[Federal Register Volume 65, Number 133 (Tuesday, July 11, 2000)]
[Proposed Rules]
[Pages 42796-42832]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-16913]



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Part III





Department of Transportation





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Federal Aviation Administration



14 CFR Parts 21 and 36



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

  Federal Register / Vol. 65, No. 133 / Tuesday, July 11, 2000 / 
Proposed Rules  

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21 and 36

[Docket No. FAA-2000-7587; Notice No. 00-08]
RIN 2120-AH03


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of Proposed Rulemaking (NPRM).

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SUMMARY: The FAA is proposing changes to the noise certification 
standards for subsonic jet airplanes and subsonic transport category 
large airplanes. These proposed 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 proposed changes 
would 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 would simplify 
airworthiness approvals for import and export purposes.

DATES: Comments must be received on or before October 10, 2000.

ADDRESSES: Address your comments to the Docket Management System, U.S. 
Department of Transportation, Room Plaza 401, 400 Seventh Street, SW., 
Washington, DC 20590-0001. You must identify the docket number FAA-
2000-7587 at the beginning of your comments, and you should submit two 
copies of your comments. If you wish to receive confirmation that FAA 
received your comments, include a self-addressed, stamped postcard.
    You may also submit comments and you may review public dockets 
through the Internet at http://dms.dot.gov. You may review the public 
docket containing comments to these proposed regulations in person in 
the Dockets Office between 9:00 a.m. and 5:00 p.m., Monday through 
Friday, except Federal holidays. The Dockets Office is on the plaza 
level of the NASSIF Building at the Department of Transportation at the 
above address.

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 email at [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in this rulemaking by 
submitting written comments, data, views, or arguments. Comments on the 
possible environmental, economic, and federalism or energy related 
impact of the adoption of this proposal are welcomed.
    Comments should carry the regulatory docket or notice number and 
should be submitted in triplicate to the Rules Docket address specified 
above. All comments received and a report summarizing any substantive 
public contact with FAA personnel on this rulemaking will be filed in 
the docket. The docket is available for public inspection both before 
and after the closing date for receiving comments.
    Before taking any final action on this proposal, the Administrator 
will consider the comments made on or before the closing date for 
comments, and the proposal may be changed in light of the comments 
received.
    The FAA will acknowledge receipt of comments if commenters include 
a self-addressed, stamped postcard with the comments. The postcards 
should be marked ``Comments to Docket No. FAA-2000-7587.'' When the 
comments are received by the FAA, the postcards will be dated, time 
stamped, and returned to the commenters.

Availability of the NPRM

    An electronic copy of this document may be downloaded using a modem 
and suitable communications software from the FAA regulations section 
of the FedWorld electronic bulletin board service (telephone: (703) 
321-3339) or the Government Printing Office (GPO)'s electronic bulletin 
board service (telephone: (202) 512-1661).
    Internet users may reach the FAA's web page at http://www.faa.gov/avr/arm/nprm/nprm.htm or the GPO's web page at http://www.access.gpo.gov/nara for access to recently published rulemaking 
documents.
    Any person may obtain a copy of this document 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. Communications must identify the notice number or 
docket number of this NPRM.
    Persons interested in being placed on the mailing list for future 
rulemaking documents should request from the above office a copy of 
Advisory Circular No. 11-2A, Notice of Proposed Rulemaking Distribution 
System, which describes the application procedure.

Background

Current Regulations

    Under 49 U.S.C. 44715, the Administrator of the Federal Aviation 
Administration is directed to prescribe ``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 (part 36) contains the FAA's noise standards and 
regulations that apply to the issuance of type certificates for all 
types of aircraft. Subparts A, B and C and appendices A, B and C of 
part 36 contain the requirements and standards that 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 Joint Aviation Authorities (JAA) 
Council, which consists of JAA members from European countries and the 
FAA, the FAA Administrator committed the FAA to support the 
harmonization of the U.S. regulations with the Joint Aviation 
Regulations (JAR). The Joint Aviation Regulations are being 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 has tasked ARAC with noise certification issues. These issues 
involve the harmonization of 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 of part 36, and harmonizing them with the corresponding applicable 
provisions

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of JAR 36. The working group was asked to consider the current 
international standards and recommended practices, as issued under 
International Civil Aviation Organization (ICAO), Annex 16, Volume 1, 
and its associated Technical Manual, as the basis for development of 
these harmonization proposals. A recommendation for amending part 36 
was forwarded to the ARAC. After due consideration including a meeting 
open to the public on May 18, 2000, this recommendation agreed to by 
ARAC was forwarded, in the form of a draft NPRM, to the FAA for 
consideration.

Synopsis of the Proposal

    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 notice of proposed rulemaking includes changes to part 36 in 
three major categories. First, there are substantive changes to 
technical material, such as proposing a revised method for 
demonstrating the lateral noise certification level for propeller-
driven large airplanes. These changes are discussed individually in 
this preamble. Second, there are many proposed changes to regulatory 
text that would 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 proposed changes to the 
section designations of current Appendices A, B, and C of part 36 that 
would more closely align part 36 and JAR 36 formats. Changes in this 
category would have no substantive effect on the regulatory standards 
of part 36. The changes in part 36 appendices designation are shown in 
a tabular format that identifies current part 36 appendices sections 
and the corresponding section of the proposed 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 proposed 
amendments that will cover the substantive changes being proposed for 
the regulatory standards of part 36 and its appendices. Sections that 
are proposed for redesignation, but not substantively changed, will not 
be discussed, but will appear only in the redesignation table that 
follows the section-by-section discussion. Throughout the proposed 
amendment, the term ``jet'' has been used when referring to turbojet 
and turbofan engines. This would change the terminology in current part 
36, which uses the term ``turbojet'' when referring to both turbojet 
and turbofan engines. This change would result in the same terminology 
usage by both part 36 and JAR 36, when referring to turbojet and 
turbofan engines.

Section 36.1

    The FAA is proposing to remove Sec. 36.1(d)(3). This section should 
have been removed by Amendment 36-10 (43 FR 28406, June 29, 1978), 
which redesignated Sec. 36.1(d)(3) as Sec. 36.1(d)(1)(iii).
    In Sec. 36.1(f)(1), the terms ``takeoff'' and ``sideline'' are 
proposed to be replaced with the terms ``flyover'' and ``lateral'', 
respectively. This change would harmonize the terminology based on the 
international standard.

Section 36.2

    Section 36.2, ``Special retroactive requirements'' would be 
removed. Section 36.2 requires that the noise certification applicant 
show compliance to the part 36 amendment that is in effect on the date 
of certification. This requirement was included in part 36 when the FAA 
did not have the authority to prevent the issuance of a type 
certificate for an aircraft for which available and reasonable noise 
reduction design practices had not been incorporated. The FAA 
subsequently received this authority under the Noise Control Act of 
1972; the retroactive requirement contained in Sec. 36.2 is no longer 
necessary. This change would harmonize the applicability designation of 
part 36 with that contained in Sec. 1.7 of ICAO annex 16, Chapter 1. In 
conjunction with the proposed removal of the special retroactive 
requirements of part 36 Sec. 36.2, this notice proposes changes to 
Secs. 21.17 and 21.101(a) of part 21 of this chapter to remove 
references to part 36 that are contained in these sections of part 21.

Section 36.6

    The FAA proposes to add five specifications to the incorporated 
matter under Sec. 36.6. These specifications are referred to under 
proposed section A36.3, which would update 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 proposed Sec. 36.6.

Sections 36.101 and 36.103

    Two sections, 36.101, Noise measurement, and 36.103, Noise 
evaluation, would be replaced with a new Sec. 36.101, Noise measurement 
and evaluation. The proposed Sec. 36.101 reflects the proposal to 
combine the material contained in current Appendix A and Appendix B 
into proposed Appendix A. This proposed change would more closely align 
part 36 and JAR 36 formats without any substantive effect. Also for the 
purpose of aligning the formats of part 36 and JAR 36, the FAA proposes 
to redesignate Sec. 36.201 as Sec. 36.103. Current subpart C would be 
reserved.

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

    The proposed Appendix A to part 36, Aircraft Noise Measurement and 
Evaluation under Sec. 36.101, would replace current Appendix A, 
Aircraft Noise Measurement under Sec. 36.101, and Appendix B, Aircraft 
Noise Evaluation under Sec. 36.103. The harmonization objective is to 
develop seamless part 36 and JAR 36 regulations that reflect ICAO Annex 
16 to the extent possible. The text of JAR 36, Appendix A, is 
essentially a copy of Annex 16, Appendix 2. The proposed Appendix A to 
part 36 was developed with the intent of maintaining a section format 
consistent with JAR 36, Appendix A and ICAO Annex 16, Appendix 2.

Appendix A36.1  Introduction

    A new section A36.1.2 would be added to state that the noise 
certification instructions and procedures given are intended to ensure 
uniform results and to permit comparison between tests of various types 
of aircraft conducted in various geographical locations.

