll and
                                                    lift off.
AK............................  Feet (meters)....  Takeoff measurement
                                                    distance. The
                                                    distance from the
                                                    start of roll to the
                                                    takeoff noise
                                                    measurement station
                                                    along the extended
                                                    center line of the
                                                    runway.
AM............................  Feet (meters)....  Takeoff flight track
                                                    distance. The
                                                    distance from the
                                                    start of roll to the
                                                    takeoff flight track
                                                    position along the
                                                    extended center line
                                                    of the runway after
                                                    which the position
                                                    of the airplane need
                                                    no longer be
                                                    recorded.
QK............................  Feet (meters)....  Measured noise path.
                                                    The distance from
                                                    the measured
                                                    airplane position Q
                                                    to station K.
QrKr..........................  Feet (meters)....  Reference noise path.
                                                    The distance from
                                                    the reference
                                                    airplane position Qr
                                                    to station Kr.
K3H...........................  Feet (meters)....  Airplane approach
                                                    height. The height
                                                    of the airplane
                                                    above the approach
                                                    measuring station.
OK3...........................  Feet (meters)....  Approach measurement
                                                    distance. The
                                                    distance from the
                                                    runway threshold to
                                                    the approach
                                                    measurement station
                                                    along the extended
                                                    center line of the
                                                    runway.

[[Page 45235]]

 
OP............................  Feet (meters)....  Approach flight track
                                                    distance. The
                                                    distance from the
                                                    runway threshold to
                                                    the approach flight
                                                    track position along
                                                    the extended center
                                                    line of the runway
                                                    after which the
                                                    position of the
                                                    airplane need no
                                                    longer be recorded.
------------------------------------------------------------------------


    16. Appendix B of part 36 is revised to read as follows:

Appendix B to Part 36--Noise Levels for Transport Category and Jet 
Airplanes Under Sec. 36.103

Sec.
B36.1  Noise measurement and evaluation.
B36.2  Noise evaluation metric.
B36.3  Reference noise measurement points.
B36.4  Test noise measurement points.
B36.5  Maximum noise levels.
B36.6  Trade-offs.
B36.7  Noise certification reference procedures and conditions.
B36.8  Noise certification test procedures.

Section B36.1  Noise Measurement and Evaluation

    Compliance with this appendix must be shown with noise levels 
measured and evaluated using the procedures of appendix A of this 
part, or under approved equivalent procedures.

Section B36.2  Noise Evaluation Metric

    The noise evaluation metric is the effective perceived noise 
level expressed in EPNdB, as calculated using the procedures of 
appendix A of this part.

Section B36.3  Reference Noise Measurement Points

    When tested using the procedures of this part, except as 
provided in section B36.6, an airplane may not exceed the noise 
levels specified in section B36.5 at the following points on level 
terrain:
    (a) Lateral full-power reference noise measurement point:
    (1) For jet airplanes: The point on a line parallel to an 1,476 
feet (450 m) from the runway centerline, or extended centerline, 
where the noise level after lift-off is at a maximum during takeoff. 
For the purpose of showing compliance with Stage 1 or Stage 2 noise 
limits for an airplane powered by more than three jet engines, the 
distance from the runway centerline must be 0.35 nautical miles (648 
m). For jet airplanes, when approved by the FAA, the maximum lateral 
noise at takeoff thrust may be assumed to occur at the point (or its 
approved equivalent) along the extended centerline of the runway 
where the airplane reaches 985 feet (300 meters) altitude above 
ground level. A height of 1427 feet (435 meters) may be assumed for 
State 1 or Stage 2 four engine airplanes. The altitude of the 
airplane as it passes the noise measurement points must be within 
+328 to -164 feet (+100 to -50 meters) of the target altitude. For 
airplanes powered by other than jet engines, the altitude for 
maximum lateral noise must be determined experimentally.
    (2) For propeller-driven airplanes: The point on the extended 
centerline of the runway above which the airplane, at full takeoff 
power, reaches a height of 2,133 feet (650 meters). For tests 
conducted before [the effective date of this final rule], an 
applicant may use the measurement point specified in section 
B36.3(a)(1) as an alternative.
    (b) Flyover reference noise measurement point: The point on the 
extended centerline of the runway that is 21,325 feet (6,500 m) from 
the start of the takeoff roll;
    (c) Approach reference noise measurement point: The point on the 
extended centerline of the runway that is 6,562 feet (2,000 m) from 
the runway threshold. On level ground, this corresponds to a 
position that is 394 feet (120 m) vertically below the 3 deg. 
descent path, which originates at a point on the runway 984 feet 
(300 m) beyond the threshold.

Section B36.4  Test noise measurement points.

