Lockheed 330 Hummingbird / VZ-10 / XV-4
A contract for two prototypes of a new-type VTOL aircraft was placed with the Lockheed company's Georgia factory by the U.S. Army in June 1961. This followed more than two years of privately-financed development of the jet ejector augmentation principle by Lockheed, including wind tunnel and test rig work.
The Army contract was for the Lockheed Model 330 Humming Bird, a research vehicle which was to be capable of development for use in the battlefield surveillance and Army support role.
Basis of the Lockheed concept is to augment the thrust of a jet engine by ducting its exhaust through a large-diameter tube so that a large volume of cold air is drawn through it by friction and vacuum effect. This can augment the basic thrust of the engine by as much as 40 per cent.
In the VZ-10 - which was re-designated XV4A in July 1962 - two 3,000 lb.s.t. Pratt & Whitney JT12A-3s are located each side of the fuselage above the wing root. For vertical operations, their exhaust jet is turned through 180 degrees and ejected downwards through a series of nozzles into a duct or mixing area in the centre fuselage. Doors covering this duct, top and bottom, are opened. To convert from vertical to horizontal flight, the VZ-10 is first tilted slightly nose-down to obtain a small thrust component from the jet exhaust from the fuselage duct. As speed builds up the wings begin to contribute lift and the thrust of one engine is then deflected from vertical to horizontal. This increases the speed still more and the second engine can then be deflected, too, and the duct doors are closed.
The first VZ-10 (62-4503) made its first flight at Marietta on July 7th, 1962, taking off conventionally. Hovering trials began in 1963. On 20 November 1963 the first successful flight involving transitions from vertical to horizontal flight, and vice versa, was completed.
The second VZ-10 was tested in the 40 ft by 80 ft low-speed tunnel at Ames Research Center before joining the flight test programme.
By then, redesignated XV-4A, the two prototypes were handed over to the US Army. In late 1966 Lockheed modified one of the XV-4As to a new XV-4B configuration, the major change being replacement of the XV-4A's two 1361kg thrust engines by four each of 1368kg thrust. Testing began in August 1968, but when the aircraft was destroyed in an accident in early 1969 further development was abandoned.
Max take-off weight: 5706 kg / 12580 lb
Wingspan: 8.25 m / 27 ft 1 in
Max. speed: 745 km/h / 463 mph