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The Focke-Wulf Triebflügel (wing-driven) fighter was a German tail-sitter project during the Second World War. Three wings were mounted radially as a rotor on a rotating section of the fuselage and driven by small jet engines on the wingtips. The aircraft was supposed to be propelled by this wing rotation. In fact, it was more akin to a helicopter, generating lift by rotating winglets or blades, than to an airplane, which generates lift from the forward speed pushing air over the wings of the plane. It would not make conventional landings, and the entire body of the aircraft shifted from a vertical to a horizontal orientation and back again for standard flight.
The Heinkel Lerche project and the later French postwar SNECMA Coléoptère had a circular wing which formed a duct around the proprotor. The French aircraft flew but never achieved the transition between vertical and horizontal flight.
After the war, the USA experimented with propeller-driven design configurations fitted with either delta wings for forward flight, as with the Convair XFY Pogo which successfully demonstrated the full transition between flight modes, or with conventional wings as with the Lockheed XFV Salmon, which used an X-configuration cruciform tail instead to rest upon, and which never managed a transition from vertical to horizontal flight involving vertical landings.
A later jet-powered design, the Ryan X-13 Vertijet, first flew in 1955. Two prototypes were made, both flew, made successful transitions to and from horizontal flight, and landed. The final test flight was near Washington DC in 1957.
An inherent problem with these tail-sitter designs was the lack of ability to transition the pilot to a comfortable position from which to control his descent. This led to the concept being abandoned for a time once a more practical form of VTOL appeared, in the form of the thrust vectoring Hawker P1127 in the 1960s.
Studies and wind tunnel models were made of a tail-sitting version of the F-16 that would be ship based. It had a hinged nose section.
An unmanned UAV does not suffer the problem of pilot attitude. The Dornier Aerodyne is of ducted-fan configuration similar to a coleopter, and a test UAV flew successfully in hover mode in 1972, before development was discontinued.
List of tail-sitters
|Convair XFY-1 Pogo||USA||1954||Fighter||Prototype|
|Focke-Wulf Triebflügel||Germany||1944||Interceptor||Project||Rotor wing around middle of fuselage. In-flight transition never resolved.|
|Rotary Rocket Roton ATV||USA||1999||Experimental||Prototype||Rotorcraft test vehicle for proposed SSO space launcher.|
|Ryan X-13 Vertijet||USA||1955||Experimental||Prototype|
|SNECMA Coléoptère||France||1959||Experimental||Prototype||Never achieved transition.|
- Darling, Jeff (2011-06-13). "Ryan X-13 Vertijet". Diseno. Retrieved 2014-02-09.
- Choi, Charles Q. (2010-01-19). "Electric Icarus: NASA Designs a One-Man Stealth Plane". Scientific American. Retrieved 2010-02-27.
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