TM 55-1520-240-23-7
8-57
MISCELLANEOUS INSTRUMENTS
(Continued)
8-57
A test circuit performs an overall check of the indicator.
When the selector switch is set to TEST, the indicator
pointer should go below -70ºC.
NO BREAK - WORK HARDER
The caution system includes five indicators on the
maintenance panel, three capsules on the caution
panel and seven thermal switches. Five of the thermal
switches are in temperature transmitters as follows;
forward transmission sump, combining transmission
sump, aft transmission sump, No. 1 engine transmission
sump, and No. 2 engine transmission sump. The
two remaining thermal switches are in the engine
transmission temperature switch and chip detectors,
which are mounted in the engine transmission housing.
NO BREAK - WORK HARDER
The caution system has five circuits that operate
magnetic latch type indicators on the maintenance
panel. When oil temperature in any of the five
transmissions exceeds 276º to 292ºF (136º to 144ºC)
the thermal switch closes and completes a ground
circuit to latch the indicator. When latched, the indicator
displays a black and white pattern. The ground from any
of the five thermal switches is also applied through its
associated diode to turn on the XMSN OIL HOT capsule
on the caution panel. The diodes form an OR gate that
lights the single caution capsule from any one of the five
switches while inhibiting the latching of all annunciators
on the maintenance panel when one switch closes.
NO BREAK - WORK HARDER
The caution system also has two circuits that turn on
No. 1 and No. 2 ENG XMSN OIL HOT capsules on
the caution panel. When oil temperature in an engine
transmission exceeds 375º to 425ºF (191º to 218ºC),
the thermal switch in the transmission temperature
switch and chip detector closes and completes a ground
circuit. This ground lights the associated capsule in the
caution panel.
8-159
