Air Force Museum
J47 Turbojet
The General Electric J47 powered many of the aircraft that defined the first decade of American jet aviation. Installed in fighters, bombers, reconnaissance aircraft, and the B-36’s auxiliary pods, the engine helped turn experimental jet flight into an industrial and operational system. Its broad use also simplified training and maintenance across a rapidly expanding force.
In depth
History & service
The J47 was developed by the General Electric Co. from the earlier J35 engine and was first flight-tested in May 1948 as a replacement for the J35 used in the North American XF-86 Sabre. In September 1948 a J47 powered an F-86A to a new world's speed record of 670.981 mph. More than 30,000 engines of the basic J47 type were built before production ended in 1956.
The engine was produced in at least 17 different series and was used to power such USAF aircraft as the F-86, XF-91, B-36, B-45, B-47 and XB-51.
A J47-GE-7 engine became the first axial-flow (straight-through airflow) engine in the United States to be approved for commercial use. The J47 was retired when the last Boeing KC-97J was dropped from Air National Guard service in 1978, thus spanning 30 years of operational service. The engine on display is a J47-GE-25 and is the type used on a variety of B-47B, E, H, K and L series aircraft. Part of the case has been cut away to reveal the engine's internal components.
Details that tell the story
Axial-flow turbojet · Powered aircraft including the F-86 and B-47 · Produced in very large numbers
The aircraft in figures
Model: J47-GE-25 · Compressor: 12-stage axial · Turbine: Single-stage axial · Weight: 2,707 lbs. · Thrust: 5,670 lbs. · Maximum rpm: 7,950 · Maximum operating altitude: 50,000 ft.
The revolution inside the engine
A jet engine takes in air, compresses it, adds fuel, and uses the resulting hot gas to produce thrust. A turbine extracts enough energy from that gas to keep the compressor turning. The arrangement sounds straightforward, but the machinery lives in a difficult combination of heat, centrifugal force, pressure, and vibration. Early practical jets depended on advances in materials and manufacturing as much as on the basic idea.
The first generation offered great promise at high speed, but fuel consumption, engine life, and throttle response limited what aircraft could do with it. The transition did not immediately make propellers obsolete. Piston aircraft and turboprops remained effective where low-speed efficiency, endurance, or operating cost mattered more than maximum speed. Aircraft were built around missions, and different missions rewarded different engines.
Later turbofans moved a large quantity of air around the hot core, improving efficiency and changing the economics of airline travel. Military engines often accepted different compromises for acceleration, compact size, or supersonic performance. A display of engines therefore contains several parallel histories: the race for speed, the effort to carry more people at lower cost, and the persistent search for machinery that crews could trust. Cross-gallery comparisons reveal why engines that look broadly similar can represent very different priorities.
