805 

Federal Aviation Administration, DOT 

Pt. 36, App. A 

being on a particular lateral line. The posi-
tion of K

r

and Q

r1

are determined from the 

following requirements. 

(i) Q

1

K and Q

r1

K

r

form the same angle 

q

1

 

with their respective flight paths; and 

(ii) The differences between the angles 

1

 

and 

r1

must be minimized using a method, ap-

proved by the FAA. The differences between 
the angles are minimized since, for geometri-
cal reasons, it is generally not possible to 
choose K

r

so that the condition described in 

paragraph A36.9.4.2(b)(2)(i) is met while at 
the same time keeping 

1

and 

r1

equal. 

N

OTE

: For the lateral noise measurement, 

sound propagation is affected not only by 
‘‘inverse square’’ and atmospheric attenu-
ation, but also by ground absorption and re-
flection effects which depend mainly on the 
angle. 

A36.9.4.2.1 In paragraphs A36.9.4.2(a)(2) and 

(b)(2) the time t

r1

is later (for Q

r1

K

r

>Q

1

K) 

than t

1

by two separate amounts: 

(1) The time taken for the airplane to trav-

el the distance Q

r1

Q

r0

at a speed V

r

less the 

time taken for it to travel Q

1

Q

0

at V; 

(2) The time taken for sound to travel the 

distance Q

r1

K

r

–Q

1

K. 

N

OTE

: For the flight paths described in 

paragraphs A36.9.4.2(a) and (b), the use of 
thrust or power cut-back will result in test 
and reference flight paths at full thrust or 
power and at cut-back thrust or power. 
Where the transient region between these 
thrust or power levels affects the final re-
sult, an interpolation must be made between 
them by an approved method such as that 
given in the current advisory circular for 
this part. 

A36.9.4.2.2 The measured values of SPL(i)

1

 

must be adjusted to the reference values 
SPL(i)

r1

to account for the differences be-

tween measured and reference noise path 
lengths and between measured and reference 
atmospheric conditions, using the methods 
of section A36.9.3.2.1 of this appendix. A cor-
responding value of PNL

r1

must be computed 

according to the method in section A36.4.2. 
Values of PNL

r

must be computed for times 

t

0

through t

n

. 

A36.9.4.2.3 For each value of PNL

r1

, a tone 

correction factor C

1

must be determined by 

analyzing the reference values SPL(i)

r

using 

the methods of section A36.4.3 of this appen-
dix, and added to PNL

r1

to yield PNLT

r1

. 

Using the process described in this para-
graph, values of PNLT

r

must be computed for 

times t

0

through t

n

. 

A36.9.4.3 

Duration correction. 

A36.9.4.3.1 The values of PNLT

r

cor-

responding to those of PNLT at each one- 
half second interval must be plotted against 
time (PNLT

r1

at time t

r1

). The duration cor-

rection must then be determined using the 
method of section A36.4.5.1 of this appendix, 
to yield EPNL

r

. 

A36.9.4.4 

Source Noise Adjustment. 

A36.9.4.4.1 A source noise adjustment, 

D

3

, 

must be determined using the methods of 
section A36.9.3.4 of this appendix. 

A36.9.5 F

LIGHT

P

ATH

I

DENTIFICATION

P

OSITIONS

 

Position Description 

A ...........

Start of Takeoff roll. 

B ...........

Lift-off. 

C ..........

Start of first constant climb. 

D ..........

Start of thrust reduction. 

E ...........

Start of second constant climb. 

F ...........

End of noise certification Takeoff flight path. 

G ..........

Start of noise certification Approach flight path. 

H ..........

Position on Approach path directly above noise 

measuring station. 

I ............

Start of level-off. 

J ...........

Touchdown. 

K ...........

Noise measurement point. 

K

r

..........

Reference measurement point. 

K

1

.........

Flyover noise measurement point. 

K

2

.........

Lateral noise measurement point. 

K

3

.........

Approach noise measurement point. 

M ..........

End of noise certification Takeoff flight track. 

O ..........

Threshold of Approach end of runway. 

P ...........

Start of noise certification Approach flight track. 

Q ..........

Position on measured Takeoff flight path cor-

responding to apparent PNLTM at station K See 
section A36.9.3.2. 

Q

r

.........

Position on corrected Takeoff flight path cor-

responding to PNLTM at station K. See section 
A36.9.3.2. 

V ...........

Airplane test speed. 

V

r

..........

Airplane reference speed. 

A36.9.6 F

LIGHT

P

ATH

D

ISTANCES

 

Distance Unit 

Meaning 

AB ........

Feet (meters)  Length of takeoff roll. The distance 

along the runway between the 
start of takeoff roll and lift off. 

AK ........

Feet 

(meters) Takeoff measurement distance. 

The distance from the start of 
roll to the takeoff noise measure-
ment station along the extended 
center line of the runway. 

AM .......

Feet (meters)  Takeoff flight track distance. The 

distance from the start of roll to 
the takeoff flight track position 
along the extended center line of 
the runway after which the posi-
tion of the airplane need no 
longer be recorded. 

QK .......

Feet (meters)  Measured noise path. The distance 

from the measured airplane po-
sition Q to station K. 

Q

r

K

r

.....

Feet 

(meters)  Reference noise path. The dis-

tance from the reference air-
plane position Q

r

to station K

r

. 

K

3

H ......

Feet 

(meters) Airplane approach height. The 

height of the airplane above the 
approach measuring station. 

OK

3

......

Feet (meters)  Approach measurement distance. 

The distance from the runway 
threshold to the approach meas-
urement station along the ex-
tended center line of the runway. 

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