RUNWAY AND TAXIWAY LIGHTING
9.1 INSET LIGHTS
General
9.1.1 It is advisable that inset light fittings have a
minimum vertical projection above the surrounding surface consistent with the
required photometric characteristics and a minimum bulk above the surrounding
surface consistent with presentation of an easy slope in all directions. They
should be capable of withstanding the greatest tire pressure and weight of the
heaviest type of aircraft expected. Regard should also be paid to the speed which
aircraft may attain on that part of the movement area in which inset lights are
to be provided; the permissible extent of the projection of a light fitting
suitable for marking the centre line of a taxiway (other than a high speed
turn-off) would be greater than could be tolerated for a runway inset light.
Installation
9.1.2 Installation of touchdown zone lights of the
shallow inset type and runway centre line lights is accomplished by drilling a
hole into existing pavement slightly greater in depth than the fitting. A
sufficient quantity of sealant material is poured into the prepared recess hole
and the fitting is installed to proper alignment and elevation by means of a
jig or holding device.
9.1.3 Slots or saw kerfs approximately 3 cm deep and a
minimum of 0.60 cm in width are provided in the existing pavement which connect
a specified number of light recess holes and extend to the runway edge. Small
diameter wires are laid into the slots and filled with sealant material.
9.1.4 Installation of touchdown zone and centre line
lights of the deep inset type is accomplished as part of pavement construction.
A properly sized hole is left open during the initial paying to accommodate the
subsequent installation of three inset bases for a barrette. A rigid conduit is
placed below the pavement from the edge of the runway and connected to the
inset bases. The three inset bases are held at
the proper elevation and alignment by means of a jig. The open area is then
backfilled with concrete pavement. Wire is drawn through the conduit into the
bases, connexions are made to insulating transformers and the removable top
fitting, containing the lamp, is bolted onto the inset base to complete the
installation.
9.1.5 Techniques for installation of deep base cans in
existing concrete pavement are also available. The advantage of using deep can
and conduit installation is that the maintenance of lighting is less expensive
and much more rapid. At busy airports the ability to make rapid repairs is of
great importance.
Measuring the temperature of inset lights
9.1.6 The following paragraphs provide guidance
material on in-service and laboratory methods for assessing the temperature of
inset lights.
Effect of
inset lights on tires
9.1.7 Concern has been expressed that the possibility
may exist whereby in-service tires may be damaged by heat from inset lights.
Tests have been undertaken by a number of States to measure the temperature of
inset lights and the effect on tires both in contact with and close to the
lights. Results have indicated that where the tire is in contact with an inset
light, temperatures of up to 16WC for a short period of time (i.e. about 10
minutes) have not caused any, significant damage to the tire. Also the radiant
energy, in the light beam from inset lights can give rise to high tire
temperatures but again to date it has not been found to cause any significant
detrimental effects on the tire.
9.1.8 One reason that the heat from inset lights has
not been a problem is that the high temperature on the top of the inset light
is very localized, i.e. usually in the centre of the top of the inset light.
There is generally a large temperature gradient between the centre and the edge
of an inset light and it could be that the total energy absorbed by the tire from
the inset light is relatively small.
Difference between field and laboratory tests
9.1.9 Several States have undertaken field studies to
investigate these effects. Additionally, laboratory-based studies where the
tests have been made in a draught-free, heat test chamber have been conducted.
It is significant that the laboratory temperature measurements are considerably
higher than those experienced in the field. This fact is well known as the
influence of any air movement has a considerable cooling effect on the object
being investigated.
Recommended temperature limits
9. 1. 10 Based on current knowledge, the two sets of
conditions under which measurements can be made, field and laboratory,
necessitate stipulating figures appropriate to each. The laboratory -based
measurements will be repeatable whereas the field measurements will be somewhat
variable. In view of the limited knowledge available concerning the effects of
very high ambient temperatures combined with strong solar radiation on tires,
runway surfaces, inset lights, etc., it is suggested that for these areas,
individual recommendations may be required and possibly some operational
safeguards may be necessary. and the inset light
should not exceed 16WC during 10 minutes of exposure, whether by conduction or
radiation. The inset light should he operated at full intensity for a
sufficient time prior to the measurement for the light to reach a temperature
approximating to thermal equilibrium. This time would probably be at least two
hours. The measurement should be made using a thermocouple placed between the
surface of the tire and the part of the inset light which is heated the most.
