How long is a typical APU cool-down period?
Three minutes
How is an APU's operating speed maintained despite variations in the loads imposed?
By the APU's fuel control automatically adjusting the fuel flow.
How is the cool-down for many APU's accomplished prior to shutdown?
By running the APU for a specified minimum period of time after closing the bleed air valve (unloaded)
What is the operating effect of following a required cool-down period prior to APU shutdown?
The APU's EGT is lowered and stabilized
Name atleast two uses for APU produced pneumatic power?
Engine starting, ground air conditioning, anti-icing
What is the usual source of a gas turbine APU's fuel supply?
One of the aircrafts main fuel tanks
What usually places the greatest demand on a gas turbine APU?
Bleed air loads
What is the function of an APU on modern transport category aircraft?
To supply ground electrical and pneumatic power to aircraft systems when the engines are not operating, and in some aircraft as a backup source of inflight electrical power.
What does a typical APU consist of?
A small turbine powerplant with provisions for supplying bleed air, and an electrical generator that is usually identical to those mounted on the aircrafts engines.
What is typically used to start an APU?
Its own electric starter and battery power.
At what speed does a gas turbine APU operate?
An APU operates at or near its rated speed regardless of the electrical or pneumatic loads imposed.