Appendix A36.2  Noise Certification Test and Measurement Conditions

    Proposed section A36.2 would replace current section A36.1. This 
proposed section describes the conditions under which noise 
certification testing would be conducted and the measurement procedures 
that would be required.
    Under the proposal, current section A36.5(e)(4), that addresses the 
use of equivalent procedures, would be deleted. The key requirement of 
the section, that equivalent procedures must be FAA-approved, is 
already addressed in the regulatory text of Sec. 36.101. Additional 
information on the use of

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equivalent procedures would be provided in the note contained in 
section A36.2.1.1. Therefore, section A36.5(e)(4) would be deleted 
since its content would be addressed in Sec. 36.101.
    A note in section A36.2.1.1 would reference the guidance material 
on the use of equivalent procedures contained in Advisory Circular 36-
4C, ``Noise Standards: Aircraft Type and Airworthiness Certification''. 
Current AC36-4B, ``Noise Certification Handbook'', contains guidance 
material on the use of equivalent procedures. AC36-4B will be revised 
and significantly changed in format and content, and will be designated 
AC36-4C, ``Noise Standards: Aircraft Type and Airworthiness 
Certification.'' The FAA intends to issue the new AC36-4C concurrently 
with the final rule that results from this notice. The AC36-4C is 
referred to as ``the current Advisory Circular for this part'' 
throughout the proposed regulatory text in order to avoid the need for 
formal rulemaking any time the Advisory Circular is revised. Throughout 
this preamble, however, the Advisory Circular is referred to as 
Advisory Circular 36-4C.
    Most of proposed section A36.2 is moved from sections A36.1, A36.5 
and A36.9. Under the proposal, the material in current section 
A36.1(c)(1) would be moved to proposed 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) would be moved 
to proposed section A36.2.2.2(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 would still be required 
to be conducted in conformance with the operational temperature limit 
for the noise measuring equipment being used.
    Proposed section A36.2.2.2(c), does not contain the current section 
A36.1(c)(3) provision that permits expanded atmospheric attenuation 
rates when the dew point and dry bulb temperatures used for obtaining 
relative humidity are measured with a device which is accurate to 
within 0.5  deg.C. This allowance for expanded atmospheric 
attenuation rates is already permitted as an equivalent procedure by 
AC36-4B, and will continue to be permitted as an equivalent procedure 
in the revision to AC36-4B (i.e., AC36-4C). The result would be no 
change in the allowance of expanded atmospheric attenuation rates. This 
change is proposed to meet the harmonization objective to more closely 
align part 36 and JAR 36 formats.
    The requirement to obtain meteorological measurements within ``25 
minutes'' of each noise test measurement as required in current section 
A36.9(b)(3) would be changed to ``30 minutes'' in proposed 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 with which to assess this minimal time increment. This 
change is being proposed to achieve harmonization by adopting a single 
international standard.
    Current section A36.9(d)(3) would be revised and moved to section 
A36.2.2.3. This amendment would change the method used to establish 
layer depth to a single international standard. Part 36 does not 
provide specific criteria for determining layer depth, except to 
require that it be no greater than 100 ft. The proposed criteria for 
determining layer depth 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 proposal, 
the minimum layer depth would be 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 proposed changes to this section are intended to update the 
requirements for measurement and analysis systems to address the latest 
standards and equipment technology. The changes were drafted by an 
international task group, that has years of knowledge and experience in 
the noise certification of airplanes, and was assembled to update the 
ICAO Annex 16 requirements for measurement and analysis systems. The 
proposed changes in section A36.3 incorporates the international task 
group's recommendations, which were agreed to by Working Group 1 of the 
ICAO Committee on Aviation Environmental Protection (ICAO/CAEP). 
Further, the proposed changes are intended to harmonize with the 
international standard, Annex 16. The primary purpose of this work 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 
overall.
    Proposed section A36.3 includes the following specific changes to 
current section A36.3. Current section A36.3 does not include 
definitions. Section A36.3.1, Definitions, would be added to define the 
terms used in proposed section A36.3. Under the proposal, section 
A36.3.2, Reference environmental conditions, would be added for 
specifying the performance of a measurement system.
    Section A36.3.3.2 would specify anti-alias requirements for 
measurement systems that include analog to digital signal conversion.
    Proposed section A36.3.4.1 would add a requirement that windscreen 
insertion loss not exceed 1.5 dB. In addition, proposed 
section A36.3.9.10 would specify allowable changes in windscreen 
insertion loss.
    Proposed sections A36.3.5.3 and A36.3.5.4 would 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). Sections A36.3.5.3 and A36.3.5.4 
would 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.
    Proposed section A36.3.6.3 would add a tolerance for frequency 
response of the measurement system.
    For analog tape, proposed section A36.3.6.4 would add a 
0.5 dB tolerance for amplitude fluctuations of a recorded 1 
kHz signal.

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    Proposed section A36.3.6.5 would add a tolerance for amplitude 
linearity, at several specific frequencies, for the measurement system 
(exclusive of the microphone.)
    Proposed section A36.3.6.6 would require 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. A similar requirement in current part 36, section 
A36.(c)(3)(i), is 10 dB.
    Proposed section A36.3.6.8 would add a requirement for an overload 
indicator in the recording and reproducing system.
    Proposed section A36.3.6.9 would allow 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).
    Proposed section A36.3.7.2(e) would add a requirement that the 
analyzer operate in real time from 50 Hz through at least 12 kHz.
    Proposed section A36.3.7.3 would specify 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. Proposed section 
A36.3.7.3 would also require that filter bandwidth adjustments be 
determined in accordance with IEC 61260. The IEC method requires that 
the adjustment be based on more frequencies than are required under 
current part 36.
    Proposed section A36.3.7.4 would contain a correction to the slow 
time-weighting characteristics in current section A36.3(d)(5)(ii) and 
(iii). Section A36.3.7.6 would specify 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 readout is 
characterized must be the midpoint of the averaging period.
    Proposed section A36.3.7.5 would specify a continuous exponential 
averaging process equation through which simulated slow weighted sound 
pressure levels can be obtained. Section A36.3.7.5 would also specify 
an equation that results in an approximation of continuous exponential 
averaging.
    Section A36.3.7.7 would require that the analyzer resolution must 
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.
    Proposed section A36.3.9.1 would require 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. This change is necessary to enable the 
FAA to determine whether these calibration adjustments have been 
applied correctly.
    Proposed section A36.3.9.3 would allow the free-field corrections 
based on grazing incidence to be applied when the sound incidence angle 
is within 30 degrees of grazing incidence.
    Proposed section A36.3.9.4 would require that at least 30 seconds 
of pink noise be recorded for analog tape recorders; the current 
section A36.3(e)(4)(ii) requirement is for at least 15 seconds of pink 
noise. This change would result in a more accurate pink noise 
correction and would harmonize with the international standard.
    Proposed section A36.3.9.6 would require that attenuator accuracy 
be within 0.1 dB. Section A36.3(b)(6) currently requires that 
attenuator accuracy be within 0.2 dB. The proposed rule would require 
that calibration be checked within six months of each test series. The 
current rule does not specify a time period within which calibration 
must be checked.
    Proposed sections A36.3.9.5 and A36.3.9.7 would change calibration 
requirements for the pink noise generator and sound calibrator to allow 
calibration to occur within six months preceding or succeeding the test 
instead of requiring it to be within the preceding six months as 
required by current section A36.3(e)(7).
    Proposed section A36.3.9.7 would add a new calibration requirement 
that limits the change in output of the sound calibrator to not more 
than 0.2 dB, as compared to the previous calibration.
    Proposed section A36.3.9.8 would allow for the use of sound 
calibrators other than pistonphones, as specified by current section 
A36.3(e)(4). Section A36.3.8.1 would specify the class 1L requirements 
of IEC 60942, entitled ``Electroacoustics--Sound calibrators'', as the 
minimum standard for the sound calibrator.
    Proposed section A36.3.9.9 would add a requirement for the 
recording medium (e.g., tape reel) to carry at least a 10-second sound 
pressure level calibration at its beginning and end. This proposed 
change would more precisely define 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) would be moved to AC36-4C. The 
noy values contained in Table B-1 can be calculated from the equations 
contained in proposed section A36.4.7.3.
    A minor technical change is proposed for the Perceived Noise Level 
(PNL) equation in proposed 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 proposed 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'', would be 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 proposed section A36.4.2.1(c).
    Proposed section A36.4.5.2 would change the value of ``d'' from 1.0 
seconds to 0.5 seconds to reflect current standard practice. Parallel 
changes are proposed for 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 would have 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 would be moved to AC36-4C.
    The FAA is proposing the deletion of 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. 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 
has erroneously remained in part 36.
    In addition, current section B36.9(f) would also be deleted. The 
text contained in current section B36.9(f) was added to part 36 in 
Amendment 36-5 to distinguish between the procedure for determining 
duration for applications made before and after September 17, 1971. 
This distinction is no longer necessary if current section B36.9(e) is 
deleted as proposed.
    Section A36.5 Data Reporting. Proposed section A36.5.2 would 
require

[[Page 42800]]

that the data specified under section A36.5.2 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. Proposed section A36.5.2.5 
would also identify the specific airplane configuration items and 
engine operating parameters that must be reported. Each of these 
configuration items and parameters can affect the airplane noise 
signature. The reporting requirement 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. Further, these configuration items and 
parameters are also included in the international standard. Their 
addition to part 36 would promote harmonization.
    Proposed section A36.5.2.5(c) would require 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 an item that could influence measured noise 
levels. Proposed section A36.5.2.5(d) would require that airbrake and 
propeller pitch angle also be reported. Proposed sections A36.5.2.5(e), 
(f), and (j) would, 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.
    Proposed section A36.5.2.5(h)(2) would require reporting of engine 
performance parameters specifically related to propeller-driven large 
airplanes.
    Current section A36.5(d)(3) does not permit an effective perceived 
noise level (EPNL) to be computed or reported from data that more than 
four one-third octave bands in any spectrum within the 10 dB-down 
points have been excluded from the EPNL computation. This section would 
be 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. Proposed section A36.3.9.12 
specifies the ambient noise level limitations that would require 
corrections (adjustments) to be made, and also references AC36-4C, 
which contains an acceptable procedure for removing the affects of 
ambient noise.