    (a) If the test noise measurement points are not located at the 
reference noise measurement points, any corrections for the 
difference in position are to be made using the same adjustment 
procedures as for the differences between test and reference flight 
paths.
    (b) The applicant must use a sufficient number of lateral test 
noise measurement points to demonstrate to the FAA that the maximum 
noise level on the appropriate lateral line has been determined. For 
jet airplanes, simultaneous measurements must be made at one test 
noise measurement point at its symmetrical point on the other side 
of the runway. Propeller-driven airplanes have an inherent asymmetry 
in lateral noise. Therefore, simultaneous measurements must be made 
at each and every test noise measurement point at its symmetrical 
position on the opposite side of the runway. The measurement points 
are considered to be symmetrical if they are longitudinally within 
33 feet (10 meters) of each other.

Section B36.5  Maximum Noise Levels

    Except as provided in section B36.6 of this appendix, maximum 
noise levels, when determined in accordance with the noise 
evaluation methods of appendix A of this part, may not exceed the 
following:
    (a) For acoustical changes to Stage 1 airplanes, regardless of 
the number of engines, the noise levels prescribed under 
Sec. 36.7(c) of this part.
    (b) For any Stage 2 airplane regardless of the number of 
engines:
    (1) Flyover: 108 EPNdB for maximum weight of 600,000 pounds or 
more; for each halving of maximum weight (from 600,000 pounds), 
reduce the limit by 5 EPNdB; the limit is 93 EPNdB for a maximum 
weight of 75,000 pounds or less.
    (2) Lateral and approach: 108 EPNdB for maximum weight of 
600,000 pounds or more; for each halving of maximum weight (from 
600,000 pounds), reduce the limit by 2 EPNdB; the limit is 102 EPNdB 
for a maximum weight of 75,000 pounds or less.
    (c) For any Stage 3 airplane:
    (1) Flyover.
    (i) For airplanes with more than 3 engines: 106 EPNdB for 
maximum weight of 850,000 pounds or more; for each halving of 
maximum weight (from 850,000 pounds), reduce the limit by 4 EPNdB; 
the limit is 89 EPNdB for a maximum weight of 44,673 pounds or less;
    (ii) For airplanes with 3 engines: 104 EPNdB for maximum weight 
of 850,000 pounds or more; for each halving of maximum weight (from 
850,000 pounds), reduce the limit by 4 EPNdB; the limit is 89 EPNdB 
for a maximum weight of 63,177 pounds or less; and
    (iii) For airplanes with fewer than 3 engines; 101 EPNdB for 
maximum weight of 850,000 pounds or more; for each halving of 
maximum weight (from 850,000 pounds), reduce the limit by 4 EPNdB; 
reduce the limit by 4 EPNdB; the limit is 89 EPNdB for a maximum 
weight of 106,250 pounds or less.
    (2) Lateral, regardless of the number of engines: 103 EPNdB for 
maximum weight of 882,000 pounds or more; for each halving of 
maximum weight (from 882,000 pounds), reduce the limit by 2.56 
EPNdB; the limit is 94 EPNdB for a maximum weight of 77,200 pounds 
or less.
    (3) Approach, regardless of the number of engines: 105 EPNdB for 
maximum weight of 617,300 pounds or more; for each halving of 
maximum weight (from 617,300 pounds), reduce the limit by 2.33 
EPNdB; the limit is 98 EPNdB for a maximum weight of 77,200 pounds 
or less.

Section B36.6  Trade-Offs

    Except when prohibited by sections 36.7(c)(1) and 
36.7(d)(1)(ii), if the maximum noise levels are exceeded at any one 
or two measurement points, the following conditions must be met:
    (a) The sum of the exceedance(s) may not be greater than 3 
EPNdB;
    (b) Any exceedance at any single point may not be greater than 2 
EPNdB, and
    (c) Any exceedance(s) must be offset by a corresponding amount 
at another point or points.

Section B36.7  Noise Certification Reference Procedures and 
Conditions

    (a) General conditions:
    (1) All reference procedures must meet the requirements of 
section 36.3 of this part.
    (2) Calculations of airplane performance and flight path must be 
made using the reference procedures and must be approved by the FAA.

