DARPA says it plans to award Boeing Rotorcraft in Phildelphia a contract to continue its studies of the DiscRotor high-speed (300-400kt) compound helicopter concept. Little has been said about this work, but DARPA says Boeing, with Virginia Tech, has completed trade studies, design refinement, conceptual mechanical layout, windtunnel and hover-rig testing and an initial assessment of performance and flying qualities under a Phase 0 "seedling" contract.

DARPA describes the DiscRotor as having a "relatively small hub-mounted disc that can extend rotor blades to affect vertical flight". The agency's Fiscal 2009 budget documents describe it as an aircraft "equipped with a rotating circular wing having blades that can be extended from the disc edge, enabling the aircraft to take off and land like a helicopter. Transition from helicopter flight to airplane flight would be achieved by gradually retracting and stowing the blades as the circular wing assumes the task of lifting."

I can't provide you with a photograph of Boeing's concept, but I can show you a video of the seemingly similar Disk Rotor Helicopter proposed by George Vranek of Switzerland (check out his website at diskrotor.com).

DARPA says Boeing's Phase 1 contract will cover enabling technology demonstrations - including windtunnel testing of small-scale manually extendable and larger-scale automatically extendable rotor systems - to establish the feasibility of the DiscRotor concept. Additionally Boeing will refine the configuration and its performance, look at mission survivability issues, and develop options for a flight demonstrator.

The agency also says the DiscRotor program will incorporate lessons from the ill-fated DARPA/Boeing Canard Rotor Wing (CRW) program. The CRW is a high-speed rotorcraft with a two-blade, reaction-drive rotor that can be stopped in flight to form a wing, but both X-50A Dragonfly subscale unmanned demonstrators crashed while still in hover testing because of control coupling issues and the program was terminated.

DARPA is also looking at another high-speed compound rotorcraft concept, the gyrodyne, under its Heliplane program, which has been restructured and will now be led by Georgia Tech. Phase 2 of the Heliplane program will cover full-scale windtunnel testing of the rotor system, which will be powered by tipjets for vertical flight but will autorotate in forward flight, allowing speeds up to 350kt.