Section A36.6  Nomenclature: Symbols and Units

    Under the proposal, current section A36.7, Symbols and units, would 
be replaced by revised section A36.6, Nomenclature: Symbols and units. 
The proposed section would incorporate Annex 16 symbols and units, 
while retaining the English units. This change is proposed to more 
closely align part 36 with JAR 36. No substantive technical changes to 
the regulatory standards of part 36 are anticipated to result from 
incorporation of the Annex 16 symbols and units.

Section A36.7  Sound Attenuation in Air

    Currently, atmospheric attenuation rates of sound with distance 
must 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). Under the proposal, section 
A36.7.2 would contain 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. This proposed change would 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) are not included in proposed section A36.9.1. The 
distinction is no longer relevant, given the evolution of data 
correction procedures since part 36 was originally promulgated in 1969 
and 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 gain FAA approval of any planned or 
anticipated data correction that is not a mandatory correction 
procedure under part 36.
    Under the proposal, current section A36.1(b)(3), which 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, would be 
deleted because it is obsolete. A 20-foot height allowance/tolerance 
could change the final EPNL value by several tenths of a dB under some 
circumstances. Under current 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 
proposed section A36.9.
    Proposed section A36.9.1.1(d) would 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. Thus, the proposed section would specify that, 
``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 quantify the 
effects of the airspeed adjustment on resulting certification noise 
levels.''
    The symbols and figures used to describe the takeoff and approach 
profiles in current sections A36.11(b) and (c), would be replaced by 
the JAR 36 symbols and figures that have been incorporated into 
proposed section A36.9.2. There would be no substantive changes to the 
takeoff and approach profile technical requirements as a result of 
these changes.
    Proposed section A36.9.3.2.1 provides equations that would 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) would be moved to section 
A36.9.3.2.2 and revised to provide that the adjustment for multiple 
peak values of tone-corrected perceived noise level (PNLT) is based 
upon the difference in corrected PNLT values, rather than upon EPNL as 
in the current part 36. This change would more clearly define the 
intent of the multiple peak correction.
    Under proposed section A36.9.3.3.2, a correction term to account 
for the difference between test and reference airplane airspeeds would 
be added to the duration correction (2) contained in current 
section A36.11(e). The speed correction term would be defined as 10 log 
(V/Vr), where V is the airplane test speed and Vr 
is the airplane reference speed. This proposed change specifies the 
speed correction that is a requirement of current section A36.11(f)(1).

[[Page 42801]]

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

    Proposed appendix B would include the material from current 
appendix C. The objective is to harmonize proposed appendix B, and JAR 
36, Section 1, Subpart B. The proposed appendix B is essentially the 
same as JAR 36, section 1, subpart B.

Section B36.3  Reference Noise Measurement Points.

    Under the proposal, the material in current section C36.3 would be 
moved to section B36.3 and revised as follows. The term ``takeoff'' in 
current section C36.3(a) would be replaced with the term ``flyover'' in 
proposed section B36.3(b).) The term ``sideline'' in current section 
C36.3(c) would be replaced with ``lateral'' in proposed section 
B36.3(a). These terminology changes would harmonize the part 36 
terminology with that used in JAR 36 and Annex 16.
    Proposed section B36.3(a)(2) includes a simplified test procedure 
that may be used in determining the sideline (lateral) noise level for 
propeller-driven large airplanes in demonstrating the sideline 
(lateral) noise certification level. 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 C36.3C, 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 large 
airplane. By measuring full-power noise at a predetermined point 
(650meters) below the takeoff flight path, many of the difficulties 
which 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 certification 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 simplified test procedure is 
proposed to be available as an alternative to the current section 
C36.3(c) method for tests conducted before March 20, 2002, after which 
it would become the sole method for demonstrating sideline (lateral) 
noise level compliance.
    Current section C36.3(b) would be moved to section B36.3(c) and 
text would be added to define the approach measurement point relative 
to the runway threshold. This change would more clearly describe the 
geometric relationship between the test airplane and the ground, and 
would further harmonize part 36 and JAR 36.

Section B36.4  Test Noise Measurement Points

    As proposed, most of the requirements of current section 
A36.1(b)(7) would be moved to proposed section B36.4(b). 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). Under the proposed rulemaking, this procedure 
would be moved to the guidance material in AC 36-4C as an equivalent 
procedure for demonstrating the sideline (lateral) noise certification 
level. This change would further harmonize part 36 and JAR 36 and would 
have no substantive effect.
    Proposed section B36.4(b) would require that, in demonstrating the 
sideline (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 proposed because of the asymmetric 
nature of propeller noise. Because of the possibility of lateral noise 
asymmetry, part 36 has required simultaneous measurements at one test 
measurement point opposite the main lateral measurement line. In the 
case of propeller-driven airplanes, 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 the runway from the main lateral line. This change 
would further harmonize part 36 and JAR 36.

Section B36.5  Maximum Noise Levels

    The material in current section C36.5 would be moved to proposed 
section B36.5 and revised to include minor format and language changes 
to harmonize with JAR 36. Amendment 36-15 (53 FR 16360, May 6, 1988) 
removed section C36.5(c); the reference to section C36.5(c) in current 
section C36.5(a) should have been removed under that amendment but it 
was not. The reference to section C36.5(c) is not included in this 
proposal.
    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 is a change in terminology that 
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 material in current section C36.5(b) would be moved to proposed 
section B36.6 and the reference to section 36.7(d)(3)(i)(B), in current 
section C36.5(b), would be changed to section 36.7(d)(1)(ii). This 
section reference should have been changed by Amendment 36-15 (53 FR 
16360, May 6, 1988). This error is corrected by this proposed revision.

Section B36.7  Noise Certification Reference Procedures

    The material addressing takeoff and approach reference and test 
limitations in current sections C36.7 and C36.9 would be moved to 
section B36.7, addressing takeoff and approach reference procedures, 
and section B36.8, addressing takeoff and approach test procedures. 
This material would also be revised as discussed in the following 
paragraphs.
    Proposed section B36.7(b)(1) requires the use of ``average engine'' 
performance in defining the takeoff thrust for the reference takeoff 
procedures. This revision of current section C36.7(b)(2) would further 
harmonize the takeoff reference procedure, and would serve to eliminate 
confusion in compliance with the requirement. This change would also 
further standardize part 36 and JAR 36 regulations.
    Proposed section B36.7(b)(1) would also specify ``Takeoff thrust/
power'' as the maximum available for normal operations as scheduled in 
the performance section of the airplane flight manual for the reference 
atmospheric conditions given in proposed section B36.7(a)(5).
    Currently section C36.7(b)(2) specifies different minimum cutback 
altitudes for jet powered and non-jet powered airplanes. Proposed 
section B36.7((b)(1)(ii) would contain the same minimum cutback 
altitude for all airplanes, the same altitude specified in current 
section C36.7(b)(2) for jet airplanes. Since the selection of the

[[Page 42802]]

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 would not have a substantive effect in practice, since 
cutback initiation heights greater than 1,500 feet are generally chosen 
for propeller-driven airplanes. Thus, the cutback initiation heights 
generally chosen are greater than both the current and proposed part 36 
minimum cutback height requirements.
    Under the proposal, the requirements of section A36.1(b)(2) is 
moved to section B36.7(b)(3) and revised to require that, for tests 
conducted after March 19, 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 is proposed to reflect 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 would be optional 
for tests conducted before March 20, 2002. This change would mainly 
effect three and four engine airplanes.
    The takeoff reference speed requirement specified in current 
section C36.7(e)(2) would be revised to be consistent with the takeoff 
reference speed contained in JAR 36 and Annex 16. The all-engine 
operating climb speed range (V2+10 to V2+20 kts) specified in proposed 
section B36.7(b)(4) represents the typical range of takeoff initial 
climb speeds seen in normal operation for most airplanes. For some 
airplanes, this proposed 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.
    Proposed section B36.7(b)(5) adds the meaning of configuration. 
This is not a change in requirement. Proposed section B36.7(b)(5) is 
intended to clarify the meaning and includes specific configuration 
elements, based on certification experience, that can have an effect on 
noise source.
    Proposed 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.
    Under the proposal, current section C36.9(e)(1), reference approach 
speed, would be 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. This proposal was included in Notice 
95-17, published on January 18, 1996 (61 FR 1260), in which 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. Under Notice 95-17, a definition of 
VREF would be included in 14 CFR part 1. Notice 95-17 has 
not been issued as a final rule. If a final rule based on Notice 95-17 
is not issued before this notice becomes a final rule; the definition 
of VREF (i.e., 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) would be added to part 36. The proposed change to 
section C36.9(e)(1) would also be consistent with an anticipated change 
to ICAO/Annex 16 that is expected to be recommended by Working Group 1 
of the ICAO Committee on Aviation Environmental Protection (CAEP) in 
conjunction with the current CAEP work program cycle. Under this 
proposed change, existing section C36.9(e)(1) would be redesignated as 
section B36.7(c)(2).
    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. Under the proposal, this specific 
requirement would be removed, and instead, proposed section A36.9.3.4 
would require that source noise adjustments be applied to account for 
any difference, between test and reference conditions, in engine 
parameters that affect engine noise (e.g., corrected low pressure rotor 
speed). This proposed change would meet the intent of the current part 
36 requirement and would also further harmonize with JAR 36.

