VISUAL APPROACH SLOPE INDICATORS
(VASI)The VASI system provides the pilot with
visual approach slope angle information while on final
approach. The VASI system is helpful during daylight
or night operations. There are three standard VASI
system configurations: VASI-4. VASI-12, and VASI-
16. We will discuss the VASI-12 system as it will
appear on most Navy airfields.
The VASI system consists of twelve light boxes
with three lights in each box. There is one complete
system for each end of the runway. There are two pairs
of bars-one pair of bars on each side of the runway.
Each wing bar is composed of three light boxes (fig.
6-36). The set of bars nearest the threshold is called the
downwind bars. and the other pair. the upwind bars.
Each light box projects a beam of light that is white
(clear) in its upper part and red in its lower part. The
lights are arranged so that the pilot of an airplane,
during the approach. sees all of the wing bar lights as
red when below the glide slope. When on the glide
slope. the pilot sees the downwind bar lights as white
and the upwind bar as red. When above the glide slope,
the pilot sees all the wing bar lights as white.
FRESNEL® LENS OPTICAL LANDING
SYSTEM (FLOLS).Another system designed for
continuous automatic operation is the FLOLS. (See
fig. 6-37.) It also provides optical landing assistance
by indicating the correct glide slope angle to the pilot of
an approaching aircraft. This system contains two
groups of horizontal datum lights set perpendicular to
the approach path; two vertical bars of wave-off lights;
two double types of cut lights; and a source light
indicator assembly, consisting of five vertical cell
assemblies. Each cell assembly contains source lights,
a Fresnel® lens. and a lenticular lens. The arrangement
of these lenses gives the pilot the glide slope. The unit
should be set up on the left side of the runway, from the
pilots perspective, about 10 feet from the edge of the
pavement and 750 feet from the runway threshold.
Power for the system is provided by an installed
field lighting supply or by an auxiliary, power unit
capable of 20 kilowatt (kW). 60 hertz (Hz), three-
phase, 120 volts phase to neutral.
RUNWAY DISTANCE MARKER.With the
use of high-speed aircraft, the runway distance marker
system is needed to tell the pilots how much runway is
left to take off or to land. The distance information, in
thousands of feet, is given by numbers on the side of the
marker. The numbers are on two sides of the signs, so
that the distance left can be shown for both directions.
There is one row of signs on each side of the runway.
Each row is the same distance from the runway center
Figure 6-36.Visual approach slope indicators (VASI).