[[Page 45236]]

    (3) Applicants must use the takeoff and approach reference 
procedures prescribed in paragraphs (b) and (c) of this section.
    (4) [Reserved]
    (5) The reference procedures must be determined for the 
following reference conditions. The reference atmosphere is 
homogeneous in terms of temperature and relative humidity when used 
for the calculation of atmospheric absorption coefficients.
    (i) Sea level atmospheric pressure of 2116 pounds per square 
foot (psf) (1013.25 hPa);
    (ii) Ambient sea-level air temperature of 77  deg.F (25  deg.C, 
i.e. ISA+10  deg.C);
    (iii) Relative humidity of 70 per cent;
    (iv) Zero wind.
    (v) In defining the reference takeoff flight path(s) for the 
takeoff and lateral noise measurements, the runway gradient is zero.
    (b) Takeoff reference procedure:
    The takeoff reference flight path is to be calculated using the 
following:
    (1) Average engine takeoff thrust or power must be used from the 
state of takeoff to the point where at least the following height 
above runway level is reached. The takeoff thrust/power used must be 
the maximum available for normal operations given in the performance 
section of the airplane flight manual under the reference 
atmospheric conditions given in section B36.7(a)(5).
    (i) For Stage 1 airplanes and for Stage 2 airplanes that do not 
have jet engines with a bypass ratio of 2 or more, the following 
apply:
    (A): For airplanes with more than three jet engines--700 feet 
(214 meters).
    (B): For all other airplanes--1,000 feet (305 meters).
    (ii) For Stage 2 airplanes that have jet engines with a bypass 
ratio of 2 or more and for Stage 3 airplanes, the following apply:
    (A): For airplanes with more than three engines--689 feet (210 
meters).
    (B): For airplanes with three engines--853 feet (260 meters).
    (C): For airplanes with fewer than three engines--984 feet (300 
meters).
    (2) Upon reaching the height specified in paragraph (b)(1) of 
this section, airplane thrust or power must not be reduced below 
that required to maintain either of the following, whichever is 
greater:
    (i) A climb gradient of 4 per cent; or
    (ii) In the case of multi-engine airplanes, level flight with 
one engine inoperative.
    (3) For the purpose of determining the lateral noise level, the 
reference flight path must be calculated using full takeoff power 
throughout the test run without a reduction in thrust or power. For 
tests conducted before [the effective date of this final rule], a 
single reference flight path that includes thrust cutback in 
accordance with paragraph (b)(2) of this section, is an acceptable 
alternative in determining the lateral noise level.
    (4) The takeoff reference speed is the all-engine operating 
takeoff climb speed selected by the applicant for use in normal 
operation; this speed must be at least V2+10kt (V2+19km/h) but may 
not be greater than V2+20kt (V2+37km/h). This speed must be attained 
as soon as practicable after lift-off and be maintained throughout 
the takeoff noise certification test. For Concord airplanes, the 
test day speeds and the acoustic day reference speed are the minimum 
approved value of V2+35 knots, or the all-engines-operating speed at 
35 feet, whichever speed is greater as determined under the 
regulations constituting the type certification basis of the 
airplane; this reference speed may not exceed 250 knots. For all 
airplanes, noise values measured at the test day speeds must be 
corrected to the acoustic day reference speed.
    (5) The takeoff configuration selected by the applicant must be 
maintained constantly throughout the takeoff reference procedure, 
except that the landing gear may be retracted. Configuration means 
the center of gravity position, and the status of the airplane 
systems that can affect airplane performance or noise. Examples 
include, the position of lift augmentation devices, whether the APU 
is operating, and whether air bleeds and engines power take-offs are 
operating;
    (6) The weight of the airplane at the brake release must be the 
maximum takeoff weight at which the noise certification is 
requested, which may result in an operating limitation as specified 
in Sec. 36.1581(d); and
    (7) The average engine is defined as the average of all the 
certification compliant engines used during the airplane flight 
tests, up to and during certification, when operating within the 
limitations and according to the procedures given in the Flight 
Manual. This will determine the relationship of thrust/power to 
control parameters (e.g., N1 or EPR). Noise measurements 
made during certification tests must be corrected using this 
relationship.
    (c) Approach reference procedure:
    The approach reference flight path must be calculated using the 
following:
    (1) The airplane is stabilized and following a 3 deg. glide 
path;
    (2) For subsonic airplanes, a steady approach speed of 
Vref + 10 kts (Vref + 19 km/h) with thrust and 
power stabilized must be established and maintained over the 
approach measuring points. Vref is the reference landing 
speed, which is defined as the speed of the airplanes, in a 
specified landing configuration, at the point where it descends 
through the landing screen height in the determination of the 
landing distance for manual landings. For Concorde airplanes, a 
steady approach speed that is either the landing reference speed + 
10 knots or the speed used in establishing the approved landing 
distance under the airworthiness regulations constituting the type 
certification basis of the airplane, whichever speed is greater. 
This speed must be established and maintained over the approach 
measuring point.
    (3) The constant approach configuration used in the 
airworthiness certification tests, but with the landing gear down, 
must be maintained throughout the approach reference procedure;
    (4) The weight of the airplane at touchdown must be the maximum 
landing weight permitted in the approach configuration defined in 
paragraph (c)(3) of this section at which noise certification is 
requested, except as provided in Sec. 36.1581(d) of this part; and
    (5) The most critical configuration must be used; this 
configuration is defined as that which produces the highest noise 
level with normal deployment of aerodynamic control surfaces 
including lift and drag producing devices. at the weight at which 
certification is requested. This configuration includes all those 
items listed in section A36.5.2.5 of appendix A of this part that 
contribute to the noisiest continuous state at the maximum landing 
weight in normal operation.