Section B36.8--Test Procedures

    The current section A36.1(d)(5) and A36.1(d)(7), limitations on the 
difference between the test weight and the maximum takeoff/approach 
weight for which noise certification is requested, would be replaced by 
the limitation in proposed section B36.8(d). The current section 
A36.1(d)(5) and A36.1(d)(7) 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. Proposed 
section B36.8(d) would 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.
    Under the proposal, current section A36.5(d)(5) would be 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 C noise levels, for the purpose of determining adjustment 
limits. Several interpretations of the current section A36.5(d)(5) 
requirement are possible as to whether the proposal represents a more 
stringent or less stringent adjustment limitation as compared with the 
current limitation. The FAA believes that the proposed change to remove 
the tradeoff provision from the current limitation and base the 
proposed limitation solely on the difference between the adjusted noise 
levels and the maximum noise levels in proposed B36.5 meets the intent 
of the adjustment limitation, as stated above, and clarifies ambiguity 
in its interpretation. The proposed change would also result in 
harmonization of the adjustment limitation with that in JAR 36 and ICAO 
Annex 16.
    Proposed section B36.8(g) would 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. Proposed section B36.8(g) would 
specify that during takeoff,

[[Page 42803]]

lateral, and approach tests, the airplane variation in instantaneous 
indicated airspeed must be maintained within +/-3% of the average 
airspeed between the 10dB-down points. Under the proposal, the 
instantaneous indicated 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 10dB-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.

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

Current Section G36.105(f)

    The proposal would change the designation of the reference to 
current part 36 section A36.3(e) to A36.3.8 and A36.3.9 to maintain the 
correct cross-reference.

Appendix H Noise Requirements for Helicopters Under Subpart H

Current Section H36.111(c)(3)

    The proposal would change the designation of the reference to 
current part 36 section A36.3(f)(3) to A36.3.9.11 to maintain the 
correct cross-reference.

Current section H36.201

    The proposal would change the designation of the reference to 
current part 36 section B36.5(a) to A36.4.3.1(a) to maintain the 
correct cross-reference.

Redesignation Table for Proposed 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)...............................  B36.7(b)(1)(iii)
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
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)
                                            AC36-4C
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).............................  A36.3.9.11
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)(1)(vi),
                                            B36.7(c)(1)(i),
                                            B36.7(c)(1)(iv)
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)...............................  A36.3.9.12
A36.5(d)(4)...............................  A36.3.9.12
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(c)
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), AC36-4C
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, Step 1
B36.3(b)..................................  A36.4.2.1, Step 2
B36.3(c)..................................  A36.4.2.1, Step 3,
                                            AC 36-4B
B36.5.....................................  A36.4.3.1
B36.5(a)..................................  A36.4.3.1, Step 1
B36.5(b)..................................  A36.4.3.1, Step 2
B36.5(c)..................................  A36.4.3.1, Step 3
B36.5(d)..................................  A36.4.3.1, Step 4
B36.5(e)..................................  A36.4.3.1, Step 5
B36.5(f)..................................  A36.4.3.1, Step 6
B36.5(g)..................................  A36.4.3.1, Step 7
B36.5(h)..................................  A36.4.3.1, Step 8
B36.5(i)..................................  A36.4.3.1, Step 9
B36.5(j)..................................  A36.4.3.1, Step 10
B36.5(k)..................................  A36.4.3.1, Step 10
B36.5(l)..................................  A36.4.3.1, Step 10
B36.5(m)..................................  A36.4.3.1, Step 10
                                            Note, AC36-4C
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).................................  A36.4.6.1
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)(1)(i)............................  B36.7(b)(1)(i)
C36.7(b)(1)(ii)...........................  B36.7(b)(1)(i)
C36.7(b)(2)(i)............................  B36.7(b)(1)(i)
C36.7(b)(2)(ii)...........................  B36.7(b)(1)(i)
C36.7(b)(2)(iii)..........................  B36.7(b)(1)(i)
C36.7(b)(2)(iv)...........................  B36.7(b)(1)(i)
C36.7(c)..................................  B36.7(b)(1)(ii)
C36.7(d)..................................  B36.7(b)(1)(v)
C36.7(e)(1)...............................  B36.7(b)(1)(iv)
C36.7(e)(1) Next to last sentence.........  B36.8(g)
C36.7(e)(2)...............................  B36.7(b)(1)(iv)
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)(1)(iii) &
                                             B36.7(c)(1)(v)
C36.9(c)..................................  B36.7(c)(1)(i),
                                            B36.7(c)(iii)
C36.9(d)..................................  Deleted
C36.9(e)(1)...............................  B36.7(c)(1)(ii)
C36.9(e)(2)...............................  B36.7(c)(1)(ii)
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), A36.9(b)(1)
A36.2.3...................................  A36.1(d)
A36.2.3.1.................................  A36.1(d)(2)
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

[[Page 42804]]

 
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)
A36.3.9.11................................  A36.3(f)(2-4)
A36.3.9.12................................  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
A36.4.6.1.................................  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...............................  A36.9(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...............................  B36.11(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), C36.7(b)(2)
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)...............................  A36.5(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)...............................  A36.5(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)(5-7)
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

    In this NPRM, Noise Certification Standards for Subsonic Jet 
Airplanes and Subsonic Transport Category Large Airplanes, Part 36, 
proposed Secs. A36.5.2 and A36.5.2.5 contain information collection 
requirements. As required by the Paperwork Reduction Act of 1995 (44 
U.S.C. 3507(d)), the FAA has submitted a copy of these proposed 
sections to the Office of Management and Budget (OMB) for its review.
    The information to be collected is needed for the applicant's noise 
compliance report that is required by the Aircraft Noise Abatement Act 
of 1968. This statute authorized FAA to prescribe standards for the 
measurement of aircraft noise and to prescribe regulations providing 
for the control and abatement of aircraft noise. The noise compliance 
report information is part of the aircraft certification test. The 
collected information is incorporated into the noise compliance report 
that is provided to and approved by the FAA. The annual burden for 
Sec. A36.5.2 is estimated to range from $80  x  80 hours at $6,400 per 
noise certification project to $100  x  160 hours at $16,000 per noise 
certification project. The annual burden for Sec. A36.5.2.5 is 
estimated to range from $500 (5 hours  x  $100 per hour) to $2,000 (25 
hours  x  $80 per hour) per certification. If proprietary information 
is submitted, it will be protected in accordance with appropriate laws.
    The agency is soliciting comments to (1) evaluate whether the 
proposed collection of information is necessary; (2) evaluate the 
accuracy of the agency's estimate of the burden; (3) enhance the 
quality, utility, and clarity of the information to be collected; and 
(4) minimize the burden of the collection of information on those who 
are to respond, including through the use of appropriate automated, 
electronic, mechanical, or other technological collection techniques or 
other forms of information technology (for example, permitting 
electronic submission of responses).
    Individuals and organizations may submit comments on the 
information collection requirement by September 11, 2000 and should 
direct them to the address listed in the ADDRESSES section of this 
document.
    According to the regulations implementing the Paperwork Reduction 
Act of 1995, (5 CFR 1320.8(b)(2)(vi)), an agency may not conduct or 
sponsor, and a person is not required to respond to, a collection of 
information unless it displays a currently valid Office of Management 
and Budget (OMB) control number. The public will be notified of the OMB 
control number when it is assigned.

