This is the BELL Model D-2127 also known as the X-22A, a unique example. Bell initially developed an X-22 to meet a US Navy requirement for a VTOL research aircraft with tilting ducted fans, anticipating the AV-8A VTOL Harrier buys. The first and only X-22 (151520) flew from 17 March, 1966 until a hard landing on 8 August 1966 damaged it beyond repair. The second aircraft and only other one built was the X-22A 151521. That flew in January, 1967 and demonstrated full transitions to forward flight. It was tested for the tri-services; subsequently for the FAA and for NASA. Then, the Cornell Aeronautical Lab in New York flew it for 10 years on VTOL research until 1984, and retired it to the Niagara Aerospace Museum in New York. The 151521 number is the USN Bureau Number of the aircraft.
A variable stability system was incorporated from the beginning, allowing for simulation of operation of differing types of VTOL aircraft, (rather than just ones of its specific configuration) including that of the AV-8A/B Harriers, the first 50 of which were delivered to the US Marine Corps (a branch of the US Navy) starting in 1970. (Side tidbit: in September 1971 I visited the Hawker Works at Dunsfold and witnessed a special flight demonstration by test pilot Duncan Simpson of their company-owned AV-8A demonstrator with registration G-VTOL). Two crew were seated side-by-side in the X-22A. The tricycle landing gear (dual wheel nose, single wheel mains) were retractible. Unsolved continuing problems with the landing gear led to its being later locked down.
Not shown in the picture is the very tall vertical stabilizer. There was no rudder. Elevons mounted behind the four ducted fans were the only control surfaces. Tilting the ducts and altering the fans' (propellers) pitches comprised all the control movements. The top picture illustrates the ducted fans in the VTOL position used for takeoff, vertical climb and hover (only the forward two of the four large-diameter circular unfinished metal duct housings are fully visible). The four ducted fans can be rotated down to face forward for conventional forward flight. The rear two ducted fans are mounted outboard of the engines near the tips of the rear stub wing. The tips of the rear stub wing rotated with the ducts in line with the controlled duct thrust vector.
The X-22A aircraft was useful for VTOL research, simulating operations of theoretical aircraft. No production ensued. No aircrew were killed. The X-22 was a very cost effective, successful and valuable research program. I thank Micha Lueck for the his fine pictures of 151521 taken in the very confined, difficult area of the plane's exhibit.
Please click on the TOP picture to see the 151521 Aircraft Profile page with more of Micha's fine pictures 0f the X-22A.
Specifications and performance:
Power: 4 General Electric YT-58-GE-8D turboshaft
engines of 1,250 Hp each.
Engines are in the wing roots of the rear stub wing linked to a common driveshaft.
The four tilting ducted fans are connected to the
Max. speed: 509km/h (316 mph)
Max. altitude: 8,475m (27,800 ft.)
Max. weight: 8,172 kg (18,016 lbs.)
Span: 11.69m (39 ft. 3 in.)
Length: 12.06m (39 ft. 7 in.)
Height: 5.99m (19 ft, 8 in.)