The APU is started using what mechanism?

The APU, or Auxiliary Power Unit, in an aircraft is typically started using a DC starter motor. This system is designed to initiate the combustion process within the APU, allowing it to produce the necessary bleed air and electrical power for various aircraft systems while on the ground or during a failed engine scenario.

Using a DC starter motor is a common choice for APUs due to its reliability and efficiency in providing the power needed to start the unit. The DC starter operates by drawing electrical energy from the aircraft's battery or other DC power sources, which then engages the starter motor to rotate the APU's engine until it establishes self-sustaining combustion.

Other mechanisms might be involved in starting different types of engines or systems, but the use of a DC starter motor is specifically suited for the APU as it offers quick starts and operates within the required power specifications for typical APU applications.