Book_01 Air Law

Aerodrome Lighting Chapter 21

AERODROME LIGHTS

21.1 Introduction. The profusion of lights on an aerodrome can be both confusing and
disorientating, but each light or lighting system has a purpose and most are to do with aircraft
safety. In this chapter the various lighting systems are described and their uses explained.
The learning objectives state that knowledge of lighting systems is required, but the spacing
of lights or groups of lights (excluding approach lighting systems) is outside the scope of the
course. The design of lighting systems is also beyond this course. It is an unfortunate fact of life
that there is no standard system of lighting in use although ICAO has laid down the standards
and recommended practices in Annex 14.

21.2 Aircraft Safety. A non-aeronautical light near an aerodrome which might endanger the
safety of an aircraft is to be extinguished, screened or otherwise modified so as to eliminate the
source of danger.

21.3 Elevated Lights. Elevated runway, stopway and taxiway lights shall be frangible.
Their height shall be sufficiently low to preserve clearance for propellers and for the engine
pods of jet aircraft. Where not sufficiently conspicuous, they are to be suitably marked.

21.4 Light Intensity. In poor visibility conditions by day, lights can be more effective than
marking. For lights to be effective in such conditions or in poor visibility by night, they must be
of adequate intensity. To obtain the required intensity, it will usually be necessary to make the
light directional, in which case the arcs over which the light show will have to be adequate and
so orientated as to meet the operational requirements. The runway lighting system will have
to be considered as a whole, to ensure that the relative light intensities are suitably matched to
the same end. The intensity of runway lighting shall be adequate for the minimum conditions
of visibility in ambient light in which use of the runway is intended, and compatible with
that of the nearest section of the approach lighting system when provided. While the lights of
an approach lighting system may be of higher intensity than the runway lighting, it is good
practice to avoid abrupt changes in intensity as these could give a pilot a false impression that
the visibility is changing during approach.

21.5 Intensity Control. Where a high intensity lighting system is provided, a suitable
intensity control shall be incorporated to allow for adjustment of the light intensity to meet the
prevailing conditions. Separate intensity controls or other suitable methods shall be provided
to ensure that the following systems, when installed, can be operated at compatible intensities:

 approach lighting system
 runway edge lights
 runway threshold lights
 runway end lights
 runway centre line lights;
 runway touchdown zone lights
 taxiway centre line lights

21.6 Availability. Lights may be turned off providing that they can be turned on again
within a period of 1 hour.

21.7 Emergency Lights. Normally, an aerodrome will have an alternate power supply to
cope with general power failures. Where no such back-up supply exists, emergency lights are
to be available for at least the primary runway.

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21.8 Aeronautical Beacons. Where operationally necessary an aerodrome beacon or an
identification beacon is to be provided where the aerodrome is intended for use at night. The
need for a beacon is to be determined having regard to the requirements of the air traffic using
the aerodrome, the conspicuity of the aerodrome features in relation to its surroundings and the
installation of other visual and non-visual aids useful in locating the aerodrome.

21.9 Aerodrome Beacon. An aerodrome beacon shows ‘flashes’ of light. For land aerodromes
the colours are white or white and green and for water aerodromes, white or white and yellow.
Beacons are to be provided at an aerodrome intended for use at night if one or more of the
following conditions exist:

 Aircraft navigate predominantly by visual means;
 Reduced visibilities are frequent; or
 It is difficult to locate the aerodrome from the air due to surrounding lights or

terrain.

21.10 Identification Beacon. An identification beacon is provided at an aerodrome which is
intended for use at night and cannot be easily identified from the air by any other means. An
identification beacon will show Morse code identification of the aerodrome in flashing green at
a land aerodrome (red at a UK military aerodrome) and flashing yellow at a water aerodrome.

