801

Federal Aviation Administration, DOT

Pt. 36, App. A

(1) The term 0.01[

a

(i)

¥

a

(i)

0

]QK is the ad-

justment for the effect of the change in

sound attenuation coefficient, and

a

(i) and

a

(i)

0

are the coefficients for the test and ref-

erence atmospheric conditions respectively,

determined under section A36.7 of this appen-

dix;

(2) The term 0.01

a

(i)

0

(QK

¥

Q

r

K

r

) is the ad-

justment for the effect of the change in the

noise path length on the sound attenuation;

(3) The term 20 log(QK/Q

r

K

r

) is the adjust-

ment for the effect of the change in the noise

path length due to the inverse square law;

(4) QK and Q

r

K

r

are measured in meters and

a

(i) and

a

(i)

0

are expressed in dB/100 m.

A36.9.3.2.1.1

*PNLT Correction. *

(a) Convert the corrected values, SPL(i)

r

,

to PNLT

r

;

(b) Calculate the correction term

D

1

using

the following equation:

D

1

= PNLT

r

¥

PNLTM

A36.9.3.2.1.2 Add

D

1

arithmetically to the

EPNL calculated from the measured data.

A36.9.3.2.2 If, during a test flight, several

peak values of PNLT that are within 2 dB of

PNLTM are observed, the procedure defined

in section A36.9.3.2.1 must be applied at each

peak, and the adjustment term, calculated

according to section A36.9.3.2.1, must be

added to each peak to give corresponding ad-

justed peak values of PNLT. If these peak

values exceed the value at the moment of

PNLTM, the maximum value of such exceed-

ance must be added as a further adjustment

to the EPNL calculated from the measured

data.

A36.9.3.3

*Adjustments to duration correction. *

A36.9.3.3.1 Whenever the measured flight

paths and/or the ground velocities of the test

conditions differ from the reference flight

paths and/or the ground velocities of the ref-

erence conditions, duration adjustments

must be applied to the EPNL values cal-

culated from the measured data. The adjust-

ments must be calculated as described below.

A36.9.3.3.2 For the flight path shown in Fig-

ure A36–6, the adjustment term is calculated

as follows:

D

2

=

¥

7.5 log(QK/Q

r

K

r

) + 10 log(V/V

r

)

(a) Add

D

2

arithmetically to the EPNL cal-

culated from the measured data.

A36.9.3.4

*Source noise adjustments. *

A36.9.3.4.1 To account for differences be-

tween the parameters affecting engine noise

as measured in the certification flight tests,

and those calculated or specified in the ref-

erence conditions, the source noise adjust-

ment must be calculated and applied. The

adjustment is determined from the manufac-

turer’s data approved by the FAA. Typical

data used for this adjustment are illustrated

in Figure A36–8 that shows a curve of EPNL

versus the engine control parameter

µ

, with

the EPNL data being corrected to all the

other relevant reference conditions (airplane

mass, speed and altitude, air temperature)

and for the difference in noise between the

test engine and the average engine (as de-

fined in section B36.7(b)(7)). A sufficient

number of data points over a range of values

of

µ

r

is required to calculate the source noise

adjustments for lateral, flyover and ap-

proach noise measurements.

A36.9.3.4.2 Calculate adjustment term

D

3

by

subtracting the EPNL value corresponding

to the parameter

µ

from the EPNL value cor-

responding to the parameter

µ

r

. Add

D

3

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