832 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 36, App. J 

monitoring station. Airspeed is stabilized at 
0.9V

H

; 0.9V

NE

; 0.45V

H

+ 65 kts (120 km/h); or 

0.45V

NE

+ 65 kts (120 km/h), whichever of the 

four airspeeds is least, and maintained 
throughout the measured portion of the fly-
over. Rotor speed is stabilized at the max-
imum normal operating RPM throughout the 
10 dB-down time interval. 

(1) For noise certification purposes, V

H

is 

defined as the airspeed in level flight ob-
tained using the minimum specification en-
gine power corresponding to maximum con-
tinuous power available for sea level pres-
sure of 2,116 psf (1,013.25 hPa) at 77 

°

F (25 

°

C) 

ambient conditions at the relevant max-
imum certificated weight. The value of V

H

 

and V

NE

used for noise certification must be 

included in the Flight Manual. 

(2) V

NE

is the never-exceed airspeed. 

(d) The weight of the helicopter shall be 

the maximum takeoff weight at which noise 
certification is requested. 

Section J36.5 [Reserved] 

P

ART

B—N

OISE

M

EASUREMENT

P

ROCEDURE

 

U

NDER

§ 36.801 

Section J36.101 Noise certification test and 

measurement conditions. 

(a) 

General. 

This section prescribes the con-

ditions under which helicopter noise certifi-
cation tests must be conducted and the 
measurement procedures that must be used 
to measure helicopter noise during each test. 

(b) 

Test site requirements. 

(1) The noise 

measuring station must be surrounded by 
terrain having no excessive sound absorption 
characteristics, such as might be caused by 
thick, matted, or tall grass, shrubs, or wood-
ed areas. 

(2) During the period when the flyover 

noise measurement is within 10 dB of the 
maximum A-weighted sound level, no ob-
struction that significantly influences the 
sound field from the helicopter may exist 
within a conical space above the noise meas-
uring position (the point on the ground 
vertically below the microphone), the cone is 
defined by an axis normal to the ground and 
by half-angle 80 degrees from this axis. 

(c) 

Weather restrictions. 

The test must be 

conducted under the following atmospheric 
conditions: 

(1) No rain or other precipitation; 
(2) Ambient air temperature between 36 de-

grees and 95 degrees Fahrenheit (2 degrees 
and 35 degrees Celsius), inclusively, and rel-
ative humidity between 20 percent and 95 
percent inclusively, except that testing may 
not take place where combinations of tem-
perature and relative humidity result in a 
rate of atmospheric attenuation greater than 
10 dB per 100 meters (30.5 dB per 1000 ft) in 
the one-third octave band centered at 8 kilo-
Hertz. 

(3) Wind velocity that does not exceed 10 

knots (19 km/h) and a crosswind component 
that does not exceed 5 knots (9 km/h). The 
wind shall be determined using a continuous 
averaging process of no greater than 30 sec-
onds; 

(4) Measurements of ambient temperature, 

relative humidity, wind speed, and wind di-
rection must be made between 4 feet (1.2 me-
ters) and 33 feet (10 meters) above the 
ground. Unless otherwise approved by the 
FAA, ambient temperature and relative hu-
midity must be measured at the same height 
above the ground. 

(5) No anomalous wind conditions (includ-

ing turbulence) or other anomalous meteoro-
logical conditions that will significantly af-
fect the noise level of the helicopter when 
the noise is recorded at the noise measuring 
station; and 

(6) If the measurement site is within 6560 

feet (2,000 meters) of a fixed meteorological 
station (such as those found at airports or 
other facilities) the weather measurements 
reported for temperature, relative humidity 
and wind velocity may be used, if approved 
by the FAA. 

(d) 

Helicopter testing procedures. 

(1) The hel-

icopter testing procedures and noise meas-
urements must be conducted and processed 
in a manner which yields the noise evalua-
tion measure designated Sound Exposure 
Level (SEL) as defined in section J36.109(b) 
of this appendix. 

(2) The helicopter height relative to the 

noise measurement point sufficient to make 
corrections required under section J36.205 of 
this appendix must be determined by an 
FAA-approved method that is independent of 
normal flight instrumentation, such as radar 
tracking, theodolite triangulation, laser 
trajectography, or photographic scaling 
techniques. 

(3) If an applicant demonstrates that the 

design characteristics of the helicopter 
would prevent flight from being conducted in 
accordance with the reference test condi-
tions prescribed under section J36.3 of this 
appendix, then with FAA approval, the ref-
erence test conditions used under this appen-
dix may vary from the standard reference 
test conditions, but only to the extent de-
manded by those design characteristics 
which make compliance with the reference 
test conditions impossible. 

Section J36.103 [Reserved] 

Section J36.105 Flyover test conditions. 

(a) This section prescribes the flight test 

conditions and allowable random deviations 
for flyover noise tests conducted under this 
appendix. 

(b) A test series must consist of at least six 

flights. The number of level flights made 
with a headwind component must be equal to 

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