The propfan vectored slipstream VSTOL (Vertical and Short Lift-Off) integrates the technologies for a high-speed propfan airliner with high-lift technology applied to vectoring the slipstream of a propeller or propfan through angles of 80 to 90 degrees to provide the best configuration for a transport aircraft that can take off and land vertically and cruise efficiently at 400 to 450 knots. An usable payload-gross weight fraction in a VTOL aircraft becomes particular difficult to achieve as the size of aircraft increases. Studies of various approaches for a high-speed 400-450 knot 120 passenger VSTOL transport and its military version led to the conclusion that vectoring the slipstream and using a high disc loading propulsion system provides a higher payload gross weight fraction for a large VSTOL transport aircraft than other concepts. Essentially, there are two technical challenges for vectored slipstream VSTOL. The first is achieving a high slipstream turning efficiency (defined by the thrust recovery factor F/T, which is the ratio of the resultant force divided by propeller thrust), in particular at the high turning angles required for VTOL flight. The second is providing adequate pitch control in hover and slow speed flight. Over forty years ago, the Breguet 941 STOL transport very successfully demonstrated that these challenges were manageable for STOL (but not VTOL). Small scale model research indicated that a slip-stream turning efficiency of F/T = 0.93 should be possible at higher Reynolds numbers for VTOL flight at a slipstream turning angle of 80 deg. The higher turning efficiency of F/T = 0.93 is made possible by the use of a canard surface mounted on each nacelle to help the wing flap system to efficiently vector the slipstream to angles greater than 90 deg. For the pitch control in hover and slow speed flight, five candidate solutions (trailing edge flaps, blade cyclic pitch, tail rotor, and modulation of slipstream or the engine exhaust) have been examinated using a 1/11-scale radio controlled vectored slipstream aircraft model. Based on this assessment, considering pitch control, weight, hover performance, cruise performance, and complexity, the trailing edge flaps are the best solution, but this is next to the poorest solution for providing the most pitch control.


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    Title :

    The vectored slipstream propfan - A promising approach for large VSTOL transports


    Additional title:

    Schubvektorsteuerung durch Umlenkung eines Propfan-Triebwerksstrahls - ein vielversprechender Ansatz für große Senkrechtstarter und Kurzstartflugzeuge


    Contributors:

    Published in:

    Publication date :

    2003


    Size :

    6 Seiten, 14 Bilder, 3 Tabellen, 2 Quellen



    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English





    THE VECTORED SLIPSTREAM PROPFAN HAS THE POTENTIAL FOR BEING THE BEST APPROACH FOR LARGE VSTOL TRANSPORTS

    Wernicke, K. G. / American Helicopter Society | British Library Conference Proceedings | 2001


    VSTOL Design Implications for Tactical Transports

    Brown, Derrell L. / Wollaston, James W. | SAE Technical Papers | 1987



    Propfan propulsion for commercial air transports

    Coussens, T.G. / Tullis, R.H. | Tema Archive | 1980