Engines
Auxiliary power unit
apu, Auxiliary Power Unit
At a glance
Meaning of Auxiliary power unit
A small gas turbine providing electrical power, air or engine-start support.
More about Auxiliary power unit
An APU supports aircraft systems, particularly on the ground, without requiring the main engines to run. Its exact capabilities depend on the installation.
It is not a main propulsion engine. Availability and permitted use vary with the aircraft's operating conditions and procedures.