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need be made if the propeller helical tip Mach number
is:
1) at or below 0.70 and the test helical tip Mach number
is within 0.014 of the reference helical tip
Mach number;
2) above 0.70 and at or below 0.80 and the test helical
tip Mach number is within 0.007 of the reference
helical tip Mach number;
3) above 0.80 and the test helical tip Mach number is
within 0.005 of the reference helical tip Mach
number. For mechanical tachometers, if the helical
tip Mach number is above 0.8 and the test helical tip
Mach number is within 0.008 of the reference helical
tip Mach number.
Outside these limits measured noise levels shall be
adjusted for helical tip Mach number by an increment
equal to:
d) Measured sound levels shall be adjusted for engine
power by algebraically adding an increment equal to:
where PT and P, are the test and reference engine
powers respectively obtained from the manifold
pressure/torque gauges and engine rpm. The value of K3
shall be determined from approved data from the test
aeroplane. In the absence of flight test data and at the
discretion of the certificating authority a value of
Kg = 17 may be used. The reference power PR shall be
that obtained at the reference height pressure and
temperature assuming an ISA temperature lapse rate
with height.
6. REPORTING OF DATA TO THE
CERTIFICATING AUTHORITY
AND VALIDITY OF RESULTS
6.1 Data reporting
which shall be added algebraically to the measured noise 6.1.1 Measured and corrected sound pressure levels
level, where MT and MR are the test and reference
obtained with equipment conforming to the specifications Mach numbers The value of K2 described in Section 4 of this appendix shall be reported.
shall be determined from approved data from the test
aeroplane. In the absence of-flight test data and at the 6.1.2 The type of equipment used for measurement and
discretion of the certificating a of K2 = analysis of all acoustic aeroplane perfomance and meteorog1r5e0a
tmera yth baen uosre edq fuoarl MtoT M leRss n toh acno rMreRct;i ohno wise vaeprp, lfieodr .M T logical data shall be reported.
6.1.3 The following atmospheric environmental data,
Note.- The reference helical tip Mach number MK is measured immediately before, after, or during each test at the
the one corresponding to the reference conditions above observation points prescribed in Section of this appendix
the measurement point:
shall be reported:
where
a) air temperature and relative humidity;
b) wind speeds and wind directions; and
c) atmospheric pressure.
where D is the propeller diameter in metres. 6.1.4 Comments on local topography, ground cover and
events that might interfere with sound recordings shall be
VT is the true airspeed of the aeroplane in rejizrence repofled.
conditions in metres per second.
6.1.5 The following aeroplane information shall be
N is the propeller speed in reference conditions in rpm.
If N is not available, its value can be taken as the
average of the propeller speeds over nominally identical a) type, model and serial numbers of aeroplane, engine(s)
power conditions during the flight tests. and propeller(s);
c is the reference day speed of sound at the altitude of the b) any modifications or non-standard equipment likely to
aeroplane in metres per second based on the temperature affect the noise characteristics of the aeroplane;
at the reference height assuming an ZSA temperature
lapse rate with height. c) maximum certificated take-off mass;
APP 6-5 24/11/05
Annex 16 - Environmental Protection Volume I
d) for each overflight, airspeed and air temperature at
the flyover altitude determined by properly calibrated
instruments;
e) for each overflight, engine performance as manifold
pressure or power, propeller speed in revolutions per
minute and other relevant parameters determined by
properly calibrated instruments;
f ) aeroplane height above the measurement point; and
g) corresponding manufacturer's data for the reference
conditions relevant to 6.1.5 d), e) and f).
6.2 Validity of results
6.2.1 The measuring point shall be overflown at least six
times. The test results shall produce an average noise level
(L,) value and its 90 per cent confidence limits, the noise
level being the arithmetic average of the corrected acoustical
measurements for all valid test runs over the measuring point.
6.2.2 The samples shall be large enough to establish
statistically a 90 per cent confidence limit not exceeding
*1.5 &(A). No test results shall be omitted &om the averaging
process, unless otherwise specified by the certificating
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