[Federal Register Volume 63, Number 222 (Wednesday, November 18, 1998)]
[Proposed Rules]
[Pages 64146-64151]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-30578]



[[Page 64145]]

_______________________________________________________________________

Part II





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



_______________________________________________________________________



14 CFR Part 36



Noise Certification Standards for Propeller-Driven Small Airplanes; 
Proposed Rule

  Federal Register / Vol. 63, No. 222 / Wednesday, November 18, 1998 / 
Proposed Rules  

[[Page 64146]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 36

[Docket No. FAA-1998-4731; Notice No. 98-16]
RIN 2120-AG65


Noise Certification Standards for Propeller-Driven Small 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of Proposed Rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA is proposing changes to the noise certification 
standards for propeller-driven small airplanes. These proposals 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 
propeller-driven small airplanes. These proposed changes would provide 
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 January 19, 1999.

ADDRESSES: Comments on this proposed rulemaking should be mailed or 
delivered, in duplicate, to: U.S. Department of Transportation Dockets, 
Docket No. FAA-1998-4731, 400 Seventh Street, SW., Room Plaza 401, 
Washington, DC 20590. Comments may also be sent electronically to the 
following Internet address: [email protected]. Comments may be 
filed and/or examined in Room Plaza 401 between 10 a.m. and 5 p.m. 
weekdays except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Mehmet Marsan, Office of Environment 
and Energy (AEE), Federal Aviation Administration, 800 Independence 
Avenue, SW., Washington, DC 20591; telephone (202) 267-7703.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Comments relating to the environmental, energy, 
federalism, or economic impact that might result from adopting the 
proposals in this notice are also invited. Substantive comments should 
be accompanied by cost estimates. Comments must identify the regulatory 
docket or notice number and be submitted in triplicate to the Rules 
Docket address specified above.
    All comments received, as well as a report summarizing each 
substantive public contact with FAA personnel on this rulemaking, will 
be filed in the docket. The docket is available for public inspection 
before and after the comment closing date.
    All comments received on or before the closing date will be 
considered by the Administrator before taking action on this proposed 
rulemaking. Late-filed comments will be considered to the extent 
practicable. The proposals contained in this notice may be changed in 
light of the comments received. Commenters wishing the FAA to 
acknowledge receipt of their comments submitted in response to this 
notice must include a pre-addressed, stamped postcard with those 
comments on which the following statement is made: ``Comments to Docket 
No. FAA-1998-4731.'' The postcard will be date stamped and mailed to 
the commenter.

Availability of the NPRM

    An electronic copy of this document can 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), the Government Printing Office's electronic bulletin board 
service (telephone: 202-512-1661).
    Internet users may reach the FAA's web page at http://www.faa.gov 
or the Government Printing Office's webpage at http://
www.access.gpo.gov/nara for access to recently published rulemaking 
documents.
    Any person may obtain a copy of this NPRM by mail by submitting a 
request to the Federal Aviation Administration, Office of Rulemaking, 
800 Independence Avenue, SW., Washington, DC 20591, or by calling (202) 
267-9677. Communications must identify the notice number of this NPRM.
    Persons interested in being placed on the mailing list for future 
NPRM's should request from the FAA's Office of Rulemaking a copy of 
Advisory Circular No. 11-2A, Notice of Proposed Rulemaking Distribution 
System, that 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 contains the FAA's noise standards and regulations 
that apply to the issuance of type certificates for all types of 
aircraft. The standards and requirements that apply to propeller-driven 
small airplanes and propeller-driven commuter category airplanes are 
found in Sec. 36.501 and Appendix G of Part 36. Appendix G addresses 
Takeoff Noise Requirements for propeller-driven small airplane and 
propeller-driven commuter category airplane Certification Tests on or 
after December 22, 1988. This appendix was added to part 36 in 1988 to 
require actual takeoff noise tests instead of the level flyover test 
that was formerly required under Appendix F, for airplanes for which 
certification tests were completed before December 22, 1988.
    Appendix G specifies the test conditions, procedures, and noise 
levels necessary to demonstrate compliance with certification 
requirements for propeller driven small airplanes and propeller-driven, 
commuter category airplanes.

