PP Auxilliary Power Units

Frequently, an aircraft’s auxiliary power unit (APU) generator

Fuel is normally supplied to an APU from the

An APU is usually rotated during start by

The function of an APU air inlet plenum is to

When in operation, the speed of an APU

is controlled by a cockpit power lever.
remains at idle and automatically accelerated to rated speed when placed under load.
remains at or near rated speed regardless of the load condition.

Generally, when maximum APU shaft output power is being used in conjunction with pneumatic power

pneumatic loading will be automatically modulated to maintain a safe EGT.
electrical loading will be automatically modulated to maintain a safe EGT.
temperature limits and loads must be carefully monitored by the operator to maintain a useful EGT.

When necessary, APU engine cooling before shutdown may be accomplished by

Usually, most of the load placed on an APU occurs when

Fuel scheduling during APU start and under varying pneumatic bleed and electrical loads is maintained

On APU’s equipped with a free turbine and load compressor, the primary function of the load compressor is to