APPROACH LIGHTING SYSTEMS

21.11 General. Approach lighting systems are patterns of fixed lights of variable intensity,
showing white, designed to give the pilot guidance to the threshold (or aiming point) of a
runway, in poor visibility or at night. The light patterns may include distance coding and give
an indication of aircraft attitude. The arrangement may also give an indication of aircraft height
above the approach plane. Systems can range in complexity from a simple centre line and cross
bar, to the highly intricate layouts associated with Cat III precision instrument approach systems.
The determination of the visual criteria for landing can be met by the visual acquisition of the
approach light system and the design must cater for the requirement of the most restrictive
decision heights and minimum descent heights. The primary unit of design is the length of
the segments, set by ICAO at 300m. ICAO requires that all the existing lighting systems not
conforming to the ICAO specification standards are to be replaced by 1 Jan 2005. Any ILS or
MLS azimuth antenna protruding through the plane of the lights shall be treated as an obstacle
and marked and lit accordingly.

21.12 Calvert Systems. Generally used in the UK and occasionally in other parts of the world,
Calvert systems (named after the inventor) consist of 5 bars and a distance coded centreline. A
NATO system is similar but doesn’t have the distance coding of the centreline.

21.13 Barrettes. The individual lights that make up the lighting systems may be arranged
either as single light units (as in the Calvert method) or in the form of groups of three or more
lights arranged as a bar (the ICAO method). For instance the centre line of a system may consist
of either single point source lights or a bar of 5 lights close together. The arrangement of 5
close together is called a ‘barrette’ (pronounced barre - et meaning small bar). They are called
barrettes so that they are not confused with the bar constituent parts of any approach lighting
system.

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Aerodrome Lighting Chapter 21

21.14 Simple Approach Lighting System. A simple approach lighting system consists of a
row of lights on the extended centre line of the runway extending, whenever possible, over a
distance of not less than 420m from the threshold with a row of lights forming a crossbar 18m
or 30m in length at a distance of 300m from the threshold. The lights forming the crossbar shall
be as nearly as practicable in a horizontal straight line at right angles to, and bisected by, the line
of the centre line lights. This type of system is used on a non instrument runway and may be
used on a non precision instrument runway.

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21.15 Precision Approach CAT I Lighting System. A precision approach category I lighting
system consists of a row of lights on the extended centre line of the runway extending, wherever
possible, over a distance of 900m from the runway threshold. If the length is less than 900m
(which on a 3° glide path coincides with CAT 1 system minima - 200 ft) it is possible that an
aircraft may not be over the approach lighting at DH. The 5 crossbars are 150m apart and form
three segments: the inner segment (0 - 300m); the middle segment (300 - 600m); and the outer
segment (600 - 900m). Any ILS or MLS azimuth antenna protruding through the plane of the
lights will be treated as an obstacle and marked and lit accordingly.

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Chapter 21 Aerodrome Lighting

Figure 21.2: Cat I Calvert 5 bar and centre line system.
Fig 15.2.3a Cat I Precision Approach Lighting System
21.16 ICAO Precision Approach CAT I Lighting System. In this arrangement, the centreline
is in the form of barrettes with only one crossbar at 300m from the threshold. Again, the
centreline should be 900m in length. The centreline may be augmented with strobe lights that
‘ripple’ towards the threshold from the start of the centreline. The visibility of the threshold
may be enhanced by the use of wing strobes (rotating).

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Aerodrome Lighting Chapter 21

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Chapter 21 Aerodrome Lighting

21.17 Precision Approach Category II/III Lighting System. At those aerodromes where Cat
II and III approaches are conducted more complex approach lighting system are installed to
enhance the possibility of the pilot achieving the visual criteria at DH to complete the landing.
The systems used are various but all are based on either the Calvert 5 bar and centreline system,
or the ICAO barrette system. Both systems should be 900m long and provide some element of
attitude information. In both the Calvert and the ICAO systems the inner segment (0 - 300m
from the threshold) is augmented by the supplementary approach lighting. This consists of
replacing the centreline of the Calvert system with barrettes and adding red wing barrettes to
both systems. The effect is to enhance the visibility and conspicuity of the inner segment. DH
for Cat 2 in not lower than 100 ft which equates to 300m from the threshold (assuming the pilot
crosses the threshold at 50 ft).

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