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26-722: The J57/JT3C was developed into the J52 turbojet, the J75/JT4A turbojet, the JT3D/TF33 turbofan , and the XT57 turboprop (of which only one was built). The J57 and JT3C saw extensive use on fighter jets , jetliners , and bombers for many decades. The J57 was a development of the Pratt & Whitney XT45 (PT4) turboprop engine that was originally intended for the Boeing XB-52 . As

52-736: A higher overall pressure ratio. In a two-spool arrangement, the first compressor, usually called Low Pressure Compressor (LPC), is driven by the Low Pressure Turbine (LPT), and supercharges another unit known as the High Pressure Compressor (HPC) itself driven by the High Pressure Turbine (HPT). During starting the HP spool starts to rotate first, while the LP spool is stationary. As the HP spool accelerates and

78-637: A seven-stage high pressure unit. Behind the compressor is a nine-unit can -annular combustion chamber and a two-stage split turbine. In 1960, U.S. Air Force's Strategic Air Command (SAC) developed procedures so that the Boeing B-52 Stratofortress could use the Hound Dog's J52 engine for additional thrust while the missile was located on the bomber's two pylons. This helped heavily laden B-52s fly away from their airbases faster, which would have been useful in case of nuclear attacks on

104-653: Is the only model remaining in United States Air Force service. It is expected to remain as a mainstay of the Air Force heavy bomber fleet until at least 2040, with options for replacing the 8 TF33 engines with more modern equivalents being considered. In April 2020, the USAF released a request for proposals for 608 commercial replacement engines, with the plan to award the contract in May 2021. In September 2021,

130-794: The A-6 Intruder and the AGM-28 Hound Dog cruise missile. As of 2021 the engine was still in use in models of the A-4 Skyhawk . The engine is the basis for the Pratt & Whitney JT8D , a popular civilian low-bypass turbofan engine. The J52 was developed in the mid-1950s for the US Navy as a scaled-down derivative of the J57/JT3A . It was initially intended to power the A4D-3 Skyhawk , an advanced avionics model that

156-598: The Concorde . Within a few months, both P&W and Bristol had had a first run of their prototypes. Both demonstrated superb handling. Today, most civil and military turbofans have a two spool configuration, a notable exception being the Rolls-Royce Trent turbofan series which has three spools. Incidentally, most modern civil turbofans use all three of the above options to handle the extremely high overall pressure ratios employed today (50:1 typically). During

182-597: The 1950s the J57 was an extremely popular engine, with numerous military applications. Production figures were in the thousands, which led to a very reliable engine. Consequently, it was only natural for Boeing to choose the J57 civil variant, the JT3C, for their 707 jetliner. Douglas did likewise with their DC-8. Pressure to reduce jet noise and specific fuel consumption later resulted in P&;W using an innovative modification to convert

208-507: The B-52 power requirements grew, the design evolved into a turbojet , the JT3. Pratt & Whitney designed the J57 to have a relatively high overall pressure ratio to help improve both thrust-specific fuel consumption and specific thrust , but it was known that throttling a single high-pressure-ratio compressor would cause stability problems. As Sir Stanley Hooker explains in his autobiography,

234-504: The JT3C and JT4A turbojets, and the improved efficiency of the turbofan soon attracted the airlines. A JT3D-powered 707-123B and 720-023B (the suffix B was to indicate a turbofan-powered aircraft) entered service with American Airlines on the same day, March 12, 1961. The Boeing KC-135 Stratotankers were all originally powered by turbojet engines. With the demise of many airline 707s, the United States Air Force took

260-622: The JT3C turbojet into the JT3D two spool turbofan, initially for civil purposes, but also for military applications like the Boeing B-52H . The prestigious Collier Trophy for 1952 was awarded to Leonard S. Hobbs , chief engineer of United Aircraft Corporation , for "designing and producing the P&W J57 turbojet engine". The engine was produced from 1951 to 1965 with a total of 21,170 built. Many J57 models shipped since 1954 contained 7-15% of titanium, by dry weight. Commercially pure titanium

286-504: The JT3D, while 354 were fitted with CFM International CFM56 engines, which provide greater thrust, lower fuel consumption, and increased operational flexibility due to their lower noise footprint. The noise of the JT3D is one of the reasons NATO has debated re-fitting their E-3 Sentry AWACS fleet, since the aircraft are subject to restrictions that aircraft with modern engines are not. Operational flexibility would be further increased due to

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312-523: The World 1964/65, Aircraft engines of the World 1957 Data from Data from Flight Related development Comparable engines Related lists Pratt %26 Whitney J52 The Pratt & Whitney J52 (company designation JT8A ) is an axial-flow dual-spool turbojet engine originally designed for the United States Navy , in the 40 kN (9,000 lbf ) class. It powered

338-624: The YA2F-1 (YA-6A) Intruder, had a unique nozzle that could be angled downward at 23 degrees for STOL takeoffs; this was not used on production A-6s. Returning full circle, the J52 was selected to power the A4D-5, another model of the A-4 Skyhawk, remaining in all subsequent new-built models. The twin-spool J52 employs a split 12-stage axial compressor consisting of a five-stage low pressure unit and