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. If this proposal is adopted, the FAA intends to file these 
differences with ICAO.
    Wind Speed. Section A36.2.2.2(e) of the proposal requires that 
tests be carried out under atmospheric conditions where the average 
wind velocity 10 meters above ground does not exceed 12 knots and the 
crosswind velocity for the airplane does not exceed 7 knots. Section 
A36.2.2.2(e) of the proposal 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

[[Page 42805]]

knots during the 10 dB down time interval. Section 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 does not agree to adopt this Annex 16 
provision because it could result in tests being conducted in windspeed 
conditions that exceed those currently permitted under part 36; the 
effect of these higher wind conditions might have on the resulting 
noise levels could not be determined based on the information that was 
available to the harmonization working group.
    Adjustments to PNL and PNLT. In adjusting measured sound pressure 
level data to reference conditions, section 9.3.2.1 of Annex 16 
Appendix 2 requires 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 did not agree to adopt this 
provision. The FAA's view is 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 adjustments are applied to account for the difference 
between the test and reference airplane heights above the noise 
measurement point.
    Design characteristics that require different reference procedures. 
Section 3.6.1.4 of ICAO Annex 16, Appendix 2 permits the certificating 
authority to approve reference procedures that depart from those 
contained in section 3.6.2 and 3.6.3 of Annex 16 Appendix 2 when design 
characteristics of an airplane would prevent flight from being 
conducted in accordance with the 3.6.2 and 3.6.3 reference procedures. 
FAA did not agree to adopt this provision since it views the need to 
depart from the specified reference procedures due to airplane design 
characteristics as an indication that part 36 may not be appropriate 
for a given airplane. In this case, under U.S. procedures, the 
exemption or rulemaking processes, which include a public comment 
period would be followed to develop an appropriate noise certification 
basis.
    Noise Certificates. Section 1.2 of ICAO Annex 16, Chapter 1 
specifies that the documents attesting 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. However, under 49 U.S.C. 
44702, the FAA is not authorized to issue Noise Certificates. Section 
36.1581 of part 36 requires that the certificated noise levels be 
included in the Airplane Flight Manual. However, the FAA does not 
require the Airplane Flight Manual to be carried in the airplane. An 
operations manual that does not contain certificated noise levels is 
carried in some airplanes. The FAA is aware of a number of cases in 
which airplane operators had difficulty in substantiating airplane 
noise compliance status to the satisfaction of airport authorities. The 
FAA invites 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.

Economic Evaluation

    Proposed changes to Federal regulations undergo several economic 
analyses. First, Executive Order 12866 directs that each Federal agency 
propose or adopt a regulation only upon a 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 also requires agencies to consider international standards and, 
where appropriate, use them as the basis of U.S. standards. And 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 that include a Federal mandate likely to result in the 
expenditure by State, local or tribal governments, in the aggregate, or 
by the private sector, of $100 million or more annually (adjusted for 
inflation.)
    In conducting these analyses, the FAA has determined that this rule 
(1) has benefits which do justify its cost, is not a ``significant 
regulatory action'' as defined in the Executive Order and the 
Department of Transportation's (DOT) Regulatory Policies and 
Procedures; (2) will not have a significant impact on a substantial 
number of small entities; (3) reduces barriers to international trade; 
and (4) does not impose an unfunded mandate on state, local, or tribal 
governments, or the private sector. These analyses, available in the 
docket, are summarized below.

Costs

    Many of the changes in the proposed rule are either editorial or 
procedural in nature. These types of proposed revisions would not add 
any new requirements or impose costs. However, 38 sections of the 
proposed changes to part 36 entail changes, which warranted further 
evaluation to determine whether they involve changes in criteria or 
could impose additional costs. The key factor in evaluating the 
proposed changes in criteria was assessing whether an applicant could 
pass the noise certification test under the proposed change but fail 
the test under the current rule or vice versa, indicating a change in 
the stringency of the existing standard.
    Eight sections that would be removed by the proposed rule warranted 
further evaluation. These include sections that had previously been 
eliminated by an earlier amendment but the text had erroneously 
remained in part 36, as well as sections that are no longer relevant 
given improvements in test equipment and the enhancement of data 
correction procedures since the time part 36 was originally 
promulgated. The deletion of these sections has no cost impact.
    The FAA evaluated the remaining items to determine whether costs 
would be incurred and examined the magnitude of the cost. The sections 
of the proposed rule with potential cost fall into four categories: (1) 
Software costs, (2) additional testing procedures, (3) additional or 
new measuring provisions, and (4) additional reporting requirements.
    Software Costs--Five proposed provisions address the maintenance of 
the computer programs used to correct as-measured noise certification 
data to 14 CFR part 36 reference conditions. Such maintenance often 
times involves administrative cost. However, based on discussions with 
staff at the Volpe National Transportation Center, which work under 
contract to the FAA and evaluate certification software, the FAA has 
determined that four of these proposed changes would have no cost 
impact. The fifth, Section A36.3.7.6, would deal with technical 
differences in the ``readout'' time of the time-weighted measurement of 
the sound pressure level between the test data and the reference data. 
Implementation of this change would require modifying the computer 
software used by the applicants. The estimated times required for each 
applicant to

[[Page 42806]]

implement the software change and for the FAA to verify correct 
implementation the change are 40 and 20 hours, respectively at hourly 
wage rates of $85 and $75, respectively. The FAA estimates that 39 
applicants would incur this one-time cost, and that these software 
costs would be incurred in the first 3 years after the proposed rule's 
implementation. The total cost to industry and the FAA are $132,600 and 
$58,500 ($116,000 and $51,200 discounted), respectively.
    Testing Costs--Three proposed changes relate to the operating 
specifications of test aircraft, but none have any cost impacts.
    Measurement Costs--The FAA has determined that of the ten proposed 
changes that could affect the allowable test conditions and correction 
of test results to reference conditions, only one would have a cost 
impact. Under the proposed changes to Appendix B36.4(b), a special 
requirement would be added for propeller-driven airplanes that would 
require the placement of symmetrical 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. 
Changing part 36 would not result in increased costs for most 
applicants. However, an applicant choosing to use multiple pairs of 
microphones could incur additional costs ranging up to an estimated 
$28,000 per test. These costs would involve an increase in the number 
of microphone systems, including cable, calibration, site surveys, and 
data recording, analysis and reporting. The FAA has calculated costs 
assuming that two domestic large-propeller applicants would conduct 4 
tests meeting this requirement over the next 10 years. The total cost 
would be $112,000, or $79,200, discounted.
    Reporting Costs--Section A36.5.2 would require applicants to 
include test results in their noise certification compliance report. 
While part 36 currently does not specifically require applicants to 
submit a compliance report it is a standard practice for applicants to 
do so, since applicants already address these data elements under JAR 
36 or ICAO Annex 16. The addition of this provision would codify 
industry practice. Since the information is already provided, the FAA 
does not believe there will be additional costs to comply with this 
requirement. The FAA requests comments on this assumption and requests 
that all comments be accompanied by clear documentation supporting any 
proposed changes.
    The FAA has determined that one proposed change, to section 
A36.5.2.3, would add new data elements to the required test report. 
There would be five new elements. All of these are test airplane 
operating configuration items that could effect the airplanes noise 
signature and are already a part of the international standard. 
Additional labor costs for documenting data not previously reported are 
estimated to range from $500 (5 hours  x  $100 per hour) to $2,000 (25 
hours  x  $80 per hour) per test. These estimates are based on the 
number of additional items to be reported and on the assumption of a 
lower and upper range of required labor hour increases of 5 to 8 hours 
and 20 to 25 hours, respectively, at hourly labor rates that range from 
$80 to $100 per hour.
    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 which already comply with these 
proposed reporting requirements under JAR 36 or ICAO Annex 16 and thus 
would not incur additional reporting costs. Ten projects are conducted 
from among 24 domestic firms engaged in flight-testing and the FAA 
estimates that these firms would conduct 100 tests over the next 10 
years. The FAA further estimates that some domestic firms will incur 
additional reporting costs of $1,250 per test based on the midpoint of 
the estimated additional labor costs. 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. Since 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 would incur the 
additional reporting costs of $1,250 each, or a total of $12,500. The 
FAA estimates that of the 60 tests to be conducted by smaller domestic 
firms 24 tests would incur the additional reporting costs of $1,250 per 
test or a total of $30,000 over the next 10 years. Thus, the additional 
labor costs for reporting the additional information would total 
$42,500 ($30,000 plus $12,500) for these affected firms.
    However, it is possible that some applicants might accrue 
additional costs. If an applicant was required to invest in new 
instrumentation or data recording equipment to comply with these 
requirements, the estimated total reporting costs could increase to 
between $5,000 and $10,000 per test. This is based on a range of 
estimates and scenarios involving purchasing and installing additional 
instrumentation, and labor for adding recording capability, data 
analysis, etc. For example, one possible scenario would entail the 
purchase and installation of instrumentation hardware at $4,200 ($2,500 
for hardware and $1,700 for labor [20 hours  x  $85 per hour]), plus 
the labor cost for adding recording capability and data recording/
analysis at $3,400 (40 hours  x  $85 per hour) for a total of $7,600 of 
additional cost. The FAA estimates that only three firms would incur 
this additional cost of $7,600 per test and that these firms would 
conduct a total of 12 tests over the next 10 years at a total cost of 
$91,200. Thus, the total additional reporting costs to the industry 
would be $133,700, or $93,900 discounted, based on the minimal 
additional reporting costs of $42,500 incurred by some firms and 
$91,200 incurred by the three firms requiring additional 
instrumentation/data recording.

Summary of Costs

    The total costs for this proposed rule are $436,800, or $340,300 
discounted. Of this total, industry costs are $378,300, or $289,100 
discounted, and FAA costs are $58,500, or $51,200 discounted. Comments 
are invited on these additional cost elements; the FAA requests that 
all comments be accompanied by clear economic documentation.

