BOEING DEFENSE & Space Group is building an additional Heliwing unmanned air-vehicle (UAV), at its own expense, after determining in initial flight testing that the concept is feasible.
A Heliwing prototype was destroyed on 13 June during the last of nine scheduled company-sponsored flights at Moses Lake, Washington, and before entering Government-run flight tests scheduled to begin in late June.
Tom Golden, Boeing's project manager, says that the Heliwing crashed on the runway apron. An independent Boeing accident-investigation board determined the cause of the crash to be loss of engine power at the planned deceleration/descent point. A series of events resulted in significant negative engine-torque.
This condition resulted in insufficient turbine back pressure to sustain combustion and the engine flamed out. The aircraft was cleared and the engine controller will be modified.
Boeing was picked by the Pentagon's UAV Joint Programme Office to demonstrate a vertical-launch-and-recovery UAV. The Heliwing is a tail-sitter air vehicle which features a fixed wing and a pair of 2m-diameter counter-rotating propellers coupled to a single Williams International WTS117 turbine engine.
The aircraft takes off and lands in the helicopter mode. Following take-off, speed is increased in the horizontal direction while in rotary-wing mode. It then pitches/rolls over into a horizontal flight attitude.
Golden says that 99% of flight-test objectives were met before the initial Heliwing was lost. He says that Government testing will take place when fabrication of the second Heliwing is completed in ten months.
Source: Flight International
