General Electric J79
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The General Electric J79 is an axial-flow turbojet engine built for use in a variety of fighter aircraft and bomber aircraft. Produced by General Electric Aircraft Engines, it was one of the first US-designed engines to outperform designs from the United Kingdom , which had previously led in the jet field.
It was developed in the 1950s as an outgrowth of the General Electric J73 engine program, originally called J73-GE-X24A, intended for reliable Mach 2 performance. J79 was a single-shaft turbojet with a 17-stage compressor with a novel arrangement of variable stator blades which allow the engine to develop pressure similar to a two-stage engine at a much lower weight. Each blade is made largely of titanium which was not used for large aircraft structures until the 1960s, and each blade today costs several thousand dollars to replace.
The first flight of the engine was in 1955 where the engine was placed in the bomb bay of a J47-powered B-45. The J79 was lowered from the bomb bay and the four J47s were shut down leaving the B-45 flying on the single J79. The first flight after testing was on 17 February 1956, on a Lockheed F-104A Starfighter. While the engine proved highly successful from an operational standpoint, the Vietnam War experience showed the disadvantages of its highly visible, smoky exhaust when used to power military aircraft. It enjoyed a production run of more than 30 years. 16,950 J79s were built in the United States and under license in Israel, Canada, and Germany.
The J79 was replaced by the late 1960s in new fighter designs by afterburning turbofans such as the TF30 used in the F-111 and F-14, and newer generation turbofans with the P&W F-100 used in the F-15 Eagle which offer better cruise fuel economy by moving unburned air.
The J79 was used on the F-104 Starfighter, B-58 Hustler, F-4 Phantom II, A-5 Vigilante, IAI Kfir. A downgraded version of the F-16 with a J79 was proposed as a low-cost fighter for export, but found no customers. A simplified civilian version, designated the CJ-805, powered the Convair 880 and Convair 990 airliners.
In the F-104 and the F-4, the J79 made a unique howling sound at certain throttle settings. The sound is thought to be due to airflow in the exhaust section of the engine being disturbed by the engine bypass flaps. This led some pilots to call the F-104 Howling Howland.
In a photo shoot of aircraft with GE jet engines, including the J79, a F-104 collided with one of the few XB-70 test aircraft resulting in a massive crash and fatalities. This led to an end to publicity photo shoots of this nature.
Like its host F-4 Phantom II, the J79 will be remembered as one of the most successful aviation products to come out of the 1950s and 1960s.
It is speculated that J79s from wrecked US aircraft in the Vietnam War served as the basis for the Soviet Lyulka AL-21 jet engine.
Many J79 engines have found uses as gas turbine power generators in remote locations, in applications such as the powering of pipelines.
[edit] Specifications (J79-GE-17)
General characteristics
- Type: Afterburning turbojet engine
- Length: 17.4 ft (5.3 m)
- Diameter: 3.2 ft (1.0 m)
- Dry weight: 3,850 lb (1,750 kg)
Components
- Compressor: 17-stage axial compressor with variable stator vanes
Performance
- Thrust: 11,905 lbf (52.9 kN) dry; 17,835 lbf (79.3 kN) with afterburner
- Overall pressure ratio: 13.5:1
- Turbine inlet temperature: 1,210 °F (655 °C)
- Specific fuel consumption: 1.965 lb/(h·lbf) (200 kg/(h·kN)) with afterburner
- Thrust-to-weight ratio: 4.6:1 (45.4 N/kg)
[edit] References
- Neumann, Gerhard (June 1984). Herman the German (in English). William Morrow & Co, 269. ISBN 0688016820. “The former enemy alien and Air Corps G.I. whose inventive skills and maverick management techniques made jet engine history”