Government and Industry Cooperation

    In June 1990 there was a meeting of the Joint Aviation Authorities 
(JAA) Council, which consists of JAA members from European countries, 
and the FAA. The FAA Administrator committed FAA to support the 
harmonization of the FAA 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 announced the renewal of ARAC on February 19, 1993 (58 FR 9230) 
and on March 1, 1995 (60 FR 11165). One area that ARAC deals with is 
noise certification issues. These issues involve the harmonization of 
14 CFR part 36 (part 36) with JAR part 36, the associated guidance 
material including equivalent procedures, and the interpretation of the 
regulations. On May 3, 1994, the ARAC established the FAR/JAR 
Harmonization Working Group for Propeller-Driven Small Airplanes (59 FR 
22885). The Working Group was tasked with reviewing the applicable 
provisions of subparts A and F, and appendices F and

[[Page 64147]]

G of part 36, and harmonizing them with the corresponding applicable 
provisions 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. The Working Group was 
also asked to recommend a process whereby subsequent ICAO Annex 16 
changes could be properly incorporated into JAR 36 and part 36.
    The Working Group reviewed 16 items related to noise limits and 
measurement procedures in the regulations. For six of these items, the 
Working Group recommended that part 36 be amended to harmonize the 
regulations with JAR 36. For four of these items, the Working Group 
recommended that JAR 36 be amended to harmonize those regulations with 
part 36. For the six remaining items, the Working Group found that no 
harmonization is necessary. The Working Group also recommended changes 
to harmonize FAA and JAA interpretive and advisory material relating to 
noise limits for propeller-driven small airplanes. This NPRM reflects 
the six recommendations that address changes to part 36.

Discussion of Proposals

    The proposed changes to appendix G would affect the provisions that 
establish noise measurement procedures (sec. G36.107), corrections to 
test results (sec. G36.201) and specific aircraft noise limits that are 
tied to aircraft weight (sec. G36.301).

Section G36.107  Noise Measurement Procedures

    Currently, section G36.107 prescribes specific procedures for the 
placement of microphones, system calibration and consideration of 
ambient noise. The proposed changes would affect the microphone 
requirements of paragraph (a). Currently, microphones are required to 
be oriented in a known direction so that the maximum sound received 
arrives as nearly as possible in the direction for which the 
microphones are calibrated, and the microphone sensing elements must be 
placed four feet (1.2 m) above ground level.
    The proposed change to section G36.107(a) would require the 
microphone to be a pressure-type microphone with a protective grid that 
is 12.7 mm in diameter. The microphone would have to be mounted in an 
inverted position so that the diaphragm is 0.7 mm above and parallel to 
a white-painted metal circular plate. The plate would have to be 40 cm 
in diameter and at least 2.5 mm thick. The plate would have to be 
placed horizontally and flush with the surrounding ground surface with 
no cavities below the plate. The microphone would have to be located 
three-quarters of the distance from the center to the edge of the plate 
along a radius normal to the line of flight of the test airplane.
    The proposed changes, which would make the U.S. regulations 
consistent with the JAR, are supported by numerous studies, technical 
papers, and discussions with interested groups. The technical data 
indicate that an inverted microphone that measures reflected noise from 
a metal plate at ground level produces more consistent and reliable 
data. A microphone that is four feet above the ground is much more 
likely to be affected by variable ground reflections that can interact 
with the noise produced by the aircraft being measured. The microphone 
height reduction and the metal plate substantially eliminate these 
variations.
    However, studies also show that measurements using the inverted 
microphone and metal plate technique produce consistently higher noise 
levels than those produced under the current procedure, with the 
difference being about 3 dB(A). Therefore, to maintain the present 
level of noise stringency, a corresponding change to section G36.301(b) 
is necessary as discussed below.

