https://en.wikipedia.org/wiki/Bell_X-22
The Bell X-22 was an American V/STOL X-plane with four tilting ducted fans.
Takeoff was to selectively occur either with the propellers tilted vertically
upwards, or on a short runway with the nacelles tilted forward at approximately
application of vertical takeoff troop transporters such as the preceding Hiller
X-18 and the X-22 successor, the Bell XV-15. Another program requirement was a
true airspeed in level flight of at least 525 km/h (326 mph; 283 knots).
In 1962, the United States Navy announced their request for two prototype
aircraft with V/STOL capability, powered by four ducted fan nacelles. Bell
Helicopter already had extensive experience with VTOL aircraft and was able to
utilize an already developed test mockup. In 1964 the prototype, internally
referred to by Bell as Model D2127, was ordered by the Navy and received the
X-22 designation. It was unveiled at an event in Niagara Falls in May 1965.
Three-bladed propellers were mounted on four wings and, synchronized through a
wave-interconnection system, were connected to four gas turbines which, in turn,
were mounted in pairs on the rear wings. Maneuvering was achieved by tilting the
propeller blades in combination with control surfaces (elevators and ailerons),
which were located in the thrust stream of the propellers.
Role
V/STOL prototype
Manufacturer
Bell Aircraft
First flight
17 March 1966
Status
One preserved, one scrapped
Primary user
Bell
Number built
2
The maiden flight of the prototype occurred on 17 March 1966. In contrast to
other tilt-rotor craft (such as the Bell XV-3), transitions between hovering and
horizontal flight succeeded nearly immediately. However, interest increased more
towards VTOL and V/STOL properties, not the specific design of the prototype.
Due to failure of a propeller control, described by the test pilot, Stanley
Kakol, as the only non-redundant component in the power chain, the prototype
crashed on 8 August 1966 and technicians stripped it for components in order to
make the second prototype flight capable. The fuselage was still used as a
simulator for some time afterwards.
The second X-22 first flew on 26 August 1967. Early that year, it was equipped
with a variable flight control and stabilizer system from Cornell Aeronautical
Laboratory, which improved flight performance. Although the X-22 was considered
to be the best aircraft of its type at the time, the program was canceled. The
required maximum speed of 525 km/h was never reached. The second prototype was
moved to Cornell Aeronautical Laboratory for further testing; the last flight
occurred in 1988. Although the ducted fan propellers were considered usable,
they were not used again on a US military aircraft until the F-35B.
Specifications (X-22A)
General characteristics
Crew: two + six passengers
Length: 39 ft 7 in (12.07 m)
Wingspan: 39 ft 3 in (11.96 m)
Wingspan (front wing): 22.916 ft (6.98 m)
Height: 20 ft 8 in (6.31 m)
Empty weight: 10,478 lb (4,753 kg)
Max takeoff weight: 17,644 lb (8,003 kg)
kW) each
Propellers: three-bladed propellers mounted in wingtip swivelling ducts, 7 ft 0
in (2.13 m) diameter
Performance
Maximum speed: 221 kn (254 mph; 409 km/h)
Range: 387 nmi; 716 km (445 mi)
Service ceiling: 27,800 ft (8,500 m)
Hover ceiling in ground effect : 12,000 ft (3,658 m)
Hover ceiling out of ground effect : 6,000 ft (1,829 m)
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