Cost Savings

    Several of the proposed changes could result in cost savings to 
applicants, depending upon the current inventory of the applicant's 
test equipment and the particular weather circumstances of the flight 
test. However, given the uncertainty in the annual number and duration 
of flight tests, it is difficult to accurately quantify these savings. 
For example, Section A36.2.2.2(b) would lower the minimum test 
temperature from 36 degrees Fahrenheit to 14 degrees Fahrenheit. This 
proposed change is based on technical data from extensive noise testing 
experience and is within the operational temperature limit of the noise 
measuring equipment. One of the largest cost elements of the test 
certification process is the cost associated with airplane down time; 
by extending the temperature range, down time could 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

[[Page 42807]]

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 warming patterns that could result in reduced hours of 
airplane down time, an applicant might reduce 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 $150,000 to $200,000 per 
day for larger planes and $70,000 to $140,000 per day for smaller 
airplanes, cost reductions per test made possible by this change in 
minimum test temperatures could range between approximately $75,000 and 
$200,000 for larger airplanes and manufacturers and between $35,000 and 
$140,000 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 not 
encounter this situation during a 10 year period.
    The FAA estimates that 24 larger applicants would each derive cost 
savings of $137,500 per test and 13 smaller firms would save $87,500 
each per test. The estimated industry cost savings over ten years 
totals $4.44 million, or $3.12 million discounted. Comments on these 
estimates are invited; the FAA requests that all comments be 
accompanied by clear documentation supporting any proposed changes.
    Proposed 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 would allow the 
full power noise measurement to be obtained at a point (650m) below the 
takeoff flight path and thus eliminate the problems associated with 
obtaining this measurement from the conventional sideline site. 
According to industry sources, 40 to 45 fly-bys per test could be 
eliminated and between 2 and 8 microphone systems could be eliminated 
depending on the size of the array used by the applicant. (Many 
applicants currently use a 2-microphone sideline array.) In addition to 
the significant savings resulting from the reduction in the number of 
fly-bys and the number of microphone systems, further cost savings 
could 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 at $200,000 to $350,000 per test for manufacturers of 
propeller-driven large planes. These estimates are based on a range of 
potential scenarios involving combinations of the above elements (the 
number of fly-bys and the number of microphones used, flight test 
costs, etc.). As an example, based on a reduction of 42 fly-bys, the 
midpoint of the estimated range, and an example cost factor of $6,000 
per fly-by, cost savings of $252,000 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 
$7,000 per system, another $28,000 (4 systems  x  $7,000 per system) in 
savings would be realized, for a total example savings of $280,000 per 
test under this example. Given the increasing demand for regional jets, 
and the financial status of large propeller-driven manufacturers, the 
FAA estimates that no more than 10 tests would be conducted over the 
next 10 years and that the derived cost savings would total $2.80 
million or $1.97 million discounted.
    Industry sources estimate that cost savings on the order of $37,500 
per year for those applicants with considerable certification activity 
would be realized by the harmonization of testing, data measurement and 
analysis, reporting and documentation. Industry sources also claim that 
these cost savings would be achieved by a reduction in the confusion 
and the multiple interpretations that lead to delays, duplicate effort 
and costly negotiation caused by the existing dual certification 
standards. The FAA estimates that 10 firms engaged in noise 
certification activities would achieve cost savings of $375,000 
annually for the industry. The estimated industry cost savings over ten 
years totals $3.75 million, or $2.63 million discounted.
    Total quantifiable cost savings over ten years would be $10.99 
million, or $7.72 million discounted. The FAA has not been able to 
quantify other potential savings made possible by the greater 
efficiencies and flexibility resulting from the uniformity that the 
proposed rule would provide. Comments are invited; the FAA requests 
that all comments be accompanied by clear documentation. The FAA would 
particularly appreciate specific cost savings data.

Benefits

    Currently, airplane manufacturers must satisfy both the FAA and the 
European noise certification standards in order to market their 
aircraft in both the United States and Europe. Meeting two sets of 
noise certification requirements raises the cost of developing a new 
transport category airplane, often with no increase in safety or 
environmental benefit. Adoption of these proposed changes to the noise 
certification standards of part 36 will foster international trade, 
lower the cost of aircraft development, and make the certification 
process more efficient.

Cost-Benefit Analysis

    If the proposed rule becomes effective, U.S. noise certification 
procedures would 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 
would result in significant cost savings without compromising the 
environmental benefits of the noise certification standards.
    The proposed rule's cost savings, over ten years (attributable to 
specific proposed changes to part 36 and achieving near uniformity of 
the standards), would be $7.24 million, $5.08 million discounted. In 
addition, $3.75 million, $2.63 million discounted, would be derived 
from overall efficiencies attributable to the harmonization effort in 
achieving near uniformity of the FAA and JAA standards for a total 
savings of $10.99 million, $7.72 million, discounted which exceeds the 
proposed rule's cost of $436,800 ($340,300, discounted). Since the 
potential cost savings exceed the additional costs, the proposed rule 
would be cost beneficial.

Initial Regulatory Flexibility Act

    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 
rational for their actions. Agencies must perform a review to determine 
whether a proposed or

[[Page 42808]]

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 1980 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.
    Enactment of this proposal would impose costs of $436,800 on the 
FAA and noise certification applicants over the ten year period of 
which $250,400 would be incurred by smaller applicants. The FAA has 
assumed that two smaller applicants which is not a substantial number 
of applicants would each incur measurement costs of $56,000, or a total 
of $112,000. Additional reporting costs requiring additional 
instrumentation/data recording totaling $60,800 over the ten year 
period would be incurred by 2 other smaller applicants or $30,400 each. 
Additional labor costs for new reporting requirements totaling $30,000 
over the 10 year period would be incurred by 6 smaller applicants at a 
cost to each of these smaller applicants over the 10 year period of 
$5,000.
    All the small (14) applicants at a cost of $3,400 each or a total 
of $47,600 would incur one time software costs and for four of these 
firms this would be the only cost they incur. The first-year cost to 
each of the six small applicants incurring both software and additional 
labor reporting costs would be $4,650. In this case, the FAA has 
determined this would not be a significant cost to a substantial number 
of small noise certification applicants. Therefore, the FAA had 
determined that this proposed rule would 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 activity 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 appropriate, that they be the basis for U.S. 
standards. In addition, consistent with the Administration's belief in 
the general superiority and desirability of free trade, it is the 
policy of the Administration to remove or diminish, to the extent 
feasible, barriers to international trade, including both barriers 
affecting the export of American goods and services to foreign 
countries and barriers affecting the import of foreign goods and 
services into the U.S.
    In accordance with the above statute and policy, the FAA has 
assessed the potential effect of this proposed rule and has determined 
that it will impose the same costs on domestic and international 
entities and thus has a neutral trade impact.

Executive Order 13132, Federalism

    The FAA has analyzed this proposed rule under the principles and 
criteria of Executive Order 13132, Federalism. The FAA has determined 
that this action would not have substantial direct effects on the 
States, on the relationship between the national Government and the 
States, or on the distribution of power and responsibilities among the 
various levels of government. Therefore, the FAA has determined that 
this notice of proposed rulemaking would not have federalism 
implications.

Unfunded Mandates

    The Unfunded Mandates reform Act of 1995 (2 U.S.C. 1532-1538) 
requires the FAA to assess the effects of Federal Regulatory actions on 
state, local, and tribal governments, and on the private sector of 
proposed rules that contain a Federal intergovernmental or private 
sector mandate that exceeds $100 million in any one year. This action 
does not contain such a mandate.

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 proposes that this 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 notice 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 notice is not a major regulatory action under the provisions 
of the EPCA.

List of Subjects in 14 CFR Part 21 and 36

    Aircraft, Noise control.

The Proposed Amendment

    In consideration of the foregoing the Federal Aviation 
Administration proposes to amend 14 CFR parts 21 and 36, as follows:

PART 21--CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS

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

    Authority: 42 U.S.C. 7572; 49 U.S.C. 106(g), 40105, 40113, 
44701-44702, 44707, 44709, 44711, 44713, 44715, 45303.


Sec. 21.17  [Amended]

    2. Amend paragraph (a) of Sec. 21.17 by removing the word ``parts'' 
and adding the word ``part'' and removing the words ``and 36''.


Sec. 21.101  [Amended]

    3. Amend paragraph (a) of Sec. 21.101 by removing the word 
``parts'' and adding the word ``part'' and removing the words ``and 
36''.

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

    1. 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. 11514, 35 FR 4247, 3 CFR, 1966-1970 Comp., p. 902.


Sec. 36.1  [Amended]

    2. 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 (d), introductory text, remove the words ``turbojet 
powered'' and add the word ``jet'' in its place.
    c. Remove paragraph (d)(3).
    d. In paragraph (f) remove the words ``turbojet powered'' and 
insert 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 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)(3) remove the reference to ``C36.5(a)(2)'' and 
add ``B36.5(b)'' in its place and remove the

[[Page 42809]]

reference to ``C36.5(a)(3)'' and insert ``B36.5(c)'' in its place;
    g. In paragraph (f)(4) remove the reference to ``C36.5'' and add 
``B36.5(b)'' in its place;
    h. In paragraph (f)(5) remove the reference to ``C36.5(a)(3)'' and 
add ``B36.5(c)'' in its place;
    i. In paragraph (f)(6) remove the reference to ``C36.5'' and add 
``B36.5(c)'' in its place; and.
    j. In paragraph (g) remove the word ``turbojet'' and add the word 
``jet'' in its place.