Section G36.201  Corrections to Test Results

    Current section G36.201 prescribes corrections to be made to test 
results to account for the effects of differences between the 
conditions referenced in the prescribed procedures and existing 
conditions during an actual test.
    Current section G36.201(b) requires atmospheric absorption 
correction for noise data obtained when the test conditions are outside 
those specified in appendix G, figure G1. Noise data collected outside 
the prescribed range of figure G1 are required to be corrected to 77 
degrees F and 70 percent relative humidity by an FAA approved method. 
The FAA is proposing to change the 77 degrees F reference temperature 
to 59 degrees F, to be consistent with the ambient temperature 
requirement in current section G36.111(b)(2) that is used for 
performance calculations. By making the reference temperatures 
consistent for absorption and performance, delays and confusion that 
have been caused by the inconsistency in the current rule would be 
eliminated. The change would bring part 36 in line with Annex 16.
    Current section G36.201(c) requires that helical tip Mach number 
and power corrections must be made if the propeller is a variable pitch 
type or if the propeller is a fixed pitch type and the test power is 
not within five percent of the reference power. The proposed change 
would provide an additional exception by stating that a correction is 
not necessary if the helical tip Mach number meets one of the 
following:
    1. The number is at or below 0.70 and the test helical tip Mach 
number is within 0.014 of the reference helical tip Mach number.
    2. The number is above 0.70 and at or below 0.80 and the test 
helical tip Mach number is within 0.007 of the reference helical tip 
Mach number.
    3. The number is above 0.80 and the test helical tip Mach number is 
within 0.005 of the reference helical tip Mach number. For mechanical 
tachometers, if the helical tip Mach number is above 0.8 and the test 
helical tip Mach number is within 0.008 of the reference helical tip 
Mach number.
    These additional proposed exceptions are based on an analysis of 
noise data from nine U.S.-manufactured aircraft. This analysis 
indicated that the proposed values are well within the Type 1 sound 
level meter as defined in International Electrotechnical Commission 
(IEC) Publication No. 651, which has been incorporated by reference in 
part 36. Adding this exemption would simplify some tests without 
degrading the results.
    Current section G36.201(d)(1) requires that the measured sound 
levels must be corrected from the test day meteorological conditions by 
adding an increment equal to the result gained from the following 
equation:
    Delta (M)=(-0.7) HT/1000.
    In this equation, HT is the height in feet of the test 
aircraft when directly over the noise measurement point, and  
is the rate of absorption for the test day conditions at 500 Hz as 
referenced in Society of Automotive Engineers (SAE) Publication 
Aerospace Recommended Practice (ARP) 866A which has been incorporated 
by reference in part 36.
    The equation in section G36.201(d)(1) is an approximation. The 
accuracy of the calculations can be improved by adopting the exact form 
of the equation. Therefore, the FAA proposes to change the equation to 
the exact form which reads as follows:
    Delta (M)=(HT-0.7 HR)/1000.
    In this equation HT is the height in feet under test 
conditions, HR is the height in feet under reference

[[Page 64148]]

conditions when the aircraft is directly over the noise measurement 
point, and  is the same as in the current rule, that is, the 
rate of absorption for the test day conditions at 500 Hz as specified 
in SAE ARP 866A.
    The proposed equation would bring appendix G absorption 
calculations in line with the rest of part 36 absorption calculations 
and Annex 16.
    Current section G36.201(d)(4) requires that the measured sound 
levels in decibels must be corrected for engine power by algebraically 
adding an increment equal to:
    Delta (3)=17 log (PR/PT)
where PT and PR are the test and reference engine 
powers respectively.
    The FAA proposes that the algebraic correction for engine power be 
changed to:
    Delta (3)=K3 log (PR/PT)
where PR and PT are the test and reference engine 
powers respectively obtained from the manifold pressure/torque gauges 
and engine rpm. Under this proposal, the value of K3 would 
be determined from approved data from the test airplane. In the absence 
of flight test data and at the discretion of the Administrator a value 
of K3 = 17 could still be used as under the current rule.
    The only difference between the current formula and the proposed 
formula is the power correction constant. The current regulation 
requires the use of 17 for this constant. The K3=17 value is 
an average value that was derived from FAA tests on seven aircraft 
where the variation was from 1.5 to 39.3. Although the use of an 
average value simplifies the test plan, it could penalize an applicant 
who can prove lower values of K3 by test data. Therefore, 
the FAA proposes a formula that allows the applicant to use a lower 
value for K3 when it has test data to support that value, or 
to continue to use a value of 17 with the Administrator's approval when 
test data is not available. The proposed formula is also consistent 
with the JAR.