For some designs of inset lights the temperature at the surface of the tire can
he a maximum due to radiant energy in the light beam and therefore a series of
measurements may have to be made to ascertain the most critical position.
Laboratory measurement method
Field conditions
9.1.11 For tests undertaken on installed inset lights,
the temperature at the interface between the aircraft tire
9.1.12 For tests undertaken under laboratory
conditions, it is suggested that the temperature at the interface between the
inset light and the tire should be not more than 16WC during 10 minutes of
exposure, whether by conduction or radiation. These tests should be undertaken
in a draught-free, heat test chamber where the temperature of the ambient air
is 3TC. Before the measurements are taken, the inset light should be operated
at full intensity for a sufficient time for the light to reach a temperature
approximating to thermal equilibrium. This time would probably be at least two
hours.
9.1.13 For these tests the inset light should be
placed in a box of the minimum dimension shown in Figure 9-1. The box could be
either:
(a)
concrete, with the inset light bonded into the concrete in the way recommended
by the manufacturer; or
(b)
sand-filled.
It
should he noted that the sand-filled box will give rise to the more onerous
conditions for testing due to the low thermal conductivity of the sand.
9.1.14 In most cases the measurement should be taken
when the tire is directly on the inset light and the thermocouple lies between
the tire and the hottest part of the inset light. However, for some designs of
inset lights, the temperature at the surface of the tire can be a maximum due
to radiant energy in the light beam and therefore a series of measurements
should be made to ascertain the critical position. The tire should be
sufficiently loaded so that during the test the contact between the tire and
the inset light is properly representative of service conditions.
9.2 TAXIWAY EDGE LIGHTS "
9.2.1 At many airports, the concentration of taxiway
edge lights in the operational area often results in a confusing mass of blue
lights commonly referred to as a "sea of blue". Most of the older
airports have added or extended taxiways but, at the same time, have kept
active all the old ones. It is quite normal for all of these taxiway lights to
be turned on at the same time which adds to the confusion.
9.2.2 This problem can be considerably reduced by any
of the following methods:
(a)
selective switching;
(b)
use of centre line lights; or
(c)
use of lamp shielding.
9.2.3 Selective switching is a process wherein only
the edge lights on the taxiway in use are energized. This method requires
additional control and switching equipment, and its effectiveness would depend
on the configuration of taxiways at each particular airport.
9.2.4 The use of green centre line lights, in lieu of
edge lights, on straight sections of taxiways would also reduce the problem.
However, this method has the disadvantage in
that the flush centre line lights are more expensive than edge lights.
Furthermore, edge lights are normally installed with the centre line lights on
curved portions of taxiways.
9.2.5 The use of shielded blue edge lights may be the
less expensive method to alleviate this problem. One method of shielding is the
use of special lamps which have an opaque coating applied directly onto the
glass envelope. Other methods involve the use of mechanical shields attached to
the outside of the lens or reflectors fitted and installed inside the lens. The
latter two methods have the advantage of permitting the shields to be adjusted
to suit any location.
9.3 EXIT TAXIWAY LIGHTING
9.3.1 The Annex 14, Volume 1
specifications for runway centre line lights and taxiway centre line lights
were amended to include lateral tolerances of
9.3.2 It is important to note that the specifications
still envisage the display of the runway centre line marking and taxiway centre
line marking along the centre line of the runway and taxiway, respectively.
Where the lights are located on the marking and where the marking is applied using
a machine, the light fittings should be covered with paper or the machine
temporarily deactivated to avoid the lights.
9.3.3 Of the four conditions illustrated in Figure
9-2, condition a) is the simplest. The runway consists of a flexible pavement
(e.g. asphalted concrete) and consequently there is no difficulty in installing
the runway centre line lights along the centre line of the runway or the exit
taxiway centre line lights on the exit taxiway centre line marking.
9.3.4
Condition b) represents a cement concrete runway with a longitudinal joint
along the runway centre line. As a result, the runway centre line lights are
offset by
9.3.5
Condition c) represents a case where exit taxiways are located on both sides of
a runway which consists of a flexible pavement, e.g. asphalted concrete. The
runway centre line lights are located along the runway centre line and the exit
taxiway centre line lights on the exit taxiway centre line markings.
9.3.6
Condition d) represents a case where exit taxiways are located on both sides of
a cement concrete runway. The runway centre line lights are offset by