364-511: The ability of higher power engines to increase the ceiling of the aircraft, extending the horizon for radar surveillance; for instance, RAF , French and Saudi E-3s routinely fly higher than NATO/USAF counterparts. In 1961, the TF33-powered Boeing B-52H Stratofortress entered service. The "H" model of the B-52 was the only production variant of the heavy bomber to be fitted with turbofan engines, and

390-531: The bases. The Hound Dog could then be refueled from the B-52's wing fuel tanks. Data from Flight Related development Comparable engines Related lists JT3D The Pratt & Whitney JT3D is an early turbofan aircraft engine derived from the Pratt & Whitney JT3C . It was first run in 1958 and was first flown in 1959 under a B-45 Tornado test aircraft. Over 8,000 JT3Ds were produced between 1959 and 1985. Most JT3D engines still in service today are used on military aircraft, where

416-559: The compressor 3) splitting the compressor into two units, one of which supercharges the other, with both units being mounted on separate shafts and driven by their own turbine GE adopted the second option with their General Electric J79 , while Pratt & Whitney adopted the two-spool arrangement with their J57. P&W realized that if they could develop a modest pressure ratio (< 4.5:1) axial compressor to handle adequately at any throttle setting including starting and acceleration, they could put two such compressors in series to achieve

442-400: The compressor to stall and vibrate. The compressor surges, which normally means the airflow reverses direction, causing a sharp drop in thrust. By the late 1940s, three potential solutions to the stability problem had been identified: 1) bleeding any excess compressed air at part speed overboard through interstage blow-off valves 2) incorporating variable geometry in the first few stages of

468-610: The design HP shaft speed significantly higher than that of the LP shaft. Any reductions in compressor diameter going towards the combustor exaggerates the difference. In the same timeframe as the J57, the Bristol Aeroplane Company Engine Division in the UK also adopted the two-spool arrangement into their Olympus turbojet engine series, which went on to propel the Avro Vulcan bomber and later

494-588: The engine is referred to by its US military designation of TF33 . Aware of the competition from the Rolls-Royce Conway turbofan, Pratt & Whitney decided to develop the JT3D turbofan from the JT3C turbojet for later deliveries of the Boeing 707 and the Douglas DC-8, then nearing entry into service. A 2-stage fan replaced the first 3 stages of the 9-stage JT3C LP compressor. On the LP turbine,

520-518: The fuel:air mixture in the combustor lights up, at some point there is sufficient energy in the turbine gas stream to start to rotate the LP spool, which accelerates, albeit more sluggishly. Eventually, at full throttle, both spools will rotate at their design speeds. Because the exit temperature of the HPC is obviously higher than that of the LPC, a similar blade tip Mach number for both units is achieved by making

546-607: The opportunity to buy the surplus airframes and use the engines to re-fit the KC-135As used by the Air National Guard and reserve squadrons with the civilian JT3D (designated TF33-PW-102). Over 150 aircraft were modified and the former KC-135A was re-designated the KC-135E. After long service for both airlines and air forces, the number of JT3D-powered aircraft is steadily decreasing. One hundred thirty five KC-135s use

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572-404: The outlet area of a compressor is significantly smaller than that of its inlet, which is fine when operating at the design pressure ratio, but during starting and at low throttle settings the compressor pressure ratio is low so ideally the outlet area should be much larger than its design value. Put crudely the air taken in at the front cannot get out the back, which causes the blades at the front of

598-520: The second stage was enlarged and a third stage added. Unlike GE with the CJ805-23, Pratt & Whitney had not undertaken any transonic fan research prior to designing the JT3D, so they were unable to incorporate a single stage unit into the specification. Instead P&W designed a 2-stage unit based on some research they had done to support the J91 nuclear turbojet. On the Boeing 707 the JT3D fan nacelle

624-494: Was canceled in 1957. After being canceled, the U.S. Air Force selected the J52 to power the AGM-28 Hound Dog cruise missile. The engine was designed with several unique features for this application, including a "conical centerbody mounted in the intake" and a "variable central plug ... in the nozzle". Then, in 1958, the US Navy selected the engine to power what became the A-6 Intruder . The J52-P-6 model, designed for

650-519: Was relatively short, whereas the Douglas DC-8 installation had a full-length fan cowl. Pratt & Whitney provided a kit whereby JT3Cs could be converted to the JT3D specification, and performance, during an overhaul. In 1959, important orders for the engine were the Boeing 707-120B and Boeing 720B when American Airlines ordered one 707 powered by JT3D turbofans and KLM ordered a JT3D-powered Douglas DC-8 . Earlier 707s and DC-8s had been powered by

676-406: Was used in the inlet case and low-pressure compressor case, whereas the low-pressure rotor assembly was made up of 6Al-4V titanium alloy blades, discs and disc spacers. Titanium alloys used in the J57 in the mid-50s suffered hydrogen embrittlement until the problem was understood. On May 25, 1953, a J57-powered YF-100A exceeded Mach 1 on its first flight. Data from: Aircraft Engines of

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