Pratt & Whitney has started assembly of its geared turbofan demonstrator that will begin ground tests in November.

The assembly of the first GTF, which will fly on P&W's Boeing 747SP testbed around mid-2008, comes as the company reveals new details about the geared design and the part it will play in its ambitious common core architecture plan.

This initiative forms the basis for a range of new engines to tackle everything from the 10,000lb-thrust (45kN) range new business jet engine to the 30,000lb- class next-generation Airbus and Boeing single-aisle products. P&W hopes the plan will form the platform for generations of engines.

Using a baseline high-pressure core design, the company plans to develop a "flexible scaling strategy" to suit varying thrust requirements, including Bombardier's proposed CSeries airliner. "We're looking at defining a scaleable core. So what that says is within a range of core sizes we will have the capability of scaling it up and scaling it down," says engineering senior vice-president Paul Adams.

Although the GTF demonstrator is based on a PW6000 core, production versions will be based on one member of the new scaleable core family. On the GTF, Adams says: "We've already had the gear drive system delivered by Avio, and we will be testing the high-speed low-pressure compressor in May on a rig, in parallel with the build-up process. The low-pressure turbine is also in work and by June we will have all the hardware delivered," he adds.

Core build-up is taking place at the company's Middletown assembly site in Connecticut.

Tests on the advanced lubrication system, which includes back-up oil systems capable of working in zero and negative g conditions, have also taken place. Tests were conducted last December using a lube rig mounted in the cabin of the company's Boeing 720 testbed. The flights, which briefly created zero and negative g conditions, were "very successful", says Adams. "We're pretty confident we got steady state oil delivery."

Tests of the GTF are aimed at positioning P&W for the launch of a full-scale development programme in late 2008 with entry into service possibly as early as 2012. Although Airbus and Boeing have indicated a potential 2014-15 launch window for the next-generation single-aisle aircraft, this does not detract from P&W's strategy, says company president Steve Finger.

"I don't think any of us know exactly when the new small aircraft will occur. P&W's job is not to second-guess timing. Our job is to make sure that when the market is ready we'll be there," he says.

Source: Flight International