New Engine for New Airplane: AlliedSignal Wins a Perfect Fit

It is a sign of the pace of development in the business aircraft market that Allied Signal's AS900 engine, which was a quiet internal demonstration effort at the time of last year's NBAA convention, is here as a full-scale development program. Allied Signal announced the launch of the all-new engine at the Farnborough Air Show in September.

By the end of this week, if industry buzz is correct, Bombardier will have announced the selection of the AS900 to power a new BD-100 "super midsize" business jet.

"This is the biggest single investment within Allied-Signal," commented Allied-Signal Engines president Steven Loranger, "and we are launching in great confidence that the market needs it."

The first version of the AS900 will be rated at 7,500 pounds thrust, says Dominique Hedon, vice-president for commercial production. The company has been working seriously on the engine for some time: Major components, including the high-pressure compressor, high-pressure turbine and combustor, had been rig-tested a year ago, and a complete core ran early this year. The first full engine will run in July 1999, and it is scheduled for certification in the first quarter of 2001.

Taiwan's AIDC, a long-term partner with AlliedSignal on the F124/F125 military engine family, will produce the AS900 fan module, accounting for 14 percent of the engine's value. Another risk-sharing partner - as yet unannounced -- is discussing an equal stake, and smaller partners may take another 6 percent, leaving a total of 34 percent of the program with partners.

AlliedSignal's aim from the outset has been to provide not only competitive performance, but the "highest possible thrust per dollar cost of ownership", says Hedon. The goal is to beat the ownership cost-acquisition, fuel and maintenance of present-day engines by 30 percent. Integrated product teams are designing every part of the engine to meet that goal, using technologies such as large one-piece castings, integral blades and rotors, and high-work turbines with a minimum number of blades.

In some cases, the most advanced technology was bypassed because it did not provide the customer with an economic benefit, said Hedon. "We don't start with the technology, but with our VOC [voice of the customer] process. It's different from a few years ago, when you'd put technologies together into the nicest engine you could do." For example, there are design features that provided "an impressive reduction" in the number of parts in the engine, "but when we did the trades, added to the cost and weight of the engine. We found that there were other ways to skin the cat that were more efficient."

Another example of the importance of cost can be found in the core's basic thermodynamics: the engine uses a high-efficiency axial-centrifugal compressor to meet performance goals at modest temperatures. This makes it possible to design a durable combustor and turbine which are less expensive to build and to maintain.

Loranger adds that while cost has always been an essential element of any engine design, this is the first time that it has been treated as a priority, and identified as the factor that will differentiate a new engine from its competition.

The AS900 can grow to 9,000 pounds thrust with a larger fan and added booster stages, says Hedon, and the family is also designed to reach down to 4,000 pounds -- versions below 5,500 pounds will have significant core changes.

Apart from a new business jet, early applications include an updated version of the Avro RJ four-engined regional airliner.

By Bill Sweetman