Lockheed XV-4 Hummingbird

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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 to demonstrate the feasibility of using VTOL for a surveillance aircraft carrying target-acquisition and sensory equipment.[1] It was designed and built by the Lockheed Corporation in the 1960s, one of many attempts to produce a V/STOL vertical take off/landing jet. Both prototype aircraft were destroyed in accidents.

Design and development

Vertical take-off lift was obtained by exhausting the engine flow downward through multiple nozzles. The nozzle thrust was augmented by a secondary flow of cold air.[1] 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 producing lift by using engine exhaust to entrain cold air, in this case through flaps on the wings. The Lockheed F-35 Joint Strike Fighter would later employ a shaft-driven lift fan 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.


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)

Data from Lockheed Aircraft since 1913[2]

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

Aircraft of comparable role, configuration and era
Related lists


  1. 1.0 1.1 "Hummingbird A Promising Augmented-Jet VTOL Aircraft" Flight International, 3 April 1962
  2. Francillon, Rene J. (1988). Lockheed Aircraft since 1913 (Reprint ed.). London: Putnam & Company Ltd. pp. 432–434. ISBN 0-87021-897-2.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. "The Engines of Pratt & Whitney:A Technical History" Jack Connors,published by AIAA, ISBN 978-1-60086-711-8, p.287


  • X-Planes and Prototypes by Jim Winchester

External links