Section G36.301  Aircraft Noise Limits

    Current section G36.301(b) states that the noise level must not 
exceed 73 dB(A) up to and including aircraft weights of 1,320 pounds 
(600 kg.), and that for weights greater than 1,320 pounds the noise 
limit increases at the rate of 1 dB/165 pounds up to 85 dB(A) at 3,300 
pounds, after which it is constant at 85 dB(A) up to and including 
19,000 pounds.
    As previously discussed, considerations of microphone location, 
configuration, and resulting noise limits are interrelated. Since the 
proposed changes to the noise measurement procedures of section 
G36.107(a) would result in increases in the measured noise levels of 
about 3 dB(A), the FAA proposes to increase the limits in section 
36.301(b) from 73 dB(A) to 76 dB(A) and from 85 dB(A) to 88 dB(A). This 
change would account for the revised microphone height and 
configuration requirements. The increased limit is not expected to 
result in any increase or decrease in the noise stringency requirements 
of the current rule.
    In addition to the dB(A) changes discussed, the FAA is proposing a 
change to the interpolation requirement of section G36.301(b). For 
weights greater than 1,320 pounds, the allowable dB(A) would increase 
``with the logarithm of airplane weight at the rate of 9.83 dB(A) per 
doubling of weight until the limit of 88 dB(A) is reached * * *,'' 
rather than at the rate of 1 dB/165 pounds up to 85 dB(A) at 3,300 
pounds, as under the current rule. This change would harmonize 
interpolation under the FAA regulation with the comparable JAA 
regulation without change in noise stringency of the present Appendix 
G.

Paperwork Reduction Act

    There are no requirements for information collection associated 
with this proposed rule that would require approval under the Paperwork 
Reduction Act of 1995 (44 U.S.C. 3501 et seq.)

International Compatibility

    In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA's policy to comply with ICAO 
Standards and Recommended Practices to the maximum extent practicable. 
For this NPRM, the FAA has reviewed part 36 Appendix G and ICAO Annex 
16 Volume I, Chapter 10. The review showed that the following two items 
were left unharmonized: (1) For fixed pitch type propellers, part 36 
section G36.201 specifies a simplified data correction procedure if the 
engine test power is within 5% of the reference power. The Annex 16 
does not have a corresponding simplification and, (2) The part 36 
section G36.111 allows the use of maximum continuous installed power 
during the second segment of the flight path. The power definition in 
Annex 16 for the second segment is defined as maximum power in Chapter 
10 section 10.5.2. The maximum installed power is typically lower than 
the maximum power and applicable only to older engines. The above two 
unharmonized items only effect a small percentage of the airplanes in 
the fleet and therefore are not significant enough to be considered as 
harmonization issues.

Regulatory Evaluation Summary

    Four principal requirements pertain to the economic impacts of 
changes to the Federal Regulations. First, Executive Order 12866 
directs Federal agencies to promulgate new regulations or modify 
existing regulations after consideration of the expected benefits to 
society and the expected costs. Second, the Regulatory Flexibility Act 
of 1980 requires agencies to analyze the economic impact of regulatory 
changes on small entities. Third, the Office of Management and Budget 
directs agencies to assess the effect of regulatory changes on 
international trade. Finally, Public Law 104-4 requires federal 
agencies to assess the impact of any federal mandates on state, local, 
tribal government, and the private sector. In conducting these 
analyses, the FAA has determined that this rule: (1) would generate 
cost savings that would exceed any costs; (2) is not ``significant'' as 
defined under section 3(f) of Executive Order 12866 and Department of 
Transportation's (DOT) policies and procedures (44 FR 11034, February 
26, 1979); (3) would not have a significant impact on a substantial 
number of small entities; and (4) would not impose restraints on 
international trade. Finally, the FAA has determined that the proposal 
would not impose a federal mandate on state, local, or tribal 
governments, or the private sector of $100 million per year. These 
analyses, available in the docket, are summarized below.
    The benefit of the proposed rule is that it would harmonize the 
U.S. noise certification regulations with the European Joint Aviation 
Requirements for propeller-driven small airplanes. The proposed changes 
would provide nearly uniform noise certification standards for 
airplanes certificated in the United States and by the European Joint 
Aviation Authorities (JAA). This is expected to reduce the number of 
noise tests that need to be conducted. The costs to implement the 
proposal are negligible, if any. There are no additional costs imposed 
by this proposal.

Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to ensure that small entities are not unnecessarily and 
disproportionately burdened by government regulations. The RFA requires 
a Regulatory Flexibility Analysis if a rule would have a significant 
economic impact on a

[[Page 64149]]

substantial number of small entities. Because the costs imposed by this 
rule would be negligible, the Agency concludes that the proposed rule 
would not have a significant economic impact on a substantial number of 
small entities.

International Trade Impact Statement

    The FAA has determined that the proposed rule would promote the 
sale of foreign products and services in the United States and the sale 
of U.S. products and services in foreign countries. This determination 
is based on the FAA's determination that the rule would align U.S. 
standards and JAA member standards for noise certification for 
propeller-driven small airplanes.

Environmental Analysis

    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. In accordance with FAA Order 1050.1D, paragraph 32, the 
FAA proposes that there are no extraordinary circumstances warranting 
preparation of an environmental assessment for this proposed rule.

Federalism Implications

    The proposed regulations would not have substantial direct effects 
on the states, on the relationship between national government and the 
states, or on the distribution of power and responsibilities among 
various levels of government. Thus, in accordance with Executive Order 
12612, it is determined that such a regulation would not have 
federalism implications warranting the preparation of a Federalism 
Assessment.

Unfunded Mandates

    Title II of the Unfunded Mandates Reform Act of 1995 (the Act), 
enacted as Pub. L. 104-4 on March 22, 1995, requires each Federal 
agency, to the extent permitted by law, to prepare a written assessment 
of the effects of any Federal mandate in a proposed or final agency 
rule that may result in the expenditure by State, local, and tribal 
governments, in the aggregate, or by the private sector, of $100 
million or more (adjusted annually for inflation) in any one year. 
Section 204(a) of the Act, 2 U.S.C. 1534(a), requires the Federal 
agency to develop an effective process to permit timely input by 
elected officers (or their designees) of State, local, and tribal 
governments on a proposed ``significant intergovernmental mandate.'' A 
``significant intergovernmental mandate'' under the Act is any 
provision in a Federal agency regulation that would impose an 
enforceable duty upon State, local, and tribal governments, in the 
aggregate, of $100 million (adjusted annually for inflation) in any one 
year. Section 203 of the Act, 2 U.S.C. 1533, which supplements section 
204(a), provides that before establishing any regulatory requirements 
that might significantly or uniquely affect small governments, the 
agency shall have developed a plan that, among other things, provides 
for notice to potentially affected small governments, if any, and for a 
meaningful and timely opportunity to provide input in the development 
of regulatory proposals.
    This rule does not contain a Federal intergovernmental or private 
sector mandate that exceeds $100 million a year, therefore the 
requirements of the Act do not apply.

List of Subjects in 14 CFR Part 36

    Agriculture, Aircraft, Noise control.

The Proposed Amendments

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

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.

    2. Appendix G of part 36 is amended by revising sections 
G36.107(a), G36.201(b), including Figure G1, G36.201(c), G36.201(d)(1), 
G36.201(d)(4), and G36.301(b), including Figure G2, to read as follows:

Appendix G to Part 36--Takeoff Noise Requirements for Propeller-
Driven Small Airplane and Propeller-Driven Commuter Category 
Airplane Certification Tests on or After December 22, 1988

* * * * *

Sec. G36.107  Noise Measurement Procedures.

