DARPA’s high-speed Heliplane hits a hurdle

The Salt Lake Tribune has just run a profile of local gyroplane developer Groen Brothers Aviation. It contains a brief reference to “design issues” uncovered in September during the preliminary design review for the Heliplane high-speed rotorcraft demonstrator GBA is designing for DARPA.

GBAHeliplane%20sm.jpgSo I contacted DARPA, which said: “We underestimated the difficulty in achieving 400mph cruise performance with an existing engine and airframe. Nobody has ever flown a rotorcraft at 400mph.” Understatement – the fastest a rotor has flown sideways is 249.1mph, attached to a Westland Lynx in 1986.

GBA calls the Heliplane a “gyrodyne”: it takes off and lands like a helicopter using a tipjet-driven rotor, but cruises like an autogyro, with the rotor unpowered and thrust provided by a pair of turbofans. Gyrodynes are not new, but pushing one to 400mph is – that’s twice the speed McDonnell’s XV-1 Convertiplane tipjet compound autogyro achieved in 1956.

Designing a reaction-drive rotor system that can produce sufficient lift, generate minimum drag, carry the loads and be stable at high speed has proved to be a challenge. DARPA says GBA is working to resolve “a few remaining design issues”, then it will decide whether to proceed to full-scale windtunnel testing of the rotor system.


3 Responses to DARPA’s high-speed Heliplane hits a hurdle

  1. David Groen 30 October, 2007 at 8:04 pm #

    Hi Graham!

    This is not the first “design issue” to be uncovered. Each of the previous 5 milestone reviews have uncovered design issues which we have successfully worked through. An important purpose for the milestone reviews is to find and resolve issues if any exist. These current “issues” referred to are being attended to, with resolution expected shortly.

    As you mention, this is no easy task. However, we have on this project the most amazing rotorary-wing science and engineering team ever assembled, from academia and industry, including 5 “AHS Alexander A. Nikolsky Honorary Lectureship” award winners (including two on the DARPA team). If this can be done, and our analysis says it can, this is the team to do it.

    I must offer a correction to your comment, “[the] fastest a rotor has flown sideways is 249.1mph, attached to a Westland Lynx in 1986.” This is true for pure helicopter, but the record for the fastest rotor ever flown was the Bell 533 research project headed by Walter Sonneborn, which I believe flew at 316mph in 1972.

    I have a couple of good images of this aircraft in flight, but no way to post them here. The Bell 533 now sits outside the main gate at Ft. Eustis VA.

  2. The Woracle 30 October, 2007 at 8:18 pm #

    Hi Dave,

    Thanks for the comment, and the correction. As a fan of the Rotodyne, I hope you do overcome the issue and proceed to the next phase. And I had forgotten Bell’s compound helicopter, which can be seen here:


  3. Scott Ferrin 31 October, 2007 at 12:54 pm #

    I think it goes without saying that the harder you push the state of the art the bumpier the ride is going to be. But then that’s what makes it worth doing.

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