The purpose of an aircraft Auxiliary Power Unit (APU) is to provide energy for purposes other than propulsion - most often to operate a generator for electrical power. Although small piston-engine APUs were first used in aircraft on a limited basis during World War I, it was in World War II that they came to be used extensively on large aircraft.

In 1963, the Boeing 727 became the first jet airliner to use a gas turbine APU for power.

The Auxiliary Power Unit (APU) on display in the Museum, courtesy of Dallas Airmotive, is typical of the type found on a modern business jet. This non-functioning generic example is made up of parts from various APUs and therefore, is not a specific make or model from any one manufacturer.