The Bell X -22 was a V / STOL experimental aircraft with four propellers tiltable coat. The start should either vertically, can be made with 90 ° tilted upwards propellers, or on a short runway at about 45 ° tilted forward propellers (V / STOL = Vertical / Short Take- Off and Landing, vertical take off and land / short ). At the same time the X-22 should bring more information about the tactical usefulness of a VTOL aircraft as a troop transport, as it was before her the Hiller X-18 and according to her the Bell XV- 15th Another requirement was to achieve a speed of at least 525 km / h in horizontal flight.
Beginning of the 1960s wanted both Air Force, Army and Navy to test the concept of the jacket propeller for a VTOL aircraft. In the corresponding tender, Bell stood out against a draft of Douglas.
On November 30, 1962, the U.S. armed forces gave orders to build two prototypes with V / STOL capabilities and four coat propellers. At Bell had already dealt in the 1950s intensively with vertical takeoff and landing capable aircraft and was able to draw on existing experience with the Bell XV- 3 and the Model 65 and a test dummy, taken over the structural design of the model D2127 of which was. The prototypes were however serial numbers ( 151 520 151 521 and ) the U.S. Navy and received the military type designation X- 22nd
1963 were tested at different scales in wind tunnels of NASA models. 1964 began testing the drive and control systems on test stands and the end of 1964 the installation of the first machine began at the plant in Wheatfield at Buffalo, the two prototypes were the last locally built machines. On May 25, 1965, the rollout of the first machine and on 30 October 1965, the second took place. On March 17, 1966, the ten-minute maiden flight of the first prototype with Stanley Kakol and Paul Miller took place in Wheatfield after numerous static tests. Unlike other Kipprotorflugzeugen (eg, the Bell XV -3) reach virtually straight away numerous transitions ( transition from hover to level flight and vice versa). The interest was more research into the VTOL and V / STOL characteristics as less this special design.
Due to negligent maintenance, which led to the failure of the hydraulic system, the first prototype crashed on August 8, 1966. The technician killed him to make the unfinished second prototype capable of flight, the fuselage was still used for some time as a simulator at Calspan.
The second X-22 first flew on 26 January 1967, and in March 1967, the first transition from vertical to cruise. As of January 1968, the machine from all three branches of the armed forces has been tested and officially handed over on May 19, 1968 to the U.S. Navy. It succeeded on 30 July 1968, hovering at an altitude of 2445 m. In the spring of 1970, she was equipped with the variable flight control and stabilization system LORAS (Linear Omnidirectional Airspeed Resolving System) of the Cornell Aeronautical Laboratory, which the flight power range extended. Overall, the following tests were performed in Buffalo (New York) still 272 flights with 280 flight hours, 130 VTOL take-offs and 236 VTOL landings. Although the X - 22 as the aircraft was hitherto best of its kind, the program was discontinued. The required maximum speed of 525 km / h was never reached. The second prototype went to Cornell Aeronautical Laboratory for further testing, which lasted until October 1984. The last documented flight took place in 1988, where among the over 500 flights more than 400 flight hours came about. He is currently on display at the Niagara Aerospace Museum, New York.
Although the ducted propeller were considered useful, they were never used again in a U.S. military aircraft.
The two-seater machine had a box-shaped hull with a rudder without elevator. The retractable landing gear consisted of two single -tyred main landing gear and a double ringed nose wheel. The four jacketed trifoliate Hamilton Standard propellers were mounted in nacelles on the wings and were driven by a composite shaft and gearbox system of four shaft turbines YT58 -GE- 8D, which were mounted in pairs on the rear stub wings. The gondolas could be hydraulically pivot up to 95 °. Controlled the aircraft was by the pitch of the propeller in combination with the fixed in the wake of the propeller combined elevator and ailerons ( elevons ) and the pivoting of the gondolas. In equipped with Zero -Zero ejection seats were cockpit with joystick and rudder pedals conventional control devices available, which were complemented by a collective stick and switches for the cable adjustment. An electro -hydraulic trim system produced realistic control pressures in all flight regimes. Developed by the Cornell Aeronautical Labatory variable control system VSS enabled the simulation of other whiz, where for security reasons only the entries of the left pilot seat were affected.