Pt. 36, App. J

14 CFR Ch. I (1-1-19 Edition)

monitoring station. Airspeed is stabilized at
0.9VH; 0.9VNE; 0.45VH + 65 kts (120 km/h); or
0.45VNE + 65 kts (120 km/h), whichever of the
four airspeeds is least, and maintained
throughout the measured portion of the flyover. Rotor speed is stabilized at the maximum normal operating RPM throughout the
10 dB-down time interval.
(1) For noise certification purposes, VH is
defined as the airspeed in level flight obtained using the minimum specification engine power corresponding to maximum continuous power available for sea level pressure of 2,116 psf (1,013.25 hPa) at 77 SectionF (25 SectionC)
ambient conditions at the relevant maximum certificated weight. The value of VH
and VNE used for noise certification must be
included in the Flight Manual.
(2) VNE 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]
PART B - NOISE MEASUREMENT PROCEDURE
UNDER Section 36.801

spaschal on DSK3GDR082PROD with CFR

Section J36.101 Noise certification test and
measurement conditions.
(a) General. This section prescribes the conditions under which helicopter noise certification 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 wooded areas.
(2) During the period when the flyover
noise measurement is within 10 dB of the
maximum A-weighted sound level, no obstruction that significantly influences the
sound field from the helicopter may exist
within a conical space above the noise measuring 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 degrees and 95 degrees Fahrenheit (2 degrees
and 35 degrees Celsius), inclusively, and relative humidity between 20 percent and 95
percent inclusively, except that testing may
not take place where combinations of temperature 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 kiloHertz.

(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 seconds;
(4) Measurements of ambient temperature,
relative humidity, wind speed, and wind direction must be made between 4 feet (1.2 meters) and 33 feet (10 meters) above the
ground. Unless otherwise approved by the
FAA, ambient temperature and relative humidity must be measured at the same height
above the ground.
(5) No anomalous wind conditions (including turbulence) or other anomalous meteorological conditions that will significantly affect 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 helicopter testing procedures and noise measurements must be conducted and processed
in a manner which yields the noise evaluation 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 conditions prescribed under section J36.3 of this
appendix, then with FAA approval, the reference test conditions used under this appendix may vary from the standard reference
test conditions, but only to the extent demanded 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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