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a line at right angles to and at the specified distance of the change in sound attenuation coefficient, and a(i)
Ji-om the overflight flight track RS. and a(i), are the coefficients for the test and reference
c) The distance RS is the distance over which the helicop- atmospheric conditions respectively, obtained from
ter position is measured and synchronized with the noise Section 7 of this appendix;
measurements (see 2.3.2 of this appendix). - the term 0.01 a(i), (QK - Q X ) accounts for the effect
of the change in the noise path length on the sound
attenuation;
8.2.3 Approach profile
- the term 20 log (QWQA) accounts for the effect of the
Note.- Figure A2-6 illustrates a typical approach profile. change in the noise path length due to the "inverse
square" law;
a) The helicopter is initially stabilized at the specified
approach path angle at point G and continues >hiugh - QK and Q,.K, are measured in metres and a(i) and a(i),
point H, point I and then to touchdown. are in dBilOO m.
b) Position K3 is the approach flight path reference
point and K3H is the height of the helicopter
overhead the appmach flight path reference point. Positions
K3' and K3" are associated noise measurement
locations on a line at right angles to and at the specified
distanceJLom the approach flight path track PU.
c) The distance PU is the distance over which the helicopter
position is measured and synchronized with the
noise measurements (see 2.3.2 ofthis appendix).
8.3 Adjustments of PNL and PNLT
Note.- The portions of the test flight path and reference
flight path which are significant for the EPNL calculation are
8.3.2 The corrected values SPL(i), shall be converted to
PNLT,, and a correction term calculated as follows:
A, = PNLT, - PNLTM
8.3.3 A, shall be added algebraically to the EPNL
calculated from the measured data.
8.3.4 If, during a test flight, several peak values of PNLT
are observed which are within 2 dB of PNLTM, the procedure
defined in 8.3.1, 8.3.2 and 8.3.3 shall be applied at each peak,
and the adjustment term so calculated shall be added to each
peak to give corresponding adjusted peak values of PNLT. If
these peak values exceed that at the moment of PNLTM, the
maximum value of such excess shall be added as a further
adjustment to the EPNL calculated from the measured data.
APP 2-21 2411 1105
Annex 16 - Environmental Protection Volume I
Measurements made over this range
Figure A2-4. mica1 test and reference profdes
DT
y- 7 E
I I
I I
I I
I I
I I
I I
I I
I I
I 0 I
RP
I
S
I
0
K2'/ I
I I
Measurements made over this range
Figure A2-5. Typical overflight profile
APP 2-22
Appendix 2 Annex 16 - Environmental Protection
Measurements made over this range
Figure A2-6. 'Qpical approach profile
Figure A2-7. Profile characteristics influencing sound level
APP 2-23
Annex 16 - Environmental Protection Volume I
8.4 Adjustments to
duration correction
8.4.1 Whenever the measured flight paths andor the
ground velocities in the test conditions differ from the refer-
8.6 Flight path identification
positions and parameters
8.6.1 General
ence flight paths andor the ground velocities in the reference Position/
conditions, duration adjustments shall be applied to the EPNL parameter Description
values calculated from the measured data. The adjustments
shall be calculated as described below. K Noise measurement point.
Kr Reference measurement point.
8.4.2 Referring to the flight path shown in Figure A2-7,
the adjustment term shall be calculated as follows: V Helicopter test ground speed.
A, = -7.5 log (QWQ,Kr) + 10 log OIN,) vr Helicopter reference ground speed.
which represents the adjustment to be added algebraically to
the EPNL calculated from the measured data.
8.5 Correction of noise
at source
VH Maximum speed in level flight at power not
exceeding maximum continuous power.
VNE Never exceed speed.
v~ Speed for best rate of climb.
8.6.2 Take-off (see Figure A2-4)
For overflight, if any combination of the following three
factors: Position Description
a) airspeed deviations from reference; A Start of noise certification take-off flight path.
b) rotor speed deviations from reference;
c) temperature deviations from reference;
results in an agreed noise correlating parameter whose value
deviates from the reference value of this parameter, then
source noise adjustments shall be determined from manufacturer's
data approved by the certificating authority. This
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