JAR 25.1401 Anti-collision light system
(a) General. The aeroplane must have an
anti-collision light system that –
(1) Consists of one or more approved
anti-collision lights located so that their light
will not impair the crew’s vision or detract
from the conspicuity of the position lights; and
(2) Meets the requirements of sub-paragraphs
(b) to (f) of this paragraph.
(b) Field of coverage. The system must
consist of enough light to illuminate the vital
areas around the aeroplane considering the
physical configuration and flight characteristics of
the aeroplane. The field of coverage must extend
in each direction within at least 75º above and 75º
below the horizontal plane of the aeroplane,
except that a solid angle or angles of obstructed
visibility totalling not more than 0·03 steradians is
allowable within a solid angle equal to 0·15
steradians centred about the longitudinal axis in
the rearward direction.
(c) Flashing characteristics. The arrange-ment
of the system, that is, the number of light
sources, beam width, speed of rotation, and other
characteristics, must give an effective flash
frequency of not less than 40, nor more than 100
cycles per minute. The effective flash frequency is
the frequency at which the aeroplane’s complete
anti-collision light system is observed from a
distance, and applies to each section of light
including any overlaps that exist when the system
consists of more than one light source. In
overlaps, flash frequencies may exceed 100, but
not 180 cycles per minute.
(d) Colour. Each anti-collision light must be
either aviation red or aviation white and must
meet the applicable requirements of JAR 25.1397.
(e) Light intensity. The minimum light
intensities in all vertical planes, measured with the
red filter (if used) and expressed in terms of
‘effective’ intensities, must meet the requirements
of sub-paragraph (f) of this paragraph. The
following relation must be assumed:
where:
Ie = effective intensity (candles)
I(t) = instantaneous intensity as a function of
time
t2–t1 = flash time interval (seconds)
Normally, the maximum value of effective
intensity is obtained when t2 and t1 are chosen so
that the effective intensity is equal to the
instantaneous intensity at t2 and t1.
(f) Minimum effective intensities for anti-
collision lights. Each anti-collision light effective
intensity must equal or exceed the applicable
values in the following table:
Angle above or below the
horizontal plane:
Effective intensity
(candles)
0º to 5º 400
5º to 10º 240
10º to 20º 80
20º to 30º 40
30º to 75º 20
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