General Electric J79
Type	Turbojet
Manufacturer	General Electric Aircraft Engines
Designed by	Gerhard Neumann
Maiden flight	20 May 1955
Introduction	17 February 1956
Number built	>17,000 [1]
Unit cost	$624,727 (J79-GE-3, 1960)[2]

The General Electric J79 is an axial-flow turbojet engine built for use in a variety of fighter and bomber aircraft. Produced by General Electric Aircraft Engines and under license by other companies worldwide, it was one of the first US-designed engines to outperform designs from the United Kingdom, which had previously led in the jet field

 

Design And Development

 

The J79 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.

 

History

 

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J79-GE-3 and YF-104A Starfighter

The first flight of the engine was on 20 May 1955 where the engine was placed in the bomb bay of a J47-powered B-45C (48-009). The J79 was lowered from the bomb bay and the four J47s were shut down leaving the B-45 flying on the single J79.^[3] The first flight after testing was on 17 February 1956, powering the first pre-production Lockheed YF-104A Starfighter. ^[4] 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. Over 17,000 J79s were built in the United States and under license in Belgium, Canada, Germany, Israel, Italy and Japan.

The J79 was used on the F-104 Starfighter, B-58 Hustler, F-4 Phantom II, A-5 Vigilante and the 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 although a prototype aircraft was flown. A simplified civilian version, designated the CJ-805, powered the Convair 880 and a single Sud Aviation Caravelle intended as a prototype for the US market, while a turbofan derivative, the CJ-805-23, powered the Convair 990 airliners.

The J79 was replaced by the late 1960s in new fighter designs by afterburning turbofans such as the Pratt & Whitney TF30 used in the F-111 and F-14, and newer generation turbofans with the P&W F100 used in the F-15 Eagle which offer better cruise fuel economy by moving unburned air.

For their part in designing the J79 Gerhard Neumann and General Electric Aircraft Engines were jointly awarded the Collier Trophy in 1958, also sharing the honor with Clarence Johnson (Lockheed F-104) and the U.S. Air Force (Flight Records).^[5]

 

Technical Description

 

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J79 on display at the National Museum of the United States Air Force

The J79 is a single-spool 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.

In the F-104 and the F-4, the J79 makes 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 strange feature led to the NASA operated F-104B Starfighter, N819NA, being named Howling Howland.^[6]

The turboshaft counterpart to the J79 is the LM1500, used for land and marine applications. Many J79 derived engines have found uses as gas turbine power generators in remote locations, in applications such as the powering of pipelines.

 

Notes

1. General Electric - Aviation History Retrieved: 7 April 2008
2. Pace 1992, p. 33.
3. Pace 1992 p. 67.
4. Pace 1992, p. 23.
5. Collier Trophy winners, 1950-1959, National Aeronautic Association. Retrieved: 7 April 2008
6. Bashow 1986, p. 16.
7. Pace 1992, p. 69.

Bibliography

• Neumann, Gerhard (June 1984). Herman the German (in English). William Morrow & Co, 269. ISBN 0-688-01682-0. “The former enemy alien and Air Corps G.I. whose inventive skills and maverick management techniques made jet engine history” 
• Pace, Steve. Lockheed F-104 Starfighter. Oscela, Wisconsin: Motorbooks International, 1992. ISBN 0-87938-608-8.
• Bashow, David L. Starfighter: A Loving Retrospective of the CF-104 Era in Canadian Fighter Aviation, 1961-1986. Stoney Creek, Ontario: Fortress Publications Inc., 1990. ISBN 0-91919-512-1.

Wikipedia

 

 

The J73 Turbojet  Engine

 

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J79 on display at the National Museum of the United States Air Force

Sectioned compressor stage of a J79.

Turbine stage of a J79.

General Electric's answer to Pratt & Whitney's JT3 (J57) was the J79, with an innovative compressor with variable stators. General Electric’s approach was to design a single spool 17 stage axial flow compressor with variable stators to prevent rotor blades from stalling. These controllable stators, or the variable geometry compressor as it came to be known, were the foundation for the J79 series of military engines. Pratt & Whitney used a successful high pressure ratio (12:1) design consisting of two separate compressors in series (one with nine stages and one with seven stages). The two compressors ran at different rotational speeds and were only aerodynamically coupled.

