TM 55-1520-240-23-7
9-60
LIGHTING SYSTEMS
(Continued)
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PILOT’S FLIGHT INSTRUMENT PANEL LIGHT
SYSTEM WITH 17 AND 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, and the airspeed indicator. 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, attitude direction indicator,
and the dual engine torquemeter.
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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