The Osprey's Antecedents
 
 
Besides the helicopter, only two lines of development have been
successful in man's quest for vertical flight.  The most
productive so far has been the vectored thrust type, as
exemplified by the McDonnell Douglas AV-8B Harrier.  The second
-- with the longest period of development in aviation history --
is the tilt-rotor type, of which the Bell XV-22 is the latest and
best offering. 
 
In 1951, Bell Aircraft began a long and ardent affair with the
tilt-rotor aircraft.  The first prototype of this type of
aircraft -- the XV-3 -- was, like every helicopter of the period,
underpowered.  Nonetheless, in a fifteen-year test program, this
prototype made over 250 flights, including 110 conversions from
vertical to horizontal flight.  The success of these tests has
sustained Bell's basic faith in the concept. 
 
After the XV-3, Bell followed with the XV-15 which was powered by
two Lycoming jet engines.  By 1980, this aircraft had set a
series of records, including an unofficial speed record of 346
mph, sensational for vertical takeoff and landing (VTOL)
aircraft.  From the  XV-15 program, Bell gathered experience and
enthusiasm for the creation of the XV-22, the Osprey.