McDonnell
XL-25/XH-35/XV-1 Convertaplane
First helicopter to exceed 200 miles/hour in level flight
First
tethered hover flight: February 11, 1954
First
free hover flight: July 14, 1954
First
transition: April 29, 1955
The McDonnell XV-1 resulted from an early 1950 Army/Air Force design competition for a relatively high-speed VTOL aircraft. The initial application was for Army liaison missions: it was expected that its development would also provide the basis for design of a larger aircraft. The same reciprocating engine was used to turn the rotor for hover and the propeller for high-speed forward flight, the former by supplying compressed air to tip-jet units and the latter by direct drive. Fuel was burned in the tip-jets with a resulting loud noise and visual flash, considered unfavorable traits by the military.
Although a product did not result from the XV-1 program, it provided insight at speeds from hover up to 200 mph into the design requirements for an unloaded-rotor VTOL aircraft.
By Tommy Thomason
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