Lockheed XV-4 Hummingbird
The Lockheed XV -4 Hummingbird ( Hummingbird ) ( original designation VZ- 10 after the designation system for aircraft in the U.S. Army from 1956 to 1962 ) was a constructed and tested in the sixties VTOL experimental aircraft.
History
Once the principle of vertical takeoffs with a vertical plane ( tail sitter ) in the form of the Ryan X -13 Vertijet was abandoned, new technologies had to be considered. They tried a technique to develop horizontally aligned whiz (flat riser ) to equip with more thrust than the engines produce only nominally (jet augmentation ). Two companies, Lockheed - Georgia and General Electric (in collaboration with Ryan ) have been instructed to develop aircraft that were to test the new radical ideas in the experimental situation.
"Jet augmentation "
The principle of jet augmentation to translate into German with about jet or thrust augmentation was first described by Theodore von Kármán 1949. It is a remarkably simple theory that connects the law of conservation of momentum to the flow Bernoulli's law. The exhaust of the jet engine passes into a large chamber before it leaves on the other side through an opening again. When the hot and quick exhaust air exits the chamber draws air from the environment as compensation in the chamber. The kinetic energy of the air taken in leads to an additional thrust.
Construction
To test the principle in practice, Lockheed built in early 1959 a flying test frame ( test rig ). First driven by two Fairchild J44 engines succeeded with a nominal engine thrust of 2,000 lb, a weight of 2600 lb to lift vertically, which corresponds to an augmentation of about 30 %. With stronger Continental J69 engines later was even an augmentation of 45%. It then various Konzepstudien for a used aircraft under the collective name of GL -224 and GL -228 were created.
In August 1959, Lockheed presented the final design with the designation Model 330 Hummingbird U.S. Army Transportation Research Command as an integrated VTOL aircraft for battlefield surveillance and target acquisition ago. The mission of the U.S. Army in July 1961 included then only the construction of two test aircraft, since the proposed technique has been regarded as not yet been sufficiently tested. The aircraft received the U.S. Army designation VZ -10 ( s / n 62-4503 and 62-4504 ).
Two Pratt & Whitney PW -3 JT12A ensured for both the lift and propulsive thrust. The dimensions of the hull and its chunky appearance was mainly by the size of the required mixing chamber. The mixing chamber is located in the fuselage between the engines and is covered by flaps on the top and bottom of the fuselage in level flight. For the control, there are nozzles on all outer points of the aircraft. At the front and the exhaust Heckdüse beam is tapped as is used for the two nozzles at the wing tips of compressed air from the compressors.
Testing
The first conventional flight of the first prototype ( XV -4A, 62-4503 ) took place on July 7, 1962. The first tethered float was carried out on 30 November 1962 the first free float on 24 May 1963. The first flight with the transition from hover to forward flight and aerodynamically assisted back to float succeeded on 8 November 1963.
This prototype crashed on 10 June in 1964 in Cobb County, where the pilot was killed.
Lockheed modified in late 1966 or 1968, the second XV- XV- 4A to 4B ( 62-4504 ). The two engines ( Pratt & Whitney JT12A -PW -3), each with 1361 kg thrust by six engines (General Electric J85 -GE -19) replaced with each 1368 kg thrust. Four engines were working there as pure and lift engines were installed in the fuselage center as a replacement of the mixing chamber. The second aircraft with the pilot Harlan J. Quamme at the wheel crashed in Georgia on 14 March 1969. The pilot survived unharmed thanks to his ejection seat.