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XV-4 Hummingbird
First prototype XV-4 Hummingbird
Manufacturer Lockheed
First flight 7 July 1962
Status Both aircraft destroyed during testing
Primary user United States Army
Number built 2

The Lockheed XV-4 Hummingbird (originally designated VZ-10) was a U.S. Army project designed and built by the Lockheed Corporation in the 1960s, one of many attempts to produce a V/STOL vertical take off/landing jet. At a design speed of 336 mph (541 km/h), the Hummingbird was slower than some propeller-powered transports. Both prototype aircraft were destroyed in accidents.

Design and development[edit | edit source]

The design used doors at the top and bottom of the fuselage intended to augment thrust ejected into this area with cold air. In theory, a 11,607 lb (5,265 kg) aircraft could be lifted by a 6,600 lbf (29,000 N) engine. Unfortunately, performance was far below the estimates only 1.04 thrust-to-weight in practice and the prototype crashed on 10 June 1964, killing the pilot. The second aircraft was converted to lift jets instead, also crashing after several tests.

Rockwell's XFV-12 would be even less successful at venting cold air to augment thrust through the wings. The Lockheed F-35 Joint Strike Fighter would later employ a shaft-driven lift fan, also located in the fuselage.

None of the early American V/STOL designs would result in a production aircraft. The British Hawker Siddeley Harrier used vectoring nozzles, while the Russian Yakovlev Yak-38 Forger attack jet used lift jets in conjunction with rotating rear nozzles.

Testing[edit | edit source]

The first conventional takeoff flight of the first prototype, XV-4A (62–4503), took place on 7 July 1962. Initial tethered flight tests were carried out on 30 November 1962 with the first free hovering flight occurring on 24 May 1963. The first flight to transition from hovering to forward flight took place on 8 November 1963. 62–4503 was destroyed in a fatal crash in Cobb County on 10 June 1964.

Lockheed modified the second prototype aircraft between 1966 and 1968 to XV-4B standard. The two Pratt & Whitney JT12 engines were replaced with six General Electric J85 turbojets four of these units acting as lift jets. This aircraft crashed in Georgia on 14 March 1969, the pilot, Harlan J. Quamme, escaped uninjured by use of the ejection seat.

Specifications (XV-4A)[edit | edit source]

Data from Lockheed Aircraft since 1913[1]

General characteristics

  • Crew: 2
  • Length: 32 ft 8 in (9.96 m)
XV-4B 32.66 ft (10 m)
  • Wingspan: 25 ft 8 in (7.82 m)
XV-4B 25.66 ft (8 m)
  • Height: 11 ft 9 in (3.58 m)
XV-4B 12.25 ft (4 m)
  • Wing area: 104.00 sq ft (9.662 m2)
  • Empty weight: 4,995 lb (2,266 kg)
XV-4B 7,463 ft (2,275 m)
  • Gross weight: 7,200 lb (3,266 kg)
XV-4B 12,580 ft (3,834 m)


  • Maximum speed: 518 mph; 450 kn (833 km/h) at 10,000 ft (3,048 m)
XV-4B 463 mph (745 km/h)
  • Cruising speed: 390 mph; 339 kn (628 km/h)
  • Range: 600 mi; 521 nmi (965 km) normal
  • VTO range: 600 mi (966 km)
  • Rate of climb: 12,000 ft/min (61 m/s)
  • Wing loading: 69.2 lb/sq ft (338 kg/m2)
  • Thrust/weight: 1.176 lb/lbst (0.0115 kg/kN)
XV-4B 1.43 lb/lb (0.014 kg/kN)

See also[edit | edit source]

Notes[edit | edit source]

  1. Francillon, Rene J. (1988). Lockheed Aircraft since 1913 (Reprint ed.). London: Putnam & Company Ltd.. pp. 432–434. ISBN 0-87021-897-2. 

References[edit | edit source]

  • X-Planes and Prototypes by Jim Winchester

External links[edit | edit source]

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