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The Pratt & Whitney J57 Turbojet Engine

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The Pratt & Whitney J-57 was one of the most successful 1950s era jet engines built in the US. Approximately 26,000 engines, of all versions were built. The civilian designation was the JT-3C and was used on early model B-707s, B-720s, and DC-8s. The military version was used by the USAF, USN, and USMC. They were used on the B/RB-52A-G, KC/EC/RC/C/NC/NKC-135A,D,G,Q, and N, F-100A-F, F/TF-102A, A/EA/ERA-3A-D, B/EB-66B-D, F/RF-101A-F, A-4C-J, A/EA-6A-D, and other US military aircraft.

The engine came in afterburner (reheat) and non-afterburner versions. On "heavies" (B-52 and KC-135 versions) it was available with water injection to increase take-off rated thrust (TRT). Water injection was used for the initial 2 minutes of take-off, but there was also a "dry" TRT available for take-offs not requiring water injection. The water was "demineralized water", that was not suitable for drinking, alcohaul was not used in the J-57.

TRT was limited to 5 minutes of continous operation, after that, military rated thrust (MRT) could be used for 30 minutes. Normal rated thrust (NRT) could be used continously.

The J-57 was a pure turbo jet, it had no fan section, but was later modified with a low bypass fan section and that version was designated as the TF-33 for military engines or the JT-3D (and JT-8D for the improved version) versions are still in use today on a lot of different airplanes, including the B-52H, KC-135E, E-3A-C, B-707, DC-8, B-737-200, B-727-200, DC-9, MD-80 series, and others. Another derivitve engine that came out of the J-57 was the TF-30 used on the F/FB-111A-G, and the F-14A/B, as well as many other fighters.

On airplanes like the KC-135A/Q and B-52F/G the J-57 produced around 11,600lbs of dry thrust for a fully cowled engine. The addition of water injection added about 800lbs of additional thrust for a total of about 12,400lbs.

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In the KC-135A/Q we used 640 gallons of water during the 2 minutes water injection was used, the B-52 used 1280 gallons, as they had twice as many engines. In the KC-135 the water added 5,600lbs to the weight of the airplane. Water injection could be used, in the KC-135 only, down to 20 degrees F. This water was heated in the water tank, in the KC-135 through the use of 8 5KW heating elements. The water had to be heated to a minumum of 60 degrees F (15.6 degrees C) if the outside temp was 40 degrees F, or less to keep the water from turning into ice. The B-52 did not use water below 40 degrees F.

The J-57 was a "constant thrust engine". It could deliver it's full range of dry thrust between minus 40 degrees F and C to plus 100 degrees F (37 degrees C).

It was a very tough engine, compared to todays engines, and handled FOD very well. But it was very noisy. A heavy weight KC-135A using water injection was the loudest airplane in the USAF inventory (the B-52 had sound baffels in the tail pipes). At wet TRT, it generated up to 165 db!

 

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J-57

Pratt & Whitney, many years behind Westinghouse and General Electric in acquiring turbojet expertise, began to dominate the turbojet industry after its development of the JT3 (J57). The JT3 initially had better fuel economy and more than double the thrust of its competitors. The innovative design feature of Pratt & Whitney's engine was an axial compressor with a double shaft (also called a dual-rotor or two-spool), a feature that dramatically increased the efficiency of the compressor. This engine placed the company in the forefront of aircraft propulsion development. The J57 eventually powered the B-52, YB-60, F-l00, F-l0l, YF-l05A, KC-135, Boeing 707, F4D, and A3D, as well as the Snark missile

In March 1951 Pratt & Whitney began flight tests of its new 10,000-pound thrust J57 jet engine. The first two-spool turbojet engine in the world, the J57 achieved supersonic speed on a YF-100. The J57 featured a dual-rotor axial-flow compressor which allowed low fuel consumption over a wide operating range and improved the sluggish acceleration previously characteristic of jet engines. The control system of the J57 consisted of a hydro mechanical fuel control (HMFC or HMC) for dry-engine combustion chambers, a HMFC for the afterburner, and separate anti-ice and ignition controls. The J57 production engine was the world's first jet engine to develop 10,000 lbs. thrust.

It evolved from the T45 turboprop engine designed for the XB-52 program. Built originally by the Boeing Company, the NASA B-52 is powered by eight Pratt & Whitney J57-19 turbojet engines, each of which produce 12,000 pounds of thrust. As advances in the B-52 design dictated greater power requirements, the turboprop concept was discarded and the wasp-waisted J57 turbojet was developed. By 1949 the J57 turbojet engine (which made commercial jet transport economically feasible) demonstrated good specific fuel consumption.