Sec. 36.2  [Removed and reserved]

    3. Remove and reserve Sec. 36.2.


Sec. 36.6  [Amended]

* * * * *
    4. Amend Sec. 36.6 as follows:
    a. Add paragraphs (c)(1)(vi) through (x);
    b. Revise paragraphs (d)(1)(i) and (ii), (e)(3)(ii), (e)(3)(vii), 
and (e)(3)(ix).
    The additions and revisions read as follows:
    (c) * * *
    (1) * * *
    (vi) 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 Noise-Performance Requirements for Systems to 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]

    5. Amend Sec. 36.7 to read as follows:
    a. 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 B'' in its place.
    c. In paragraph (b)(2) remove the reference to ``C36.9'' and add 
``B36.8'' in its place.
    d. In paragraph (c)(1) remove the reference to ``C36.5(b)'' and add 
``B36.6'' in its place.
    e. In paragraph (d)(1) remove the word ``turbojet'' and add the 
word ``jet'' in its place.
    f. In paragraph (d)(1)(ii) remove the reference to ``C36.5(b)'' and 
add ``B36.6'' in its place.
    g. In paragraph (d)(2) remove the word ``turbojet'' and add the 
word ``jet'' in its place.

Subpart B--Transport Category Large Airplanes and Jet Airplanes

    6. Revise the heading of Subpart B to read as set forth above.
    7. Revise Sec. 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.
    8. Revise Sec. 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 
flight test conditions under section C36.8 (or an approved equivalent 
procedure), stated under appendix C 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.


Sec. 36.201 (Subpart C)  [Removed]

    9. Remove and reserve subpart C, consisting of Sec. 36.201.


Sec. 36.1581  [Amended]

    10. Amend Sec. 36.1581(a)(1) and (d) by removing the words 
``turbojet powered'' and adding the word ``jet'' in its place.
    11. 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 states the 
measurement procedures that must be used to measure airplane noise 
during each test conducted on or after [insert effective date of 
final rule]. 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 airplane 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 sections A36.6 to A36.9 of 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 resultant changes in noise can often 
be established reliably without the necessity of resorting to a 
complete test as outlined in this appendix. For this reason the FAA 
permits the use of appropriate ``equivalent procedures''. There are 
also equivalent procedures that may be used in full certification 
tests, in the interest of

[[Page 42810]]

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 
operated within their 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;
    (d) If the atmospheric absorption coefficients vary over the 
PNLTM sound propagation path by more than 1.6dB/1000ft 
(0.5dB/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 10 meters above ground is not to 
exceed 12 knots and the crosswind velocity for the airplane is not 
to exceed 7 knots. The average wind velocity must be determined 
using a thirty-second averaging period spanning the 10 dB down time 
interval. 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.
    (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(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 
approved 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 this section 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.
    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 mean 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.


[[Page 42811]]


    Note: The free-field sensitivity level of a microphone system 
may be determined by subtracting the sound pressure level (in 
decibels re 20 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 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 angle 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 use instruments that 
conform to the specifications of this section 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, the 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 conform to the 
specifications in sections A36.3.5.2 to A36.3.5.4. Various 
microphone systems may be approved by the FAA on the basis 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. This demonstration of equivalent performance does not 
eliminate the need to calibrate and check each system as defined 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

[[Page 42812]]

Table A36-1 must not exceed the tolerance limit for the greater 
angle.
[GRAPHIC] [TIFF OMITTED] TP11JY00.009


 Maximum Difference Between the Free-Field Sensitivity Level of a Microphone System at Normal Incidence and the
                        Free-Field Sensitivity Level at Specified Sound Incidence Angles
----------------------------------------------------------------------------------------------------------------
                                                         dB Sound incidence angle degrees
  Nominal midband frequency kHz  -------------------------------------------------------------------------------
                                        30              60              90              120             150
----------------------------------------------------------------------------------------------------------------
0.05 to 1.6.....................             0.5             0.5             1.0             1.0             1.0
2.0.............................             0.5             0.5             1.0             1.0             1.0
2.5.............................             0.5             0.5             1.0             1.5             1.5
3.15............................             0.5             1.0             1.5             2.0             2.0
4.0.............................             0.5             1.0             2.0             2.5             2.5
5.0.............................             0.5             1.5             2.5             3.0             3.0
6.3.............................             1.0             2.0             3.0             4.0             4.0
8.0.............................             1.5             2.5             4.0             5.5             5.5
10.0............................             2.0             3.5             5.5             6.5             7.5
----------------------------------------------------------------------------------------------------------------

Table A36-1  Microphone Directional Response Requirements

    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 a way that a record of the complete 
acoustical signal is retained. The recording and reproducing systems 
must conform to 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 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

[[Page 42813]]

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 reference level range, the level corresponding 
to 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.
    A36.3.7  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: Tests of the one-third octave band analysis system may be 
made according to the methods described in IEC 61260 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 1 s after interruption. The rising response must 
be -4  1 dB at 0.5 s, -1.75  0.75 dB at 1 s, 
-1  0.5 dB at 1.5 s and -0.5  0.5 dB at 2 s 
relative to the steady-state level. The falling 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 1 s. At 
subsequent times the sum of the rising and falling responses must be 
-7.5 dB or less. This equates to an exponential averaging process 
(slow weighting) with a nominal 1 s time constant (i.e., 2 s 
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 weighted sound pressure levels can be 
obtained using a continuous exponential averaging process by the 
following equation:

Ls(i,k) = 10 log [(0.60653)10 \0.1Ls[i,(k-1)]\ + 
(0.39347) 10 \0.1 L(i,k)]\

Where Ls(i,k) is the simulated slow weighted sound 
pressure level and L(i,k) is the as-measured 0.5 s 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. For k 
=1, the slow 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 ( 4:

Ls(i,k) = 10 log [(0.13)10 \0.1L[i,(k-3)]\ + (0.21) 10 
\0.1L[i,(k-2)]\ +(0.27) 10 \0.1L[i,(k-1)]\ + (0.39)10 \0.1L[i,k]]\
Where Ls(i,k) is the simulated slow weighted sound 
pressure level and L(i,k) is the as measured 0.5 s 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 0.5 s data samples, or for times 
greater than 2.5 s after initiation of data analysis.

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

    A36.3.7.6 The instant in time by which a slow time weighted 
sound pressure level is characterized must be 0.75 s earlier than 
the actual readout time.

    Note: The definition of this instant in time is required to 
correlate the recorded noise with the aircraft position when the 
noise was emitted and takes into account the averaging period of the 
slow 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

[[Page 42814]]

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 grazing 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 end. Data obtained from 
analogue 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. The output of the noise generator 
must 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 within six months of 
each test series. Any 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 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 known at the prevailing environmental 
conditions corresponding with each test series. The difference 
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 not 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.
    A36.3.9.11  Ambient noise, including both 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.
    A36.3.9.12  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 A36.3.9.11 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. Simply 
stated, 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

[[Page 42815]]

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 one of the methods of 
sub-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, or to the Table of Perceived Noisiness in the current 
Advisory Circular for this part.
    (b) Step 2: Combine the perceived noisiness values, n(i,k), 
determined in step 1 by using the following formula:
[GRAPHIC] [TIFF OMITTED] TP11JY00.000

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] TP11JY00.001


    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 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:

|s(i,k)| = |s(i,k)-s(i-1,k)|>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) Step 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 42816]]

[GRAPHIC] [TIFF OMITTED] TP11JY00.010

    (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) values 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 it has occurred that 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 42817]]


[GRAPHIC] [TIFF OMITTED] TP11JY00.011

    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 identify 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] TP11JY00.007

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] TP11JY00.008

Where 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 t; or
    (b) A shorter time interval with approved limits and constants.
    A36.4.5.4 The following values for T and t must be used 
in calculating D in the equation given in section A36.4.5.2:
T = 10 s, and
t = 0.5 s (or the approved sampling time interval).
Using these values, the equation for D becomes:

[[Page 42818]]

[GRAPHIC] [TIFF OMITTED] TP11JY00.006

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.
    A36.4.6.1-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  SPL(a)
n = antilog {M(c)[SPL - SPL(c)]}
(b)
SPL(b)  SPL  SPL(a)
n = antilog {M(b)[SPL - SPL(b)]}
(c)
SPL(e)SPL SPL(b)
n = 0.3antilog {M(e)[SPL - SPL(e)]}
(d)
SPL(d)SPL SPL(e)
n = 0.1 antilog {M(d)[SPL - SPL(d)]}

    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.

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. In particular, the corrections to measurements for 
equipment response deviations must be reported.
[GRAPHIC] [TIFF OMITTED] TP11JY00.012


[[Page 42819]]


    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.
    The following must be reported to the FAA in the applicant's 
noise certification compliance report.
    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.
[GRAPHIC] [TIFF OMITTED] TP11JY00.013

    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;

[[Page 42820]]

    (d) Airplane configuration such as flap, airbrakes and landing 
gear positions and propeller pitch angles (if applicable) for each 
test run;
    (e) Whether auxiliary power units (APU), when fitted, are 
operating for each test run;
    (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. Any such modifications or non-
standard equipment must be approved by the FAA.
    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 C 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 per 
cent 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 per cent 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 per cent confidence limit not exceeding 
1.5 EPNdB. No test result may be omitted from the 
averaging process unless approved by the FAA.

    Note: Methods available for calculating the 90 per cent 
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).
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....................................  per cent...............  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 any instant of time
                                                                 that occurs in a specified frequency range.
n(i,k)...............................  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).
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).

