Abstract :
The auxiliary power unit serves as a source of electric current when the aircraft
starts the engine, the structure of the auxiliary power unit consists of several
components such as the gear box, compressor and turbine (hot section), the work
process of the auxiliary power unit (APU) utilizes outside air. to be used as a
mixture of the combustion system, which is converted into high pressure in the
combustion chamber, with the help of a turbine booster to suck in outside air.
A failure occurs in the process of the air inlet door in the form of a problem
with the actuator, usually due to leakage or damage to the components inside the
actuator which causes the actuator to not operate, which results in some components
also failing during operation, such as ram air inlet bam that cannot be opened or
closed. .
There is damage to the actuator, namely in the electric motor, because due to
the low insulation resistance, the insulation resistance from the electric motor
windings will decrease over time, as long as the electric motor is working, the
resistance value will decrease to the lowest limit until the electric motor does not
allow it to work, which affects low performance Insulation resistance is the
environmental temperature factor. After seeing the problem, do the troubleshooting,
according to the procedure from AMM (Aircraft Maintenance Manual) and FIM
(Fault Installation Manual) ATA 49-15-31 task 405. Attempts are made to
overcome problems that cause malfunction of the air entrance by replacing
actuators.