Bell X-22

Bell X-22
Type:	V / STOL - experimental aircraft
Design country:	United States
Manufacturer:	Bell Aircraft Corporation
First flight:	March 17, 1966
Commissioning:	Flight tests ended in 1988
Production time:	Was never mass-produced
Number of pieces:	2

The Bell X-22 was a V / STOL - experimental aircraft with four tilting coat propellers . The take-off should be able to take place either vertically, with the propellers tilted upwards by 90 °, or on a short runway with the propellers tilted forward by about 45 ° (V / STOL = Vertical / Short Take-Off and Landing, vertical / short take-off and landing ). At the same time, the X-22 should provide more information about the tactical usability of a vertical take-off vehicle as a troop transport, like the Hiller X-18 before it and the Bell XV-15 after it . Another requirement was to achieve a speed of at least 525 km / h in level flight.

history

In the early 1960s, both the US Air Force , the US Army and the US Navy wanted to test the concept of the ducted propeller for a VTOL aircraft. In the corresponding tender, Bell prevailed against a draft by Douglas.

On November 30, 1962, the US Navy announced the construction of two prototypes with V / STOL properties and four ducted propellers. At Bell we had start- already in the 1950s intensively with vertical and concerned country capable aircraft and could on existing experience with the Bell XV-3 and the model 65 and a test dummy fall back from the structural design of the model D2127 adopted has been. However, the prototypes received serial numbers (151520 and 151521) of the US Navy and were given the military type designation X-22.

In 1963, models of various scales were tested in NASA wind tunnels. In 1964, tests of the drive and control systems began on test stands and at the end of 1964 the assembly of the first machine began at the factory in Wheatfield near Buffalo, the two prototypes being the last machines built there. The first machine was rolled out on May 25, 1965 and the second on October 30, 1965. On March 17, 1966, the ten-minute first flight of the first prototype with Stanley Kakol and Paul Miller took place in Wheatfield after numerous static tests. In contrast to other tilt rotor aircraft (e.g. the Bell XV-3 ), numerous transitions occur almost immediately (transition from hovering to level flight and vice versa). The focus was more on researching the VTOL and V / STOL properties than this special design.

The first prototype crashed on August 8, 1966 due to negligent maintenance, which led to the failure of the hydraulic system. The technicians cannibalized it to make the not yet completed second prototype airworthy; the fuselage was still used as a simulator at Calspan for some time.

The second X-22 first flew on January 26, 1967, and in March 1967 the first transition from vertical to cruise took place. From January 1968 the machine was tested by the three branches of the armed forces and officially handed over to the US Navy on May 19, 1968. On July 30, 1968, a hovering flight was achieved 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 Resolving Airspeed System) from the Cornell Aeronautical Laboratory , which expanded the flight performance range. A total of 272 flights with 280 flight hours, 130 VTOL take-offs and 236 VTOL landings were carried out during the subsequent tests in Buffalo (New York). Although the X-22 was considered the best aircraft of its kind to date, the program was discontinued. The required top 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, with more than 400 flight hours resulting from over 500 flights. It is currently on display at the Niagara Aerospace Museum , New York .

Although the ducted propellers were thought to be useful, they have not since been used on a US military aircraft.

construction

The two-seat machine had a box-shaped fuselage with a vertical tail unit without an elevator. The retractable landing gear consisted of two main landing gears with single tires and a nose wheel with double tires. The four jacketed trifoliate Hamilton Standard propellers were mounted in nacelles at the wings and have a composite undulatory and transmission system of four shaft turbines YT58-GE-driven 8D, which were mounted in pairs on the rear stub wings. The gondolas could be swiveled hydraulically by up to 95 °. The aircraft was controlled by adjusting the blades of the propellers in combination with the combined elevator and ailerons (elevons) attached to the wake of the propellers and the pivoting of the nacelles. In the cockpit, which was equipped with zero-zero ejection seats, there were conventional control elements with sticks and rudder pedals, which were supplemented by a blade adjustment lever and switch for the nacelle adjustment. An electro-hydraulic trim system generated realistic control pressures in all flight areas. The VSS variable control system developed by Cornell Aeronautical Laboratory made it possible to simulate other VTOL aircraft, whereby for safety reasons only the inputs from the pilot's left seat were influenced.

Technical specifications

Parameter	Data
Construction year	1966
Manufacturer	Bell helicopter
span	11.96 m (rear wings) 7.01 m (front wings)
length	12.07 m
height	6.31 m
Propeller diameter	2.13 m
Preparation mass	4763 kg
Empty mass	6622 kg
Takeoff mass	8020 kg
crew	2
Top speed	410 km / h
Max. Altitude	8475 m
Hovering altitude with ground effect	3660 m
Hovering altitude without ground effect	1830 m
Range	890 km
Engines	4 General Electric -YT58-GE-8D- shaft turbines with 932 kW (1267 PS ) each

See also

• Bell Boeing V-22
• List of aircraft types
• List of test aircraft

Web links

Commons : Bell X-22  - collection of pictures, videos and audio files

Individual evidence

1. ↑ Description on history.nasa.gov p. 29. (PDF; 1.2 MB) Retrieved on February 11, 2013 . 
2. ↑ ^{a b} FlugRevue November 2011, pp. 92–95, Flying Simulator - Bell X-22A.