Section B36.8  Noise Certification Test Procedures

    (a) All test procedures must be approved by the FAA.
    (b) The test procedures and noise measurements must be conducted 
and processed in an approved manner to yield the noise evaluation 
metric EPNL, in units of EPNdB, as described in appendix A of this 
part.
    (c) Acoustic data must be adjusted to the reference conditions 
specified in this appendix using the methods described in appendix A 
of this part. Adjustments for speed and thrust must be made as 
described in section A36.9 of this part.
    (d) If the airplane's weight during the test is different from 
the weight at which noise certification is requested, the required 
EPNL adjustment may not exceed 2 EPNdB for each takeoff and 1 EPNdB 
for each approach. Data approved by the FAA must be used to 
determine the variation of EPNL with weight for both takeoff and 
approach test conditions. The necessary EPNL adjustment for 
variations in approach flight path from the reference flight path 
must not exceed 2 EPNdB.
    (e) For approach, a steady glide path angle of 3 deg. 
 0.5 deg. is acceptable.
    (f) If equivalent test procedures different from the reference 
procedures are used, the test procedures and all methods for 
adjusting the results to the reference procedures must be approved 
by the FAA. The adjustments may not exceed 16 EPNdB on takeoff and 8 
EPNdB on approach. If the adjustment is more than 8 EPNdB on 
takeoff, or more than 4 EPNdB on approach, the resulting numbers 
must be more than 2 EPNdB below the limit noise levels specified in 
section B36.5.
    (g) During takeoff, lateral, and approach tests, the airplane 
variation in instantaneous indicated airspeed must be maintained 
within 3% of the average airspeed between the 10 dB-down 
points. This airspeed is determined by the pilot's airspeed 
indicator. However, if the instantaneous indicated airspeed exceeds 
3 kt (5.5 km/h) of the average airspeed over 
the 10 dB-down points, and is determined by the FAA representative 
on the flight deck to be due to atmospheric turbulence, then the 
flight so affected must be rejected for noise certification 
purposes.

    Note: Guidance material on the use of equivalent procedures is 
provided in the current advisory circular for this part.


    17. Remove and reserve appendix C of part 36.

Appendix G  [Amended]

    18. In appendix G, amend paragraph (f) of section G36.105 by 
removing the reference ``paragraph A36.3(e) of Appendix A'' and adding 
``paragraphs

[[Page 45237]]

A36.3.8 and A36.3.9 of Appendix A'' in its place.

Appendix H  [Amended]

    19. Amend appendix H as follows:
    a. In paragraph (d)(1) of section H36.101 by removing the reference 
to ``appendix B'' and adding ``appendix A'' in its place;
    b. Amend paragraph (c)(3) of section H36.111 of appendix H by 
removing the reference ``A36.3(f)(3)'' and adding ``A36.3.10.1'' in its 
place.
    c. Amend section H36.201 of appendix H in paragraph (a) 
introductory text by removing the references to ``appendix B'' and 
adding ``appendix A'' in its place; and in paragraph (b) by removing 
the reference to ``B36.5(a)'' and adding ``A36.4.3.1(a)'' in its place.

PART 91--GENERAL OPERATING AND FLIGHT RULES

    20. The authority citation for part 91 continues to read as 
follows:

    Authority: 49 U.S.C. 106(g), 1155, 40103, 40113, 40120, 44101, 
44111, 44701, 44709, 44711, 44712, 44715, 44716, 44717, 44722, 
46306, 46315, 46316, 46504, 46506-46507, 47122, 47508, 47528-47531, 
articles 12 and 29 of the Convention on International Civil Aviation 
(61 stat. 1180).


Sec. 91.801  [Amended]

    21. In paragraphs (a)(1) introductory text, (a)(2), (c), and (d) 
remove the word ``turbojet'' and add the words ``jet (turbojet)'' in 
its place.


Sec. 91.851  [Amended]

    22. In the definitions of ``Fleet'', ``Stage 2 airplane'', and 
``Stage 3 airplane'' remove the word ``turbojet'' and add the words 
``jet (turbojet)'' in its place.

    Issued in Washington, DC, on June 18, 2002.
Jane F. Garvey,
Administrator.
[FR Doc. 02-15835 Filed 7-5-02; 8:45 am]
BILLING CODE 4910-13-M