The development of the J79 turbojet began in 1952 as a more powerful follow-up to the General Electric J47 turbojet. The General Electric J79 engine was a high-performance single-shaft turbojet that featured variable-incidence stator blades in the later high-pressure stages of its seventeen-stage compressor. The J79 turbojet, the first high-compression variable-stator engine built in United States by GE, powered most Mach 2 U.S. aircraft, including the F-104, B-58, F11F-1F, F4H, and A3J, as well as the Regulus II missile. The production F-104 was capable of flying at Mach 1.8, while the twin-engine F-4 Phantom and the four-engine B-58 were both capable of flying at over twice the speed of sound. The engine has seen decades of faithful service and has stood the test of time.

Widely used on several types of aircraft, including the Israeli Aircraft Industries Kfir, more than 17,000 examples of the J79 were built in its thirty-year production run. In its long and successful career the dependable J79 accumulated well over 30 million flying hours and probably clocked more supersonic flying time than any other Western military aircraft engine produced during the Cold War. Civilian variants of the J79 also powered the Convair 880 and 990 airliners.

The J79 was developed as an outgrowth of the General Electric J73 engine program and was known at first as the J73-GE-X24A. The X24A was designed for reliable Mach 2 performance with minimal required maintenance. Its innovative variable stator vanes, developed by General Electric engineer Gerhard Neumann, increased compressor air pressure and helped eliminate compressor stall. Variable-incidence stators allowed the single-shaft turbojet to develop high pressures similar to those of dual-shaft engines, but at significantly lighter weight. The introduction of the variable stator vane turned out to be one of the most important developments in the history of jet aircraft engines.

The YJ79-GE-3 is the prototype version of the engine first flight-rated in 1954 for installation in the pre-production YF-104. It is just over seventeen feet long, slightly more than three feet in diameter, weighs around 3,500 pounds, and produced around 9,000 pounds of dry thrust. In full afterburner the YJ79 generated around 15,000 pounds of thrust with a fuel flow rate of ten gallons per second. Later versions of the J79 weighed anywhere from 3,500 to 3,800 pounds and produced up to 17,900 pounds of thrust in full afterburner.

On March 4, 1954, Lockheed test pilot Tony LeVier had taken the XF-104 "Starfighter" into the air for the first time, but subsequent flights had quickly revealed that its original engine couldn’t propel the dramatic new interceptor to its required speeds. A very long fuselage contained the cockpit and fuel cells, landing gear, and a single Wright YJ65-W-6 turbojet engine. This was supported by a pair of extremely short, anhedral supersonic wings with sharp leading edges that had to be padded to protect ground crews.

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J79

This design had enormous promise, but subsequent flights soon revealed that the J65 could deliver a maximum speed of only Mach 1.79 (1,324 mph), approximately double that of the F-86 but still short of the Air Force’s requirement of Mach 2.0 or better. The designers soon responded with a much-refined version of the troubled plane. They stretched the already-long fuselage by 5 feet, 6 inches in order to accommodate a new General Electric J79 axial-flow engine with 4,000 pounds greater thrust.

The first flight of a J79-powered aircraft was on 17 February 1956 when the Lockheed F-104A flew for the first time. Engine troubles cut the first flight short, but within a month the aircraft easily passed Mach 1 on the power of its single J79 engine. Built by Lockheed and dubbed the "Starfighter", the F-104 is a single engine aircraft with a wing span of 21 ft., 11 in. Its engine is a General Electric J79 that delivers 15,800 lbs. of thrust with afterburner. The maximum speed of the F-104 is 1,320 mph, its cruise speed is 575 mph and its altitude limit is 58,000 ft. The F-104's big J79 engine and tiny wings led to its popular nickname, "the missile with a man in it."

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J79-15A at the USAF Museum

The four General Electric J79-5 turbojet engines, so vital to the B-58's development, consumed fuel in prodigious quantities, particularly at supersonic velocities. Each of them produced 10,000 pounds of military thrust and 15,600 pounds of thrust with maximum afterburner at standard sea level static conditions, revolutionary figures for the mid-'50s. Each J79 featured a hydraulically actuated inlet spike that extended or retracted to match airflow velocity, keeping the conical shock wave outside the engine inlet during supersonic flight. Internally, the engine had variable position stator vanes in the first six stages of the compressor, which adjusted in pitch automatically as a function of engine speed and compressor inlet temperature, to minimize the possibility of compressor stall. An adjustable exhaust nozzle incorporated slatted vanes that opened and closed, depending on throttle, to give the most efficient thrust and specific fuel consumption.

Between fiscal years 1985 and 1994, the Air Force reduced its F-4 aircraft inventory from 1,597 to 61. Depot overhauls of the J79 engine, which powered the F-4 aircraft, also declined from over 500,000 direct labor hours in fiscal year 1986 to an estimated 0 for fiscal year 1997.

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