XV-15 litho - NASA's History Office

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Appendix C—Chronology
1452-1519 Leonardo da Vinci credited with the design of the first helicopter,
basically a helical airscrew.
1924 Henry Berliner flies fixed-wing biplane with large diameter
fixed-pitch propeller mounted on a tiltable vertical
shaft near the tip of each wing.
September 1930 “Flying Machine” patent, issued to George Lehberger,
employs use of a relatively low disc loading thruster (propeller)
that can tilt its axis from the vertical (for vertical
lift) to the horizontal (for propulsive thrust).
Late 1930s Baynes Heliplane patent issued in England.
1937 Focke-Wulf Fw-61 (Germany) lateral-twin rotor helicopter
flown.
1942 Focke-Achgelis FA-269 trail-rotor convertiplane project
initiated.
Early 1940s Platt-LePage Aircraft Company conduct preliminary
design work on tilt rotor aircraft.
January 1947 Mario Guerrieri and Robert Lichten establish
Transcendental Aircraft Company to develop convertiplane
(tilt rotor aircraft).
August 1950 U. S. Army and U. S. Air Force announce competition to
design a Convertiplane. Bell Helicopter and
Transcendental Aircraft submit bids.
May 1951 USAF Air Research and Development Command awards
contract to Bell to build mockup and begin detailed design
of a flight tilt rotor aircraft.
October 1953 Award of U.S. Air Force contract for development, prototype
construction, and testing of two XH-33 (later designated
XV-3) full-scale “tilting-thrust-vector convertiplanes”
to Bell Helicopter Company.
15 June 1954 First flight of Transcendental Aircraft Corporation
Model 1-G tilt rotor aircraft.
15 February 1955 Platt patent of tilt rotor aircraft, No. 2,702,168 granted.
February 1955 First XV-3 rolled out.