TM 55-1520-240-23-7
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LIGHTING SYSTEMS
(Continued)
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PILOT’S FLIGHT INSTRUMENT PANEL LIGHT
SYSTEM WITH 17 AND WITHOUT 74
Description
The pilot’s instrument panel light system includes a
PLT INST LTG control, 0-115 volt variable transformer,
115 to 5 volt autotransformer, and lamps to light
the instruments and the RAD ALT dimming panel.
Panel lights light the following instruments: cruise
guide indicator (CGI), rate of climb, AIMS altimeter,
rotor tachometer, airspeed indicator, and the dual
engine torquemeter. Internal lights light the following
instruments: turn and slip indicator (lightplate), RAD
ALT DIM attitude indicator, horizontal situation indicator
(HSI) and mode select panel (lightplate), radar altimeter,
and attitude direction indicator.
NO BREAK - WORK HARDER
The pilot’s clock is lighted by a 28 vdc circuit.
Operation
Power for the 5 vac system comes from the 115 volt No.
2 ac bus. When the PILOT INSTR LIGHTING circuit
breaker is closed, 115 vac is applied to the PILOT INST
LTS control which varies the 5 volt output to vary the
brightness of the lamps. When the control is turned
from DIM, a switch arms a circuit in the secondary
lighting circuit which turns on the floodlights in an ac
power failure, and also provides dimming for pushbutton
lighting in the cockpit.
NO BREAK - WORK HARDER
When the PLT CLOCK circuit breaker is closed, 28 vdc
from No. 2 essential bus is routed to the clock.
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