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Bell X-22A

Bell Aerospace · Ducted-Fan VTOL Research · USA · Early Jet (1946–1969)

Bell X-22A — Ducted-Fan VTOL Research
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The Bell X-22A was a four-ducted-fan V/STOL prototype built for the U.S. Navy by Bell Aerospace in 1965-1966 to investigate vertical-takeoff troop-transport concepts. Two airframes were built; the first crashed on its second flight, and the second flew until 1984 as a NASA / U.S. Navy V/STOL handling-qualities research aircraft. The X-22A is one of the longest-running V/STOL programmes in U.S. history and the data it returned shaped both the cancelled Hiller-Boeing X-18 successor designs and, indirectly, the V-22 Osprey's tilt-rotor flight-control architecture.

The X-22A used four 7-ft-diameter ducted fans, each surrounded by a circular shroud, mounted at the corners of the fuselage on tilting nacelles. Four 1,250-shp General Electric T58 turboshafts (cross-shafted so that any engine could drive any rotor) provided the power. To take off vertically, all four ducted nacelles tilted to point straight up; for cruise, all four tilted forward 90° so the fans became conventional propellers. A side benefit of the ducted-fan arrangement was relatively low downwash velocity compared with a comparable open-rotor V/STOL — useful when operating from unprepared dirt strips or troop ships.

First flight came on 17 March 1966 with Bell test pilots Stan Kakol and Donald Adams. The first airframe was lost on 8 August 1966 when a hydraulic failure caused a hard landing; both pilots ejected via the early Bell Helmet Escape system and survived. The second X-22A continued flying through October 1984 — over 18 years of active research service. NASA used the aircraft as a generic V/STOL handling-qualities simulator with adjustable stability augmentation, generating the experimental flight-control data set that later informed both the V-22 and the Bell Eagle Eye unmanned tilt-rotor.

The X-22A never met its original 326 mph cruise-speed requirement (it managed about 256 mph) and the Navy did not pursue ducted-fan tilt-nacelle V/STOL further. The cancelled Hiller-Boeing X-18 tilt-wing predecessor had revealed wing-stall problems on transition that the X-22A's ducted-fan arrangement did not solve. The surviving X-22A is preserved at the Niagara Aerospace Museum in Niagara Falls, New York.

For Kids — a shorter, friendlier version

The Bell X-22A was an experimental American plane from the 1960s with four big ducted fans on its corners. Each fan could tilt up for hovering or forward for normal flight. The plane was built to test ideas for vertical-takeoff troop transports for the US Navy.

Two X-22As were built in 1965 and 1966. The first one crashed on its second flight, but the second X-22A flew safely for 18 years. NASA used it as a research plane until 1984.

The plane is about as long as a school bus. It had four General Electric T58 engines, each turning one of the four fans. The engines were cross-linked so one engine could spin any fan if another engine quit.

The X-22A was not built to enter service, but its data helped engineers design future tilt-rotor planes. The V-22 Osprey, today's most famous tilt-rotor, used many lessons learned from the X-22A program. The Bell X-22A was one of the longest-running vertical-takeoff research planes in American history.

Fun Facts

  • The X-22A had four big ducted fans at the corners of the body.
  • Each fan could tilt up for hovering or forward for normal flight.
  • Two X-22As were built — the first crashed on its second flight.
  • The second X-22A flew for 18 years as a NASA research plane.
  • All four fans could be powered by any of the four engines if one engine quit.
  • The X-22A helped engineers design the V-22 Osprey tilt-rotor.

Kids’ Questions

What is a ducted fan?

A ducted fan is a big propeller spinning inside a round shroud or 'duct.' The duct makes the fan more efficient and helps direct the air for thrust. Ducted fans are common on V/STOL planes because they can be safer than open propellers and make less noise. The X-22A had four ducted fans, each 7 feet across.

Why did the second X-22A fly for so long?

The data the X-22A returned was very valuable. Even though no troop transport was ever built from it, the X-22A taught engineers how tilting rotors and fans work in flight. NASA kept using it to study tilt-rotor handling until 1984, helping shape today's tilt-rotor planes like the V-22 Osprey.

Variants

X-22A #1 (s/n 151520)
First flight 17 March 1966. Lost on 8 August 1966 after a hydraulic failure caused a hard landing; both pilots ejected and survived.
X-22A #2 (s/n 151521)
Flew the bulk of the 18-year programme. Configured as a variable-stability research aircraft for NASA / U.S. Navy V/STOL flight-control studies. Preserved at the Niagara Aerospace Museum, NY.

Notable Operators

United States Navy
Sponsored the original 1962 V/STOL prototype contract and conducted early flight tests. Both airframes carried Navy bureau numbers.
NASA Langley Research Center
Operated the second airframe from 1971 to 1984 as a variable-stability V/STOL handling-qualities research platform. Generated flight-control data for tilt-rotor and lift-fan studies.

Frequently Asked Questions

How fast did the Bell X-22A fly?

Maximum demonstrated speed was about 256 mph (412 km/h) — short of the 326 mph (525 km/h) requirement set in the original 1962 Navy specification. The shortfall came from the ducted-fan installation's higher drag in cruise compared with open-rotor or tilt-rotor alternatives.

How is the X-22A different from the V-22 Osprey?

The V-22 Osprey uses two tilt-rotors with open prop-rotors at the wingtips. The X-22A used four ducted fans on tilting nacelles at the four corners of the fuselage. The X-22A's ducts cut downwash but added drag; the V-22's open rotors are more efficient in cruise. The Navy chose the V-22 architecture for the production tilt-rotor.

Who flew the Bell X-22A?

Bell test pilots Stan Kakol and Donald Adams made the first flight on 17 March 1966. NASA Langley's research-pilot pool flew most of the 1971-1984 envelope-expansion programme, including Lee Person and other V/STOL specialists.

Why did the X-22A programme last so long?

The second airframe was rebuilt as a variable-stability research aircraft — the pilot's controls fed through an analogue computer that could mimic any V/STOL airframe NASA wanted to study. This made it useful long after the original Navy operational requirement lapsed.

Where is the surviving X-22A today?

On display at the Niagara Aerospace Museum in Niagara Falls, New York — close to the Bell Aerospace plant where it was built (museum site).

Sources

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