APU- PW900

The PW901A is an Auxiliary Power Unit (APU) designed and developed to provide pneumatic power for main engine start and cabin environmental control. It also has drive pads for two airframe supplied generators that provide electrical power to the airplane. This APU, which is used on the Boeing 747-400 aircraft, is also suitable for marine applications.

Main engine components include: a gas generator section that incorporates a single-stage centrifugal compressor driven by a single-stage turbine, an annular reverse flow combustor with 14 air-blast fuel nozzles and dual high energy igniters, a Full Authority Digital Electronic Control (FADEC). a single-stage load compressor driven by a single-stage turbine, and a load gearbox that incorporates mounting pads for two 90 kVA AC generators.

Operation
Gas generator and load compressor air enter the engine through a common inlet. The former is directed to the gas generator compressor impeller, where it is compressed and passed through diffuser pipes to the combustion chamber. There it is mixed with fuel and ignited. The resultant hot gas energy drives both the high and power turbines before exiting via the exhaust duct. The load compressor air is directed to the load compressor impeller and then passes through a diffuser assembly to the diffuser duct, where it is used for aircraft pneumatic services.

Pratt & Whitney Canada Corp., 1000 Marie Victorin Blvd, Longueuil, PQ J4G 1A1. Tel: 800-268-8000; Fax: 450-647-7588.