Hamilton Sundstrand successfully started the first APS 5000 auxiliary power unit (APU) for the Boeing 787 on 31 October at the United Technologies-owned company’s Power Systems facility in San Diego, California.

“It started at the first attempt with the brand-new starter generator,” says business development director Karl Johanson. The new-centreline design APU is rated at 1,100shp (500kW), and drives dual 225kVA generators through a large gearbox.

Unlike previous commercial APUs developed by the company, the APS5000 is a “bleedless” design without offtakes for pneumatic systems. Power from the APU supplies the more-electric demands of the 787, which is also equipped with four additional 250kVA generators, with two units per engine.

The APU itself is also started and controlled electrically, using a system similar to that developed for the APS2300 used on the Embraer 170. “It is another application of this new technology, and eliminates another driver of the gearbox. The electric fuel pump starts before the engine is turning, and ensures that full boost pressure and atomisation is available immediately,” says Johanson.

Goodrich Turbine Fuel Technology division supplies the drive-integrated fuel injection system for the APS5000 which includes both fuel atomisers and flexible manifolds.

The APU incorporates a single-stage centrifical compressor with a pressure ratio in excess of 8:1, and a two-stage power turbine section. Other features include a low-emissions combustor and a low-noise eductor oil-cooler.

Assembly of the second test APS5000 is now under way, and one unit will be sent to Hamilton Sundstrand’s specially set up Airplane Power Integration facility in Rockford, Illinois where it will be used as part of overall tests of the aircraft’s full-up power systems.

Hamilton Sundstrand will deliver the first APU to Boeing for flight testing in April 2007. This will be on board the 787 development aircraft when it makes its first flight in August the same year. The first production APU will be delivered in October 2007.


Source: Flight International