Bell XV - 3 The Bell XV - 3 ( " Bell 200 " ) was a tiltrotor aircraft developed by Bell Helicopter for a joint research program between the United States Air Force and the United States Army in order to explore convertiplane technologies . The XV - 3 featured an engine mounted in the fuselage with drive shafts transferring power to two - bladed rotor assemblies mounted on the wingtips . The wingtip rotor assemblies were mounted to tilt 90 degrees from vertical to horizontal , which was designed to allow the XV - 3 to take off and land like a helicopter but fly at faster airspeeds , similar to a conventional fixed - wing aircraft . The XV - 3 was first flown on 11 August 1955 . Although it was limited in performance , the aircraft successfully demonstrated the tiltrotor concept , accomplishing 110 transitions from helicopter to airplane mode between December 1958 and July 1962 . The XV - 3 program ended when the remaining aircraft was severely damaged in a wind tunnel accident on 20 May 1966 . The data and experience from the XV - 3 program were key elements used to successfully develop the Bell XV - 15 , which later paved the way for the V - 22 Osprey . Design and development . In 1951 , the Army and Air Force announced the Convertible Aircraft Program and released the Request for Proposals ( RFP ) to solicit designs from the aircraft industry . In October 1953 , Bell Helicopter was awarded a development contract to produce two aircraft for testing purposes . The original military designation was " XH - 33 " , classifying it as a helicopter , but its designation was changed to " XV - 3 " in the convertiplane series . The designation was changed once again in 1962 to " XV - 3A " when the V - prefix was changed to mean VTOL . The leading designers were Bob Lichten and Kenneth Wernicke . The first XV - 3 ( s / n 54 - 147 ) flew on 11 August 1955 with Bell Chief Test Pilot Floyd Carlson at the controls . On 18 August 1955 , the aircraft experienced a hard landing when the rotor developed a dynamic instability . Bell attempted to remedy the situation , and flight testing resumed on 29 March 1956 after additional ground runs . Bell continued to expand the flight envelope of the XV - 3 , but on 25 July 1956 , the same rotor instability occurred again . Flight testing of the XV - 3 resumed in late September 1956 . Then , on 25 October 1956 , the aircraft crashed when the test pilot blacked out due to extremely high cockpit vibrations . The vibrations resulted when the rotor shafts were moved 17 degrees forward from vertical . The test pilot , Dick Stansbury , was seriously injured , and the aircraft was damaged beyond repair . Bell modified the second XV - 3 ( s / n 54 - 148 ) by replacing the three - bladed rotors with two - bladed rotors , and after taking extensive precautions , the second XV - 3 began testing at the National Advisory Committee for Aeronautics ' ( NACA ) Ames Aeronautical Laboratory wind tunnel facility on 18 July 1957 . Flight testing for ship # 2 began on 21 January 1958 at Bell ' s facility . By April , the aircraft had expanded the flight envelope to 127 mph ( 205 km / h ) as well as demonstrating full autorotation landings and 30 - degrees forward transitions with the rotor pylons . On 6 May 1958 , another instance of rotor instability occurred when the pylons were advanced to 40 - degrees forward pylon angle , and the XV - 3 was grounded once more . The XV - 3 returned to the Ames wind tunnel in October 1958 to collect more data before it could be flown again . As a result of the wind tunnel testing , the rotor diameter was reduced , wing structure was increased and strengthened , and the rotor controls were stiffened . The XV - 3 resumed flight testing at Bell ' s facility on 12 December 1958 . On 18 December 1958 , Bell test pilot Bill Quinlan accomplished the first dynamically stable full conversion to airplane mode , and on 6 January 1959 , Air Force Captain Robert Ferry became the first military pilot to complete a tiltrotor conversion to airplane mode . Flight testing at the Bell facilities was completed on 24 April 1959 , and the aircraft was shipped to Edwards Air Force Base . The military flight testing of the XV - 3 began on 14 May 1959 . Promoted to the rank of Major , Robert Ferry would coauthor the report on the military flight evaluations , conducted from May to July 1959 , noting that despite the deficiencies of the design , the " fixed - wing tilt - prop , " or tiltrotor , was a practical application for rotorcraft . Following the completion of the joint service testing , the aircraft was returned to the Ames facility , where on 12 August 1959 , Fred Drinkwater became the first NASA test pilot to complete the full conversion of a tiltrotor to airplane mode . On 8 August 1961 , Army Major E . E . Kluever became the first Army pilot to fly a tiltrotor aircraft . Testing would continue through July 1962 as NASA and Bell completed wind tunnel testing to study pitch - flap coupling exhibited by the tiltrotor in an effort to predict and eliminate the aeroelastic dynamic rotor instability ( referred to simply as " pylon whirl " ) that had caused problems throughout the program . In April 1966 , Bell Helicopter aerodynamicist Dr . Earl Hall published an analysis of the XV - 3 program data explaining the tiltrotor aircraft pylon whirl instability . In order to establish Hall ' s findings and develop a computer model , NASA agreed to conduct wind tunnel testing at the Ames 40 x 80 wind tunnel . As the engineers were completing the last planned test , a wing tip failure caused both rotors to fail , resulting in severe damage of the XV - 3 and damage to the wind tunnel . On 14 June 1966 , NASA Ames Research Center announced the completion of XV - 3 testing . The XV - 3 had accomplished a total of 250 flights , accumulated 125 flight hours , and completed 110 full conversions . Survivors . In late 1966 , the sole remaining XV - 3 , serial number 54 - 148 , was moved to outside storage at Davis - Monthan AFB in Tucson , Arizona . In 1984 , the Bell XV - 15 flight test team discovered the aircraft stored outside the Army ' s Aviation Museum during the XV - 15 visit to Fort Rucker , Alabama , as part of a demonstration tour . 54 - 148 was repaired by December 1986 , with Army support and the leadership of former Bell XV - 3 engineer Claude Leibensberger , but the aircraft was disassembled and placed into indoor storage . On 22 January 2004 , the XV - 3 was delivered to Bell Plant 6 in Arlington , Texas . In 2005 , Bell Helicopter employees began work to restore 54 - 148 to museum display condition , this time led by former XV - 3 engineer Charles Davis . Following a two year restoration , the XV - 3 was transferred to the National Museum of the United States Air Force in Dayton , Ohio . It was placed on display in the Museum ' s Post - Cold War Gallery in June 2007 , and as of 2011 is on display in the Research & Development Gallery .