Here is the latest Groen/DARPA Heliplane configuration. The proposed demonstrator is based on an Adam A700 very light jet. Air from the twin Williams FJ44 turbofans is ducted to the rotor tips, mixed with fuel and burned to drive the rotor for vertical take-off and landing (remember the Fairey Rotodyne). In forward flight, at speeds up to 400mph (they hope), the rotor would autorotate like an autogyro. The notional mission around which the demonstrator is being designed is combat search-and-rescue.
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