Lockheed XV-4 Hummingbird

https://en.wikipedia.org/wiki/Lockheed_XV-4_Hummingbird

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. 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.

Vertical take-off lift was obtained by exhausting the engine flow downward
through multiple nozzles, augmented by a secondary flow of cold air. But the
performance was far below estimates with only a 1.04 thrust-to-weight ratio, and
the prototype crashed on 10 June 1964, killing the pilot. The second aircraft
was converted to lift jets instead, yet also crashed 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.


Role
VTOL

Manufacturer
Lockheed

First flight
7 July 1962

Status
Both aircraft destroyed during testing

Primary user
United States Army

Number built
2

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; pilot Harlan J. Quamme escaped uninjured,
using the ejection seat.

Specifications (XV-4A)

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)Powerplant: 2 × Pratt & Whitney JT12A-3LH turbojet,
3,300 lbf (15 kN) thrust each take-off thrust
Powerplant: 6 × General Electric J85-GE-19 turbojets, 3,015 lbf (13.41 kN)
thrust each XV-4B only, 4 for lift,2 for horizontal flight

Performance
Maximum speed: 518 mph; 450 kn (833 km/h) at 10,000 ft (3,048 m)

XV-4B 463 mph (745 km/h)Cruise 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)



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