-as Allison begins JSF lift-fan tests

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LIFT-FAN HARDWARE for Lockheed Martin's short-take-off/vertical-landing Joint Strike Fighter (JSF) variant is arriving at Allison Advanced Development, which plans rig tests before delivering a complete lift fan to Pratt & Whitney in August 1998.

P&W will integrate the shaft-driven lift fan with its F119-based SE611 engine for ground tests leading to a Ìrst flight in Lockheed Martin's JSF concept-demonstrator aircraft in May 2000.

Allison programme manager John Schroeder says that tests of the lift fan's "D" nozzle are under way at NASA. The nozzle vectors the fan's 82kN (18,500lb) thrust from 15 degrees forward to 60degrees aft of vertical. A 30%-scale model is being tested to correlate the nozzle's thrust co-efficient and angularity with predictions made by computational fluid-dynamics. "The initial correlation matches well," he says.

Allison parent company Rolls-Royce is developing the fan module, which consists of a two-stage, counter-rotating fan with variable guide-vanes to modulate thrust. Airflow, surge margin and aerodynamic efficiency of the fan will be validated in rig tests before delivery of the lift fan, Schroeder says.

Rig testing is also planned for the Allison-developed gearbox, which will transmit up to 20,000kW (27,000hp) from the engine to the fan via bevel and pinion gears, and the dry clutch, which will absorb up to 6,000kW when the fan is engaged. A single-stage, 8,950kW prototype of the lift fan was successfully tested in 1995-6 on Lockheed Martin's Large Scale Powered Model, a forerunner of its JSF design.