    (a) The microphone must be a pressure type, 12.7 mm in diameter, 
with a protective grid, mounted in an inverted position such that 
the microphone diaphragm is 0.7 mm above and parallel to a white-
painted metal circular plate. This white-painted metal plate shall 
be 40 cm in diameter and at least 2.5 mm thick. The plate shall be 
placed horizontally and flush with the surrounding ground surface 
with no cavities below the plate. The microphone must be located 
three-quarters of the distance from the center to the back edge of 
the plate along a radius normal to the line of flight of the test 
airplane.
* * * * *

Sec. G36.201  Corrections to Test Results.

* * * * *
    (b) Atmospheric absorption correction is required for noise data 
obtained when the test conditions are outside those specified in 
Figure G1. Noise data outside the applicable range must be corrected 
to 59 F and 70 percent relative humidity by an FAA approved method.

[[Page 64150]]

[GRAPHIC] [TIFF OMITTED] TP18NO98.000



BILLING CODE 4910-13-C

    (c) Helical tip Mach number and power corrections must be made 
as follows:
    (1) Corrections for helical tip Mach number and power 
corrections must be made if--
    (i) The propeller is a variable pitch type; or
    (ii) The propeller is a fixed pitch type and the test power is 
not within 5 percent of the reference power.
    (2) No corrections for helical tip Mach number variation need to 
be made if the propeller helical tip Mach number is:
    (i) At or below 0.70 and the test helical tip Mach number is 
within 0.014 of the reference helical tip Mach number.
    (ii) Above 0.70 and at or below 0.80 and the test helical tip 
Mach number is within 0.007 of the reference helical tip Mach 
number.
    (iii) Above 0.80 and the test helical tip Mach number is within 
0.005 of the reference helical tip Mach number. For mechanical 
tachometers, if the helical tip Mach number is above 0.8 and the 
test helical tip Mach number is within 0.008 of the reference 
helical tip Mach number.
    (d) * * *
    (1) Measured sound levels must be corrected from test day 
meteorological conditions to reference conditions by adding an 
increment equal to--

Delta (M) = (H  - 0.7 HR)/1000

where H is the height in feet under test conditions, 
HR is the height in feet under reference conditions when 
the aircraft is directly over the noise measurement point and 
 is the rate of absorption for the test day conditions at 
500 Hz as specified in SAE ARP 866A, entitled ``Standard Values of 
Atmospheric Absorption as a function of Temperature and Humidity for 
use in Evaluating Aircraft Flyover Noise'' as incorporated by 
reference under Sec. 36.6.
* * * * *
    (4) Measured sound levels in decibels must be corrected for 
engine power by algebraically adding an increment equal to--

Delta(3) = K3 log (PR/P)

where PR and P are the test and reference engine 
powers respectively obtained from the manifold pressure/torque 
gauges and engine rpm. The value of K3 shall be 
determined from approved data from the test airplane. In the absence 
of flight test data and at the discretion of the Administrator, a 
value of K3 = 17 may be used.
* * * * *

Sec. G36.301  Aircraft Noise Limits.

* * * * *
    (b) The noise level must not exceed 76 dB (A) up to and 
including aircraft weights of 1,320 pounds (600 kg). For aircraft 
weights greater than 1,320 pounds, the limit increases from that 
point with the logarithm of airplane weight at the rate of 9.83 dB 
(A) per doubling of weight, until the limit of 88 dB (A) is reached, 
after which the limit is constant up to and including 19,000 pounds 
(8,618 kg). Figure G2 shows noise level limits vs airplane weight.

BILLING CODE 4910-13-P


[[Page 64151]]

[GRAPHIC] [TIFF OMITTED] TP18NO98.001



BILLING CODE 4910-13-C

    Issued in Washington, DC, on November 9, 1998.
James D. Erickson,
Director of Office of Environment and Energy.
[FR Doc. 98-30578 Filed 11-17-98; 8:45 am]
BILLING CODE 4910-13-P