One of the founders of Transcendental, Robert L. Lichten, left to take the lead on the design of the Bell XV-3, which began under a joint Army-Air Force program in 1951. The XV-3 used the reliable 450 hp Pratt & Whitney R-985 radial engine mated to a two-speed manual gearbox, similar in principal to that of the Transcendental 1G. The fuselage was 30 ft long and had a 31 ft wing span.
It made its first flight as a helicopter in August 1955, but crashed two months later before completing a full conversion. Extensive wind tunnel and rig tests were conducted after this, with pilots practicing the conversion process and gear changes (which required significant manipulation of the pitch and throttle controls and took about 20 seconds) in the tunnel. Rotor instability concerns led to a change from 23 ft three-bladed full-articulated rotors to 24 ft two-bladed semi-rigid rotors. The second XV-3 made its first flight on 12 December 1958, with a full conversion only 6 days later. Conversions over the full 90° could be conducted in 10 seconds. Inadequate power and high weight growth precluded the XV-3 from hovering out of ground effect. The XV-3 made 110 full conversions and over 250 flights before it was damaged in a wind tunnel test in 1965 when a rotor housing separated from the aircraft. The ejection seats were thankfully never needed: they ejected downward.
Source: AHS V/STOL Wheel
An excellent description of the design and development of the XV-3 Type can also be found in the reference below,
Source: "XV-3 Convertiplane - A Study in Innovation", Mark L. Isaac, Presented at the American Helicopter Society 64th Annual Forum, Montréal, Canada, April 29 – May 1, 2008
August 11, 1955
XV-3 (Ship 1): First flight of the Bell XV-3 tilt rotor (XV-3 Ship 1)
December 18, 1958
XV-3 (Ship 2): First 100% conversion from rotor-borne to wing-borne flight by a tilting rotor aircraft (Bell XV-3 Ship 2)