TM 55-1520-240-23-7
9-125
MISCELLANEOUS EQUIPMENT
(Continued)
9-125
APU ELECTRONIC CONTROL UNIT (ECU)
The control unit is on the left side at sta. 502. Helicopter
wiring is connected to the unit components through two
connectors and receptacles. The control unit controls
APU starting and operation. It also monitors the APU for
overtemperature, overspeed, underspeed and the ECU
internal circuits. Should a malfunction occur during start
or while the APU is operating, the ECU will automatically
shut down the APU. Four built in BITE indicators are
located on the receptacle end of the ECU without
33 and give a visual indication of failure mode.
POWER STEERING CONTROL BOX
The power steering control box is part of the power
steering system. The control box is located in the
console and is used to steer the helicopter while ground
taxiing. When the SWIVEL switch is set to STEER
and STEERING CONTROL knob is turned left or right,
power is applied to a servovalve on the aft right landing
gear which causes hydraulic pressure to flow to the
power steering actuator which in turn cause the wheel
to move left or right. This system eliminates the need
to make pedal turns while ground taxiing. Power for
the steering control box is from HYDRAULIC BRAKE
STEER circuit breaker from the 28 vdc No. 1 bus. The
control box is connected to helicopter wiring through a
connector and receptacle.
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