An aeroplane, when tested in accordance with the flight test procedures of
2.6, shall not exceed the noise levels specified in 2.4 at the following
points:
a) Lateral Noise Measurement Point: The point on a line parallel to and 650 m from the runway centre line, or
extended runway centre line, where the noise level is a maximum during
take-off;
b) Flyover Noise Measurement Point: The point on the extended centre line of the runway and at a distance of
6.5 km from the start of roll; and
c) Approach Noise Measurement Point: The point on the ground, on the extended centre line of the runway, 120 m
(394 ft) vertically below the 3° descent path originating from a point 300 m
beyond the threshold. On level ground this corresponds to a position 2000 m from the threshold.
NOISE MEASUREMENT PROCEDURES
The applicant should submit to the certificating authority for their
review and approval technical procedures for the measurement of aircraft noise
certification levels. The technical procedures described in the following
sections of this chapter should be considered as generally appropriate for all
aircraft types. For procedures specific to Appendices 2, 4 and 6 see
respectively Chapters 4, 5 and
Test
site selection
For aeroplanes, when the flight path intercept equivalent test
procedure is used, and for helicopters, it may not be necessary for the test
site to be located at an airport. Details of the proposed noise certification
test-site locations should be submitted to the certificating authority for
review and approval. Some test-site criteria that could support selection of a
non-airport test site include level terrain, reduced air traffic, reduced
ambient noise, improved weather conditions (temperature, humidity and wind),
improved microphone placement, availability of field surveys, improved locations
for aircraft position monitoring and improved pilot sight and handling.
*Terrain:
Uneven terrain having features such as mounds or furrows can result
in reflections that could influence the measured sound levels. Vegetation can
reduce the amount of sound that is reflected from the ground surface. In most
cases this effect results in a reduced sound level, but under some
circumstances the level may be higher. Testing over a smooth hard surface, such
as a paved area, will generally result in a higher sound level.
*Grass:
For noise measurement points under the flight path 7.5 m (25 ft)
radius circles of mowed grass (not exceeding 8 cm (3 in) height) are
acceptable. For noise measurement points located to the side of the flight
path, the grass may be mowed in a semicircle of 7.5 m (25 ft) radius facing the
line of flight.
*Snow:
Snow in the area surrounding the noise measurement points may
provide excessive absorption of aircraft sound reflected from the ground. Noise
measurement points have been approved when snow within a 15 m (50 ft) radius of
the noise measurement points has been removed. However, snow should not be
piled at the borders facing the line of flight.
*Ploughed fields:
Earthen or sandy surfaces within a 7.5 m (25 ft) radius of the noise
measurement points shall be reasonably tamped down. Ploughed furrows, silt or
soft, powdered surfaces are unacceptable.
*Obstructions:
Obstructions in the vicinity of the noise measurement points such as
buildings, walls, trees, vehicles and test personnel, if close enough, may be
unacceptable because of reflections that influence measured noise levels. There
should be no obstructions that significantly influence the sound field from the
aircraft within a conical space above a point on the ground vertically below
the microphone at each noise measurement point. The cone is defined by an axis
normal to the ground and by a half angle of 80º (75º for light propeller-driven
aeroplanes) from the axis as illustrated in Figure 3-1.
*Anomalous meteorological conditions:
Certain geographical areas are more susceptible to anomalous
meteorological conditions than others (i.e. large variations, or inversions, of
temperature or humidity, excessive turbulence or thermally induced vertical
winds). The applicant may conduct certification testing only as approved by the
certificating authority.
Maximum noise levels
The maximum noise levels of those aeroplanes covered, when determined in
accordance with the noise evaluation method of Appendix 1, shall not exceed the
following:
a) at lateral and
approach noise measurement points: 108 EPNdB for aeroplanes with maximum certificated
take-off mass of 272
000 kg or over, decreasing linearly with the logarithm of the mass at the rate
of 2 EPNdB per halving of the mass
down to 102 EPNdB at 34 000 kg, after which the limit remains constant;
b) at flyover noise
measurement point: 108 EPNdB for aeroplanes with maximum certificated take-off mass of 272 000
kg or over, decreasing linearly with the logarithm of the mass at the rate of 5
EPNdB per halving of the mass down to 93 EPNdB at 34 000 kg, after which the
limit remains constant.
The maximum noise levels of those aeroplanes covered, when determined in
accordance with the noise evaluation method of Appendix 1, shall not exceed the
following:
*At lateral noise measurement point
106 EPNdB
for aeroplanes with maximum certificated take-off mass of 400 000 kg or over,
decreasing linearly with the logarithm of the mass down to 97 EPNdB at 35 000
kg, after which the limit remains constant.
*At flyover noise measurement point
a) Aeroplanes with
two engines or less:
104 EPNdB
for aeroplanes with maximum certificated take-off mass of 325 000 kg or over,
decreasing linearly with
the
logarithm of the mass at the rate of 4 EPNdB per halving of mass down to 93
EPNdB, after which the limit remains
constant.
b) Aeroplanes with
three engines:
As a) but with 107 EPNdB for aeroplanes
with maximum certificated take-off mass of 325 000 kg or over as defined b),
whichever is the lower.
c) Aeroplanes with
four engines or more:
As a) but
with 108 EPNdB for aeroplanes with maximum certificated take-off mass of 325
000 kg or over or as defined by b), whichever is the lower.
*At approach noise measurement point
108
EPNdB for aeroplanes with maximum certificated take-off mass of 280 000 kg or
over, decreasing linearly with the logarithm of the mass down to 101 EPNdB at
35 000 kg, after which the limit remains constant.
EQUATIONS FOR THE CALCULATION OF NOISE LEVELS AS A FUNCTION OF TAKE-OFF MASS
Trade-offs
If the
maximum noise levels are exceeded at one or two measurement points:
a) the sum of excesses shall not be greater than 4 EPNdB, except that in
respect of four-engined aeroplanes powered by engines with a bypass ratio of 2
or more and for which the application for a certificate of airworthiness for the
prototype was accepted, or another equivalent prescribed procedure was carried
out by the certificating authority, before 1 December 1969, the sum of any
excesses shall not be greater than 5 EPNdB;
b) any excess at any single point shall not be greater than 3 EPNdB; and
c) any excesses shall be offset by corresponding reductions at the other
point or points.
Test procedures
Take-off
test procedure
Average take-off thrust2 shall be used from the start of take-off to the
point at which a height of at least 210 m (690 ft) above the runway is reached,
and the thrust thereafter shall not be reduced below that thrust which will
maintain a climb gradient of at least 4 per cent.
A speed of at least V2 + 19 km/h (V2 + 10 kt) shall be attained as soon as
practicable after lift-off and be maintained throughout the take-off noise certification
test.
A constant take-off configuration selected by the applicant shall be
maintained throughout the take-off noise certification demonstration test except
that the landing gear may be retracted.
Approach
test procedure
The aeroplane shall be stabilized and following a 3° ± 0.5° glide path.
The approach shall be made at a stabilized airspeed of not less than 1.3 VS
+ 19 km/h (1.3 VS + 10 kt) with thrust stabilized during approach and over the
measuring point and continued to a normal touchdown.
The
configuration of the aeroplane shall be with maximum allowable landing flap
setting.
