The Hiller X-18 was a tilt wing aircraft change to test the Kippflügelbauweise as well as the detection of the advantages and disadvantages of a V / STOL aircraft.
It was the first heavy transport aircraft of this design with at least theoretical VTOL ( vertical take-off and landing ) properties; since the proposed test series but only surface tilts up to max. ROCHE 50 °, the X-18 are only detectable STOL (Start over short distances ) capabilities as well as some pure hovers in practice. A transition (transition from hover to horizontal flight ) is not documented.
In February 1957, the Hiller Aircraft Corporation of the United States Air Force awarded the contract to build ten test aircraft in Kippflügelbauweise. The engineers drew on existing components: the fuselage of the Chase YC -122 served as a base, the drive components were no longer needed parts from the set "Heck starter " program of the United States Navy. Thus came the counter ( coaxial ) three-blade propeller of the experimental aircraft Lockheed XFV -1 and Convair XFY -1 " Pogo ", which were originally also in the XFV -1 are used in the Allison turbine X-18 used. For the pitch control was provided by a Westinghouse J34 jet engine that produced a variable shear beam with an extended outlet nozzle in the rear fuselage section.
This " modular system " of the first flight of the X-18 was already on November 20, 1959 instead, but a pure horizontal flight as wing aircraft. Exactly 20 test flights were carried out; a mechanical breakdown during the twentieth flight in July 1961 provided together with the disappointing test results for the immediate cessation of the X-18 program. Little is known about the whereabouts of the only copy; probably it was scrapped at the Edwards Air Force Base. The other nine planned machines were never built.
However, it had won by the X-18 some input to the development directly into a promising concept, namely the Ling- Temco - Vought XC- 142.