J79 Turbojet Engine
Published January 30, 2007
General Electric J79 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. Widely used on several types of aircraft, including the McDonnell Douglas F-4 Phantom II, Convair B-58 Hustler, Lockheed F-104 Starfighter, Israeli Aircraft Industries Kfir, and North American Rockwell A-5 Vigilante, 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 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. The production F-104 was capable of flying at Mach 1.8, while the twin-engined F-4 Phantom and the four-engined B-58 Hustler were both capable of flying at over twice the speed of sound.
This example of the J79 is the YJ79-GE-3, 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.