It appears DARPA is scaling back ambitions for the Heliplane gyroplane program while taking a closer look at another high-speed rotorcraft concept. The agency'has'awarded Boeing a $7.35 million contract for Phase 1 of the DiscRotor risk-reduction study. The DiscRotor is a compound helicopter'with a rotating circular wing that can extend and retract rotor blades depending on the phase of flight.
DARPA thinks the DiscRotor should be capable of 400kt-plus at 30,000ft, while retaining the hover and low-speed characteristics of a helicopter. The rotor blades are extended for vertical flight and gradually retracted and stowed during the transition from helicopter to aeroplane mode. The disc is stopped and acts as a circulation-control wing in forward flight.
Under Phase 1, according to earlier DARPA documents, Boeing's advanced rotorcraft folks in Philadelphia will conduct windtunnel tests of a small-scale manually extendable rotor followed by a larger automatically operated system. The focus will be on the transition'between rotor- and disc-borne flight. Boeing and teammate Virginia Tech conducted concept definition studies under a previous phase.
Boeing has experience with circulation control from its work on the ultimately unsuccessful X-50A Dragonfly Canard Rotor/Wing demonstrator. A first glance, it looks like it might be easier to get the DiscRotor to work than the stopped-rotor X-50. And what about Heliplane, DARPA's previous best bet for high-speed VTOL?
No-one is saying'anything yet, but while DARPA has awarded Georgia Tech a contract for the next phase of the program it looks likely a flying demonstrator is no longer on the cards. Last July the agency announced plans to shift leadership of the program from struggling Groen Brothers and award Georgia Tech a contract'to close the design and experimentally demonstrate the ability to to control the VTOL gryoplane at speeds up to 400mph.
That is likely to involve a windtunnel test of the rotor system. A key goal will be to demonstrate the reaction-drive rotor can meet tip-jet noise requirements. This is an'area where Georgia Tech came to Groen's aid during Phase 1 of program, which was extended six months to give the team more time to come up with a new design for the blade-tip jets. DARPA thinks they did - the tests will tell."