816 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 36, App. G 

made using the nominal value of k when 
M

T

is larger than M

R

. The reference hel-

ical tip Mach number M

R

is the Mach 

number corresponding to the reference 
conditions (RPM, airspeed, temperature) 
above the measurement point. 

(4) Measured sound levels in decibels must 

be corrected for engine power by algebra-
ically adding an increment equal to 

Delta (3) = K

3

log (P

R

/P

T

) 

where P

R

and P

T

are the test and reference 

engine powers respectively obtained from 
the manifold pressure/torque gauges and 
engine rpm. The value of K

3

shall be de-

termined from approved data from the 
test airplane. In the absence of flight 
test data and at the discretion of the Ad-
ministrator, a value of K

3

= 17 may be 

used. 

Sec. G36.203 Validity of Results. 

(a) The measuring point must be overflown 

at least six times. The test results must 
produce an average noise level (L

Amax

) value 

within a 90 percent confidence limit. The av-
erage noise level is the arithmetic average of 
the corrected acoustical measurements for 
all valid test runs over the measuring point. 

(b) The samples must be large enough to 

establish statistically a 90 percent con-
fidence limit not exceeding 

±

1.5 dB(A). No 

test results may be omitted from the aver-
aging process unless omission is approved by 
the FAA. 

PART D

—

NOISE LIMITS

 

Sec. G36.301 Aircraft noise limits. 

(a) Compliance with this section must be 

shown with noise data measured and cor-
rected as prescribed in Parts B and C of this 
appendix. 

(b) For single-engine airplanes for which 

the original type certification application is 
received before February 3, 2006 and multi- 
engine airplanes, the noise level must not ex-
ceed 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. 

(c) For single-engine airplanes for which 

the original type certification application is 
received on or after February 3, 2006, the 
noise level must not exceed 70dB(A) for air-
craft having a maximum certificated takeoff 
weight of 1,257 pounds (570 kg) or less. For 
aircraft weights greater than 1,257 pounds, 
the noise limit increases from that point 
with the logarithm of airplane weight at the 
rate of 10.75dB(A) per doubling of weight, 
until the limit of 85dB(A) is reached, after 
which the limit is constant up to and includ-
ing 19,000 pounds (8,618 kg). Figure G2 depicts 
noise level limits for airplane weights for 
single-engine airplanes. 

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