The Pentagon's Defense Advanced Research Projects Agency (DARPA) has teamed with Frontier Systems to flight test a revolutionary unmanned helicopter that can stay airborne for as long as 62h and achieve an unrefuelled maximum range of 8,550km (4,600nm).
The newly revealed long endurance unmanned helicopter and the rival Boeing canard rotor/wing (CRW) are part of DARPA's Advanced Air Vehicle advanced technology demonstration.
The A160 Hummingbird vertical take-off and landing unmanned air vehicle was conceived by California-based Frontier.
Initially, the helicopter is being developed as an unmanned drone to reduce cost and risk, but David Whelan, director of DARPA's tactical technology office, believes that the technology can be applied to manned helicopters. The A160 features a hingeless, rigid rotor providing low disk loading and low rotor tip speeds, thereby increasing endurance dramatically.
The first year of the 36-month jointly funded research effort will be devoted to ground tests and flight control development, Whelan says. A flight test programme would get under way at the end of 1999.
"This effort pushes basic fundamental aerodynamic flight vehicle science to see if we can do new things with helicopters. The basic goal is to develop an optimum performance helicopter across a wide envelope of rotational speeds," Whelan says.
Rotorcraft manufacturers will have to rethink their performance goals if the demonstration is successful. "Why settle for a helicopter with 6h endurance when you can have one with 40h endurance for the same cost?" Whelan adds.
Meanwhile, Boeing and DARPA are each contributing $12 million to demonstrate the Boeing-patented CRW concept for both manned and unmanned applications.
Over the next three years, Boeing Phantom Works will design, build and fly two technology demonstrators able to fly at speeds in excess of 375kt (690km/h).
The aircraft takes off and lands like a helicopter, and uses the stopped rotor as a wing in forward flight. The Williams International F412 turbofan powers the reaction drive rotor in helicopter mode and provides forward thrust in aeroplane mode.
Source: Flight International
