Technology update

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ATFI geared turbofan makes first run

Pratt & Whitney Canada (P&WC) has successfully completed the first test run of its geared turbofan engine demonstrator, the Advanced Technology Fan Integrator (ATFI).

Pratt & Whitney Canada (P&WC) has successfully completed its first test run of its geared turbofan engine demonstrator, the Advanced Technology Fan Integrator (ATFI), designed for the regional and corporate jet markets. According to the company, the ATFI demonstrator exceeded its maximum thrust target of 12,500 lb during the first run. "With the completion of this first run and with test activities now in full motion, we are looking forward to initiating the flight test program for the ATFI on our flying testbed in the coming year," said Gilles Ouimet, President and CEO of P&WC.

The ATFI demonstrator program was formally launched at the Farnborough Air Show in July 2000. The engine is being developed in close collaboration with Pratt & Whitney's Large Commercial Engines division in Hartford, CT, which has been developing geared-fan system technology for more than 10 years. Also participating as partners are MTU Aero Engines from Germany, which has been selected to supply the low-pressure turbine for the engine, and FiatAvio from Italy, responsible for the fan drive gearbox assembly, intermediate case, and accessory gearbox.

The ATFI demonstration program will enable P&WC to improve on the technology before introducing it in its new PW800 engine family, which will be in the 10,000-19,000-lb thrust range. The PW800 family will complete the company's product line by bridging the gap between the PW300 series for small regional and business jets and the PW6000 family for the 100-passenger market and above.

The PW800 engines will feature a reduction gearbox that will allow the fan to run at a slower speed than the low-spool compressor and turbine, permitting all three components to operate at their most effective speeds and efficiencies. The slower fan speed contributes to very low noise levels, while the higher turbine and LP compressor speeds lead to an engine configuration with fewer stages. With fewer parts, operating costs will be reduced.

The new engine will also feature an advanced swept-fan blade design, which brings the dual advantage of better top-of-climb performance derived from increased fan flow capacity and reduced noise levels, enabling the powerplant to meet the increasingly strict rules imposed by airport and regulating bodies.

"We believe that geared turbofans are the next big step in engine performance, efficiency, and economy," said Ouimet. "The PW800 represents a new family of environmentally friendly 'green' engines that will burn less fuel, be quieter, and require far fewer parts than current engines. Moreover, geared-fan technology can also be scaled across P&W's entire product line to meet the needs of new-generation aircraft."

- Frank Bokulich

JSF and STOVL

The VAAC Harrier during the ship-based JSF research program.

The Vectored Thrust Aircraft Advanced Flight Control (VAAC) Harrier operated by Defense Evaluation and Research Agency (DERA) has completed the second phase in the Follow-on Research Program (FRP) sponsored by the U.S./UK Joint Strike Fighter (JSF) program. The aircraft has been operating at sea with the Royal Navy carrier HMS Invincible to test aircraft control concepts applicable to the short takeoff vertical landing (STOVL) variant of the JSF. DERA stated that the first, land-based evaluation phase last year built on the results of previous trials, familiarized new pilots with the advanced control concepts of the VAAC Harrier, "and resolved known deficiencies." The major aim of the second phase has been to assess compatibility of advanced recovery modes, including novel techniques such as translational rate command applied to operations from a ship's moving deck. Two main control modes were tested with two variants of the hover positioning sub-mode, reported DERA. It was the first full evaluation of the control laws at sea. It involved UK, U.S., and Italian pilots performing 85 deck landings in various winds and sea states. One of the pilots had no previous experience in a STOVL aircraft or of shipboard operations. The shipboard operations were used to confirm the few concerns with some of the control modes that had already been raised and also allowed comparisons to be made to identify potential preferences, said DERA. VAAC Harrier Test Pilot Lt. Cmdr. Phil Hayde said the work with Invincible had demonstrated the VAAC's capability for a low workload solution that provided carefree handling and a low risk of cognitive failure. This would ease the training burden and cut costs.

The VAAC Harrier is currently at DERA's Boscombe Down site where evaluations are being performed on the STOVL automatic recovery system on the aircraft. A later phase of the FRP will research advanced control for short takeoffs and an enhancement of one of the control concepts that was investigated at sea.

The two-seat VAAC Harrier features a digital flight control system with advanced programmable fly-by-wire capabilities from the rear seat. This gives the backseat pilot full-authority digital control of the aircraft via a computer interface that allows various flying modes to be developed and installed. Also, modifications to the software and the flying experience can be achieved between flights with pilot systems and behavior comparison and feedback. The digital flight control system also offers STOVL capability without the necessity of what DERA terms "the tricky third control lever, thus, significantly reducing pilot workload." The JSF trials build on previous DERA/NASA research into advanced control laws, but the latest work incorporates the first comprehensive shipboard evaluations.

Rolls-Royce, which has more than 40 years of experience with vectored thrust technology, is involved with both airframe contenders (Boeing and Lockheed Martin) in the JSF program. Both of their concept demonstrator aircraft are powered by derivatives of the Pratt and Whitney F119 engine. The STOVL variants' propulsion systems incorporate specialist components including actuators, nozzles, and, in the case of the Lockheed Martin proposal, a remote fan to provide lift augmentation for short takeoff and vertical landing. Rolls-Royce is contracted directly to Lockheed Martin for the shaft-driven lift fan, but provides its lift devices (roll system and vectoring three-bearing swivel module) through a contract with P&W. Rolls-Royce contracts directly to Boeing for specialist equipment for the direct-lift solution favored by Boeing for its X-32B variant. Rolls-Royce is also collaborating with General Electric on an interchangeable main engine designated F120. Funding has been provided to develop the F120 as a main engine option for the JSF program. Rolls-Royce has a 40% share in the program, with responsibility for the low-pressure compressor, low-pressure turbine, combustor, and gearbox.

- Stuart Birch

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