This turbojet engine was used in three of the Century Series fighters (the F-100, F-101, and F-102). The Northrop XSM-62A Snark's propulsion consisted of One Pratt & Whitney J57-P-17 turbojet engine (10,500 lbs thrust); 2 Aerojet General solid-fuel booster rockets (130,000 lbs thrust each).

Fairchild, Bell, and Martin studied high-altitude reconnaissance airplanes in design studies conducted for the Air Force during the second half of 1953. All three used Pratt & Whitney J57-P19 engines. The Bell (X-16) and Martin (B57-D) designs were chosen for development, but only the latter was completed and flew as the RB-57F. The X-16 was the most blatant misuse of the X-vehicle designation system—it was simply an attempt to hide what would today be called a spy-plane. The X-16 was designed to be a high-altitude long-range reconnaissance aircraft. None were completed before the Lockheed U-2 successfully demonstrated its ability to perform the spy mission. The first X-16 was reportedly over 80 percent complete when it was cancelled. Although never built, the X-16 pioneered several notable advances in lightweight structure design, and also was the driving force behind the development of high-altitude versions of the J57 jet engine that would go on to power the U-2 and other aircraft. The U-2 was initially powered by the Pratt & Whitney J57-P-37A of 11,000 lbs. thrust, though later replaced by the more powerful J75-P-13 of 17,000 lbs. thrust for later models.

F-8 aircraft were built originally for the U.S. Navy by LTV Aerospace of Dallas, Texas. The aircraft had a wingspan of 35 feet, 2 inches; was 54 feet, 6 inches long; and was powered by a Pratt & Whitney J57 turbojet engine.

The KC-135’s original J57 engines were “smokers,” especially when water was injected to increase thrust. The J57, a great engine when introduced in the late 1950s, produced 13,700 pounds of thrust, while the CFM–56 produced approximately 22,000 pounds, an increase of almost 40 percent, along with improved specific fuel consumption. With increased performance, the CFM– 56 engines transformed the KC–135 into a new airplane.

Thrust reversers haven’t been around very long in the history of aviation. For the first 50 years airplanes were relatively light and they had big propellers out front which can add a lot of drag (or negative thrust) to help with stopping on the ground. With the emergence of large jet-powered aircraft in the late 1950s and early 1960s the problem of stopping was a serious engineering challenge. Engineers developed the thrust reverser systems of sliding sleeves and clamshell doors in the 1950s. The first two major engines to use this technology were the Pratt & Whitney JT-3 (Military J57) and the General Electric CJ805 (derived from the Military J79). The basic idea is to route the primary jet and fan section bypass air through a series of chutes and doors to propel it forward. These devices were complicated “Rube Goldberg” devices that had a lot of reliability and maintainability problems.

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The J57 production engine was the world's first jet engine to develop 10,000 lbs. thrust. It evolved from the T45 turboprop engine designed for the XB-52 program. As advances in the B-52 design dictated greater power requirements, the turboprop concept was discarded and the wasp-waisted J57 turbojet was developed. The J57 featured a dual-rotor axial-flow compressor which allowed low fuel consumption over a wide operating range and improved the sluggish acceleration previously characteristic of jet engines.

The same year that production began, 1953, America's highest aviation honor, the Collier Trophy, was awarded for the design and development of this engine. Using a J57, the North American YF-100A became the world's first fighter aircraft to reach supersonic speed in level flight, on its maiden flight on May 25, 1953. Later versions of the J57 and its commercial equivalent, the JT3, reached the 18,000 lbs. thrust level with an afterburner. When production ended in 1970, more than 21,000 of these engines had been built. In addition to the B-52 and F-100, the J57 (or JT3) powered the Vought F8U; Douglas F4D, F5D, and A3D; Boeing 707 and 720; Douglas DC-8; and numerous USAF aircraft including the KC-135, F-101A, and F-102A.

The J57 on display is a YJ57-P-3, the first series to go into production. Rated at 8,700 lbs. thrust, it served as the prototype for the higher-powered engines later used in B-52s. P-3s were also used in testing the Northrop XSM-62 Snark missile and the Convair XB-60, an all-jet development of the B-36. This engine was the 16th of the 95 P-3s built and was used in XB-52 testing.

 

 

Last Updated

02/10/2014

 

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