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Aviation History
1994
1994 - 0074.PDF
Pratt & Whitney Canada (P&WC) occupies a unique position among auxiliary power-unit (APU) man ufacturers. It builds the West's most powerful APU, the PW901A, for the world's largest airliner, the Boeing 747- 400, but the Canadian company has found it difficult to convert that premier position into market leadership. Today, six years after P&WC delivered the first PW901A to Boeing, it remains the company's only APU product. The l,050kW (l,400shp) PW901A has been a technical and financial success for the company — and its customers. That success has, perhaps belatedly, been re cognised by an increased focus within P&WC on APUs as a product line sepa rate from P&WC's propulsion engines. Ian Matthews, marketing manager for the company's recently formed APU prod ucts unit, says that 20% of P&WC's expenditure for research and development is on APUs, which account for only 5% of the company's sales. The money is being spent on finding new applications for the PW901A and in defining a companion APU for smaller widebody aircraft. P&WC's chance to enter the APU marketplace came in October 1985, when Boeing launched the 747-400 and decided to hold a competition to supply the APU — Garrett (now AlliedSignal Engines) having supplied the APUs for all previous models of 747. Boeing wanted an APU based on a proven engine and it wanted prototypes by December 1987. P&WC submitted a proposal early in 1986, based on its JT15D small turbofan. The PW901A had a promised fuel con sumption 40% lower than that of the existing Garrett design and a contract to supply the APU as standard equipment on the 747-400 was signed in June 1986. P&WC took the JT15D's core and added a new power turbine to drive the load compressor and gearbox. A demon strator engine was run for the first time in June 1987 and the first complete engine was run in December 1987. Flight- certificated APUs were delivered to Boeing in January 1988, ready for the roll-out of the first 747-400 at the end of that month. From initiation to certification, the project took just 27 months. "It was a most challenging programme — the shortest Pratt & Whitney Canada has done," says Matthews. Despite some early teething troubles, he says that, within two years of the 747-400 entering service in 1989, PW901A reliability was "equivalent or better than" that of the Garrett APU in earlier 747s, he says. Increased reliability, lower fuel con sumption and longer life are benefits claimed for the PW901A. Most are a result of the APU's two-spool design: the PW901A has separate, counter-rotating, gas-generator and load-compressor spools. AUXILIARY Pratt & Whitney Canada builds the West's W \ ^^"^^ f**\ most powerful auxiliary power unit (APU), L^r m • ^^^ the PW901A, yet it remains the company's W m . ^j only APU product. Graham Warwick «^^ ^-^ ^-^ describes the unit and reports on the company's efforts to step up its presence in the APU market. 24 FLIGHT INTERNATIONAL 12 - 18 January. 1994
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