Code of Federal Regulations - Title 14

978

14 CFR Ch. I (1–1–14 Edition)

Pt. 36, App. J

spherical spreading and duration from the
off-reference altitude.

tween reference airspeed and adjusted ref-
erence airspeed is calculated from:

<delta>J

=10 log

) dB;

Where <delta>J

is the quantity in decibels

that must be algebraically added to the
measured SEL noise level to correct for the
influence of the adjustment of the reference
airspeed on the duration of the measured fly-
over event as perceived at the noise measure-
ment station, V

is the reference airspeed as

prescribed under section J36.3.(c) of this ap-
pendix, and V

is the adjusted reference air-

speed as prescribed under section J36.105(c)
of this appendix.

(d) No correction for source noise during

the flyover other than the variation of
source noise accounted for by the adjust-
ment of the reference airspeed prescribed for
under section J36.105(c) of this appendix need
be applied.

(e) No correction for the difference be-

tween the reference ground speed and the ac-
tual ground speed need be applied.

(f) No correction for off-reference atmos-

pheric attenuation need be applied.

(g) The SEL adjustments must be less than

2.0 dB(A) for differences between test and ref-
erence flight procedures prescribed under
section J36.105 of this appendix unless a larg-
er adjustment value is approved by the FAA.

(h) All data used and calculations per-

formed under this section must be docu-
mented and provided under the reporting re-
quirements specified under section J36.111 of
this appendix.

ART

D—N

OISE

IMITS

ROCEDURE

NDER

§ 36.805

Section J36.301 Noise Measurement, Evaluation,

and Calculation.

Compliance with this part of this appendix

must be shown with noise levels measured,
evaluated, and calculated as prescribed
under parts B and C of this appendix.

Section J36.303 [Reserved]

Section J36.305 Noise Limits.

For compliance with this appendix, the

calculated noise levels of the helicopter, at
the measuring point described in section
J36.101 of this appendix, must be shown to
not exceed the following (with appropriate
interpolation between weights):

(a) For primary, normal, transport, and re-

stricted category helicopters having a max-
imum certificated takeoff weight of not
more than 7,000 pounds that are noise tested
under this appendix, the Stage 2 noise limit
is 82 decibels SEL for helicopters up to 1,737
pounds maximum certificated takeoff weight
at which the noise certification is requested,

and increasing at a rate of 3.0 decibels per
doubling of weight thereafter. The limit may
be calculated by the equation: L

(limit) =

82 + 3.0 [log

(MTOW/1737)/log

(2)] dB, where

MTOW is the maximum takeoff weight, in
pounds, for which certification under this ap-
pendix is requested.

(b) The procedures required in this amend-

ment shall be done in accordance with the
International Electrotechnical Commission
IEC Publication No. 804, entitled ‘‘Inte-
grating-averaging Sound Level Meters,’’
First Edition, dated 1985. This incorporation
by reference was approved by the Director of
the Federal Register in accordance with 5
U.S.C. 552(a) and 1 CFR part 51. Copies may
be obtained from the Bureau Central de la
Commission Electrotechnique Inter-
nationale, 1, rue de Varembe, Geneva, Swit-
zerland or the American National Standard
Institute, 1430 Broadway, New York City,
New York 10018, or at the National Archives
and Records Administration (NARA). For in-
formation on the availability of this mate-
rial at NARA, call 202–741–6030, or go to:
http://www.archives.gov/federal

lregister/

code

loflfederallregulations/

ibr

llocations.html.

[Doc. No. 26910, 57 FR 42855, Sept. 16, 1992, as
amended by Amdt. 36–20, 57 FR 46243, Oct. 7,
1992; 69 FR 18803, Apr. 9, 2004; Amdt. 36–25, 69
FR 31234, June 2, 2004]

PPENDIX

ART

36—N

OISE

QUIREMENTS FOR

ILTROTORS

NDER

UBPART

General

Noise Evaluation Measure

Noise Measurement Reference Points

Noise Limits

Trade-offs

Noise Certification Reference Procedures

Test Procedures

Section K1 General

This appendix prescribes noise limits and

procedures for measuring noise and adjusting
the data to standard conditions for tiltrotors
as specified in § 36.1 of this part.

Section K2 Noise Evaluation Measure

The noise evaluation measure is the effec-

tive perceived noise level in EPNdB, to be
calculated in accordance with section A36.4
of Appendix A to this part, except correc-
tions for spectral irregularities must be de-
termined using the 50 Hz sound pressure
level found in section H36.201 of Appendix H
to this part.

Section K3 Noise Measurement Reference Points

The following noise reference points must

be used when demonstrating tiltrotor com-
pliance with section K6 (Noise Certification

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