VISUAL APPROACH
SLOPE INDICATOR SYSTEMS
1
It has been found impracticable to develop guidance material that will permit a
completely objective analysis to be made of which runway on an aerodrome should
receive first priority for the installation of a visual approach slope
indicator system. However, factors that must be considered when making such a
decision are:
(a) Frequency of use;
(b) Seriousness of the hazard;
(c) Presence of other visual and non-visual aids;
(d) Type of aeroplanes using the runway; and
(e)
Frequency and type of adverse weather conditions under which the runway will be
used.
2
With respect to the seriousness of the hazard, the order given in the
application specifications for a visual approach slope indicator system, 139.323(e)(1)(ii)
to (v) of Subpart H may
be used as a general guide. These may be summarized as:
(a) inadequate visual guidance because of:
(1) Approaches
over water or featureless terrain, or absence of sufficient extraneous light in
the approach area by night;
(2) Deceptive surrounding
terrain;
(b) Serious hazard in approach;
(c) Serious hazard if aeroplanes undershoot or
overrun; and
(d) Unusual turbulence.
3
The presence of other visual or non-visual aids is a very important factor.
Runways equipped with ILS or MLS would generally receive the lowest priority
for a visual approach slope indicator system installation. It must be
remembered, though, that visual approach slope indicator systems are visual
approach aids in their own right and can supplement electronic aids. When
serious hazards exist and/or a substantial number of aeroplanes not equipped
for ILS or MLS use a runway, priority might be given to installing a visual
approach slope indicator on this runway.
4 Priority should be given to runways used by
turbojet aeroplanes.