AUXILIARY POWER UNITS (APU) Flashcards
What is the typical relationship between an aircraft‘s auxiliary power unit (APU) generator and the enginedriven generator?
They are identical.
Where does the APU fuel supply normally come from?
The airplane’s main fuel supply
How is the APU rotated during start up?
With an electric starter
What is the function of an APU air inlet plenum?
It is to stabilize the pressure of the air before it enters the compressor.
When operating at high loads, what is the speed of an APU?
The APU remains at or near rated speed regardless of the load condition.
What is the effect of the pneumatic power when being used in conjunction with maximum APU shaft power
output?
The pneumatic loading will be automatically modulated to maintain a safe EGT.
Before shutdown, how would APU cooling be accomplished?
By closing the bleed air valve
When is most of the load placed on an APU?
When the bleed air is opened
What regulates fuel scheduling during APU start and under varying pneumatic bleed and electrical loads?
Fuel scheduling is maintained automatically by the APU fuel control system.
What is the primary function of the load compressor on APUs equipped with a free turbine and load
compressor?
To provide bleed air for aircraft pneumatic systems.
