Wednesday, September 15, 2010

General Electric J79

The General Electric J79 was a single-spool turbojet engine which was developed for use in a variety of fighter aircraft. The J79 was produced by General Electric Aircraft Engines in the United States, and under license by several other companies worldwide. There was a simplified civilian version of the GE J79, which was designated the CJ805, powered the Convair 880, while an aft-turbofan derivative, the CJ805-23, powered the Convair 990 airliners and a single Sud Aviation Caravelle intended as a prototype for the US market.

General Electric manufactured more than 17,000 J79 jet engines at a cost of US$ 625,000 per unit. It first run onboard of an aircraft on May 20, 1955, in the B-45 bomber bomb bay. The J79 was lowered from the bomb bay and the four J47s were shut down leaving the B-45 flying on the single J79 for two hours. The J79 was used to power the F-104 Starfighter, B-58 Hustler, F-4 Phantom II, A-5 Vigilante, and the IAI Kfir, enjoying a production run of more than 30 years.

The GE J79 was a single-spool, axial-flow turbojet with a 17-stage compressor with a novel arrangement of variable stator blades which allow the engine to develop pressure similar to a twin-spool 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 turboshaft counterpart to the J79 was the LM1500, used for land and marine applications. Many J79 derived engines have found uses as gas turbines for power plants in remote locations, in applications such as the powering of pipelines.

Specification for the General Electric J79

Type: Afterburning turbojet engine
Compressor: 17-stage axial compressor with variable stator vanes
Diameter: 3.2 ft (1.0 m)Diameter: 3.2 ft (1.0 m)
Length: 17.4 ft (5.3 m)
Dry weight: 3,850 lb (1,750 kg)
Maximum thrust: 11,905 lbf (52.9 kN) dry; 17,835 lbf (79.3 kN) with afterburner Overall pressure ratio: 13.5:1Turbine inlet temperature: 1,210 °F (655 °C)
Specific fuel consumption: 1.965 lb/(h·lbf) (200 kg/(h·kN)) with afterburner