Huffer

For information about the form of substance abuse known as huffing, see inhalant. For the Transformers character, see Huffer (Transformers).

In aviation, a huffer is an external engine that creates large volumes of pressurized air used to start large gas turbine jet engines on some types of aircraft.

The huffer works by blowing compressed air via flexible hose to the aircraft's bleed air system. From there, the air flows via a pilot controlled valve to the engine's starter motor. The starter motor converts the energy of the moving air to rotational torque. The starter motor is linked via shaft to the N2 or core of the engine and spins the compressor and first stage turbine. Once there is enough air flowing through the compressor and the combustion chamber to light the engine, fuel in the form of vaporized kerosene starts flowing and an igniter similar to a spark plug ignites the fuel. Then fuel flow is increased to spin the engine up to its normal idle speed, at which point the engine is self-sustaining and no longer needs the support of the starter.