Boeing has suspended flights of its A160 Hummingbird after the 10 December crash of the long-endurance unmanned helicopter at Victorville in California. The cause of the crash is not known.

The turbine-powered A160T, vehicle A008, was flying at 5,000ft (1,500m) above mean sea level - about 2,300ft above the ground - before it crashed and was destroyed, the company says.

A Boeing-led accident investigation team is being formed and flight operations have been suspended until the cause of the crash has been determined. The vehicle was one of three A160s on flight status at Victorville, says Boeing.

 Boeing A160T in flight
© Boeing

The A160T made its first flight in June and had completed nine flights. It is the first crash of the turbine-powered Hummingbird, but the earlier gasoline-engined A160 has crashed three times in 36 flights since January 2002.

Development work on the unmanned helicopter has been funded by the US Defense Advanced Research Projects Agency and Special Operations Command.

Boeing says it has a second A160T at its facility in Irvine, California facility that is configured for flight, but is being used as a ground test vehicle. The A160T is powered by a Pratt & Whitney Canada PW207 turboshaft.

The Hummingbird is equipped with an optimum-speed rotor that can be slowed by up to 50% to extend endurance. The rigid rotor system and lightweight, low-drag airframe are also designed to enable ranges up to 2,500nm (4,600km) and ceilings up to 20,000ft.

Boeing is aiming to demonstrate at least 18h endurance with the A160T and says the UAV is designed to exceed 24h with a 135kg (300lb) payload. The unmanned helicopter completed a 12h flight in October.