[[Page 42821]]

 
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)
                                                                 is obtained by adjusting the value of PNL(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.
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 20 Pa...  Sound pressure level. The sound pressure level
                                                                 that occurs in a specified frequency range at
                                                                 any instant of time.
SPL(a)...............................  dB re 20 Pa...  Noy discontinuity coordinate. The SPL value of
                                                                 the intersection point of the straight lines
                                                                 representing the variation of SPL with log n.
SPL(b) SPL(c)........................  dB re 20 Pa...  Noy intercept. The intercepts on the SPL-axis of
                                                                 the straight lines representing the variation
                                                                 of SPL with log n.
SPL(i,k).............................  dB re 20Pa....  The sound pressure level at the k-th instant of
                                                                 time that occurs in the i-th one-third octave
                                                                 band.
SPL'(i,k)............................  dB re 20Pa....  Adjusted sound 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 20Pa....  Maximum sound 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 20Pa....  Corrected maximum 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 20Pa....  Final background 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.
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.
(i).........................  dB/1000ft dB/100m......  Test 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.
(i)o........................  dB/1000ft dB/100m......  Reference atmospheric absorption. The
                                                                 atmospheric attenuation of sound that occurs in
                                                                 the i-th one-third octave band at a reference
                                                                 air temperature and relative humidity.
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)
 , ................  degrees................  Thrust cutback angles. The angles defining the
                                                                 points on the takeoff flight path at which
                                                                 thrust reduction is started and ended
                                                                 respectively.
...........................  degrees................  Approach angle.
r..........................  degrees................  Reference approach angle.
...........................  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.
...........................  degrees................  Noise angle (relative to ground). The angle
                                                                 between the noise paths and the grounds. It is
                                                                 identical for both measured and corrected
                                                                 flight paths.
............................  .......................  Engine noise emission parameter.
r...........................  .......................  Reference engine noise emission parameter.
 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.
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.
 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] TP11JY00.002
    
and

[[Page 42822]]

[GRAPHIC] [TIFF OMITTED] TP11JY00.003

Where

() is listed in Table A36-4 and f0 in 
Table A36-5;
(i) is the attenuation coefficient in dB/1000 ft;
 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] TP11JY00.004

and
[GRAPHIC] [TIFF OMITTED] TP11JY00.005

Where

() is listed in Table A36-4 and f0 in 
Table A36-5;
(i) is the attenuation coefficient in dB/100 m;
 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]

              Table A36-4.--Values of ()
------------------------------------------------------------------------
     ()       ()
------------------------------------------------------------------------
      0.00              0.000              2.50             0.450
      0.25              0.315              2.80             0.400
      0.50              0.700              3.00             0.370
      0.60              0.840              3.30             0.330
      0.70              0.930              3.60             0.300
      0.80              0.975              4.15             0.260
      0.90              0.996              4.45             0.245
      1.00              1.000              4.80             0.230
      1.10              0.970              5.25             0.220
      1.20              0.900              5.70             0.210
      1.30              0.840              6.05             0.205
      1.50              0.750              6.50             0.200
      1.70              0.670              7.00             0.200
      2.00              0.570             10.00             0.200
      2.30              0.495         ..........  ......................
------------------------------------------------------------------------


                       Table A36-5.--Values of f0
------------------------------------------------------------------------
 One-third octave                     One-third octave
 center frequency       f0 (Hz)       center frequency       f0 (Hz)
------------------------------------------------------------------------
           50                50                800               800
           63                63               1000              1000
           80                80               1250              1250
          100               100               1600              1600
          125               125               2000              2000
          160               160               2500              2500
          200               200               3150              3150
          250               250               4000              4000
          315               315               5000              4500
          400               400               6300              5600
          500               500               8000              7100
          630               630              10000              9000
------------------------------------------------------------------------

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 quantify 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:
    (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

[[Page 42823]]

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.
    The airplane reference point for approach measurements is the 
instrument landing system (ILS) antenna.

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    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

[[Page 42825]]

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 portions of the test flight path and the reference 
flight path described below, and illustrated in Figure A36-6, 
include the 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.
[GRAPHIC] [TIFF OMITTED] TP11JY00.015

    (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 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 paragraphs (b)(1) and (2) of this section 
below, 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 A36-7(b), 
XrYr represents the corresponding portion of 
the reference flight path. 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 .
    (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 assumptions that QK and 
QrKr:
    (i) Form the same angle  with their respective flight 
paths; and
    (ii) Form the same angle  with the ground.

[[Page 42826]]

[GRAPHIC] [TIFF OMITTED] TP11JY00.016

    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[(i)-
(i)o]QK
+ 0.001(i)o (QK - QrKr
+ 20log(QK/QrKr)

    In this expression,
    (1) The term 0.001[(i)-(i)o]QK is 
the adjustment for the effect of the change in sound attenuation 
coefficient, and (i) and (i)o are the 
coefficients for the test and reference atmospheric conditions 
respectively, determined under section A36.7 of this appendix;
    (2) The term 0.001(i)o(QK-
QrKr) is the adjustment for the effect of the 
change in the noise path length on the sound attenuation;
    (3) The term 20log(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 
(i) and (i)o 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[(i)-
(i)o]QK
+ 0.01(i)o (QK - QrKr
+ 20log(QK/QrKr)

    In this expression,
    (1) The term 0.01[(i)-(i)o]QK is 
the adjustment for the effect of the change in sound attenuation 
coefficient, and (i) and (i)o are the 
coefficients for the test and reference atmospheric conditions 
respectively, determined under section A36.7 of this appendix;
    (2) The term 0.01(i)o (QK-
QrKr is the adjustment for the effect of the 
change in the noise path length on the sound attenuation;
    (3) The term 20log(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 
(i) and (i)o 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 using the following equation:

1 = PNLTr - PNLTM

    A36.9.3.2.1.2  Add 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

[[Page 42827]]

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

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

    (a) Add 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 , 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 r are required to calculate 
the source noise adjustments for lateral, flyover and approach noise 
measurements.
[GRAPHIC] [TIFF OMITTED] TP11JY00.017

    A36.9.3.4.2  Calculate adjustment term 3 by 
subtracting the EPNL value corresponding to the parameter  
from the EPNL value corresponding to the parameter 
r. Add 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.
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[[Page 42828]]


    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) of this section, 
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:
[GRAPHIC] [TIFF OMITTED] TP11JY00.019

    (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 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 
(01 with their respective flight paths. 
Qr 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 paragraphs (b)(1) and (2) of this section, 
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. 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 .
    (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. 
Q0 and Qn are chosen so 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 position of Kr and Qr1 are 
determined from the following requirements:
    (A) Q1K and Qr1Kr form the same 
angle 1 with their respective flight paths; and
    (B) 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)(A) is met while at the same time keeping 
1 and r1 equal.
    A36.9.4.2.1  In paragraphs A36.9.4.2(a)(2) and (b)(2) the time 
tr1 is

[[Page 42829]]

later (for Qr1Kr > Q1K) than 
t1 by two 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 1: For the flight paths described in paragraphs 
A36.9.4.2(a) and (b), if thrust or power cut-back is used there will 
be test and reference flight paths at full thrust or power and at 
cut-back thrust or power. Where the transient region between these 
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, 3, 
must be determined using the methods of section A36.9.3.4 of this 
appendix.
    A36.9.5  Flight path identification positions.

------------------------------------------------------------------------
             Position                            Description
------------------------------------------------------------------------
A.................................  Start of Takeoff roll.
B.................................  Lift-off.
C.................................  Start of first constant climb.
D.................................  Start of thrust 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
                                     B36.9.3.2.
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.
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.
----------------------------------------------------------------------------------------------------------------


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[[Page 42831]]


    12. 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.
B36.5  Maximum noise levels.
B36.6  Trade-offs.
B36.7  Noise certification reference procedures.
B36.8  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 and 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).
    (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 March 20, 2002, 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 (6,500m) 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 obtain 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; 
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

    (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.
    (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; and
    (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 
start 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).

[[Page 42832]]

    (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 March 20, 2002, a single reference flight 
path that includes thrust cutback in accordance with paragraph 
(b)(1) 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 Concorde 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 engine 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 point. 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 10dB-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 10dB-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.
    13. Remove and reserve appendix C of part 36.

Section G36.105  [Amended]

    14. Amend paragraph (f) of section G36.105 of appendix G by 
removing the reference ``paragraph A36.3(e) of Appendix A'' and 
adding ``paragraphs A36.3.8 and A36.3.9 of Appendix A'' in its 
place.

Section H36.111  [Amended]

    15. Amend paragraph (c)(3) of section H36.111 of appendix H by 
removing the reference ``A36.3(f)(3)'' and adding ``A36.3.9.11'' in 
its place.

Section H36.201  [Amended]

    16. Amended paragraph (b) of section H36.201 of appendix H by 
removing the reference ``B36.5(a)'' and adding ``A36.4.3.1--Step 1'' 
in its place.

    Issued in Washington, DC, on June 29, 2000.
Paul R. Dykeman,
Acting Director of Environment and Energy.
[FR Doc. 00-16913 Filed 7-10-00; 8:45 am]
BILLING CODE 4910-13-P