Chp 3 (APU) Flashcards
What is the purpose of an Auxiliary Power Unit (APU) on aircraft?
The APU provides an auxiliary secondary power source for aircraft.
What type of engine is commonly used in most current APUs?
Most current APUs use small gas turbine engines.
What is the design type of the APU engine?
The APU engine is of a constant speed, variable torque type.
What components are used in the APU’s design?
It uses a single stage centrifugal compressor and a single combustion chamber.
What does the APU power?
The APU powers all ancillary services required while the aircraft is on the ground.
What services does the APU provide?
It provides
-air for cockpit and
-cabin air-conditioning and
-for main engine starting.
How are hydraulic and pneumatic pumps driven in the APU?
They are driven through the APU accessory drive arrangement.
Where is the APU typically located in modern passenger aircraft?
The APU is situated in a fireproof enclosure in the tail cone or rear fuselage.
How is the operation of most modern APUs controlled?
The operation is fully automatic after manual selection of the master switch and start/stop command button.
What does the APU integrated control system manage?
It manages start and close-down sequencing and governs the running RPM.
What happens in the event of a malfunction in the APU?
The APU automatically closes down in the event of
-low power,
-over-speed,
-overheating,
-loss of oil pressure,
-or a fire warning.
What is the APU fire extinguisher system similar to?
It is similar to that used for the main engines.
