TM 55-1520-240-23-7
9-60
LIGHTING SYSTEMS
(Continued)
9-60
FORMATION LIGHT SYSTEM WITH 17
Description
There are two formation light systems on the helicopter.
One system provides infra-red (invisible to the unaided
eye) NVG-compatible lighting. The other system
provides normal lighting for non-NVG missions. A switch
on the overhead panel selects NVG or NORM formation
lighting and a FORM DIM-BRIGHT control is common
to both systems. Each system includes four dimming
resistors, also in the overhead panel.
1.
There are eight NVG formation lights. Two are
on the aft end of the forward transmission fairing.
One is on each side between the first and second
cabin windows. One is on each side aft of the
fourth cabin window. One is on top of the pylon
and one is on the aft end of the pylon. Each light
contains two light emitting diodes connected in
parallel.
2.
The normal formation lights include five
electro-luminescent lights on top of the
helicopter. Three lights are on the forward
section of the helicopter and two lights are
side-by-side on the pylon. In the forward group,
one light is on the centerline at sta. 200, the
other two are 30 inches from the centerline on
each side at sta. 253.
Operation
1.
When the FORM switch is at NVG, power for
the eight formation lights comes from 28 volt
No. 1 dc bus. When NVG FORM LIGHTING
circuit breaker is closed, 28 vdc is connected to
the moving contact of the FORM DIM/BRIGHT
control.
2.
When the FORM control is at DIM, power is
supplied through resistors, 113R5, 113R6,
113R7 and 113R8. Rotating the switch towards
BRT drops resistor out of the circuit, until at the
BRT position power is applied directly to the
lights for maximum brightness.
3.
Power for the normal formation lights comes from
115 volt No. 1 ac bus. When FORM LIGHTING
circuit breaker is closed, 115 vac is connected to
the moving contact of the FORM DIM/BRIGHT
control.
4.
When the FORM control is at DIM, power is
applied to the lights through resistor R1. In
the next three positions of the switch, power is
applied to the lights through lower-value resistors.
At each succeeding position, brightness of the
lamps is increased. When the switch is at BRT,
power is applied directly to the lights. In this
position, the lights are at maximum brightness.
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