Boeing has restarted flight testing the A160 Hummingbird long-endurance unmanned helicopter as it prepares to offer the aircraft for the US Army's Extended-Range Multi-Purpose unmanned air vehicle requirement. Boeing acquired the A160's developer, Frontier Systems, in May.
The 80min flight on 17 September at Victorville, California, "took a big bite out of the riskiest part of the programme - the optimal-speed rotor", says programme manager Steve Glusman. The A160 is designed to fly efficiently at between 50% and 100% main-rotor RPM, whereas conventional helicopters can only operate over a narrow rotor speed range. The high-stiffness, low-weight rigid rotor can be slowed in forward flight to extend range and endurance.
Results from the flight were "very close to the analysis", says Glusman. The A160 is one of three built by Frontier under contract to the US Defense Advanced Research Projects Agency (DARPA), and the only one still flyable. The other two suffered "mechanical anomalies". The 2,000kg (4,500lb) -class A160 has an 11m (36ft) -diameter four-blade rotor and is designed for an endurance exceeding 24h and payload of more than 135kg.
Five new A160s with larger engines and improved airframes and systems will be built for further flight testing under Spiral 2 of the DARPA contract, with the first to fly next year. One will be powered by a 650shp (485kW) turboshaft in place of the modified automobile gasoline engine. "The real goal is a heavy fuel [diesel] piston engine. That gets us 24h-plus endurance," says Glusman.
GRAHAM WARWICK / WASHINGTON DC
Source: Flight International
