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J57 / JT3C
	YJ57-P-3 cut-away demonstrator at USAF Museum
Type	Turbojet
National origin	United States
Manufacturer	Pratt & Whitney
First run	1950
Major applications	Boeing 707 ; Boeing B-52 Stratofortress; Boeing KC-135 Stratotanker ; Douglas F4D Skyray ; Douglas DC-8 ; McDonnell F-101 Voodoo ; North American F-100 Super Sabre ; Vought F-8 Crusader
Number built	21,170 built
Developed from	Pratt & Whitney XT45
Variants	Pratt & Whitney JT3D/TF33
Developed into	Pratt & Whitney J52 ; Pratt & Whitney J75/JT4A ; Pratt & Whitney XT57/PT5

The Pratt & Whitney J57 (company designation: JT3C) is an axial-flow turbojet engine developed by Pratt & Whitney in the early 1950s. The J57 (first run January 1950^[1]) was the first 10,000 lbf (45 kN) thrust class engine in the United States. It is a two spool engine.

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).^[2] The J57 and JT3C saw extensive use on fighter jets, jetliners, and bombers for many decades.

Design and development

The J57 was a development of the Pratt & Whitney XT45 (PT4) turboprop engine that was originally intended for the Boeing XB-52. As 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,^[3] 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 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 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 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 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 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 the Concorde. Within a few months, both P&W and Bristol had had a first run of their prototypes. Both demonstrated superb handling.^[4]^[5]^[6]

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 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 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 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.^[7]

Titanium alloys used in the J57 in the mid-50s suffered hydrogen embrittlement^[8]^: 412 until the problem was understood.

On May 25, 1953, a J57-powered YF-100A exceeded Mach 1 on its first flight.

Variants

Data from: Aircraft Engines of the World 1964/65,^[9] Aircraft engines of the World 1957^[10]

J57-P-1W: 11,400 lbf (51 kN) s.t with water injection (B-52A)
J57-P-1WA: As P-1W
J57-P-1WB: As P-1W
J57-P-2
YJ57-P-3: 8,700 lbf (39 kN) thrust, used in the Convair YB-60
J57-P-4A: 16,000 lbf (71.17 kN) thrust
J57-P-5
J57-P-6: 10,500 lbf (46.71 kN) thrust
J57-P-6B: 10,500 lbf (46.71 kN) thrust
J57-P-7: 14,800 lbf (65.83 kN) thrust
J57-P-8
J57-P-8A: 10,400 lbf (46.26 kN) thrust
J57-P-8B: 16,000 lbf (71.17 kN) thrust
J57-P-9
J57-P-9W: 14,800 lbf (65.83 kN) thrust
J57-P-10: 10,500 lbf (46.71 kN) thrust
J57-P-11: 9,700 lbf (43.15 kN) thrust, 14,800 lbf (65.83 kN) thrust
J57-P-12
J57-P-13: 14,880 lbf (66.19 kN) thrust
J57-P-15
J57-P-16: 16,900 lbf (75.17 kN) thrust
J57-P-19W: 12,100 lbf (53.82 kN) thrust with water injection
J57-P-20: 18,000 lbf (80.07 kN) thrust^[11]
J57-P-20A: 18,000 lbf (80.07 kN) thrust
J57-P-21: 17,000 lbf (75.62 kN) thrust
J57-P-23: 17,000 lbf (75.62 kN) thrust
J57-P-25: 15,000 lbf (66.72 kN) thrust
J57-P-27
J57-P-29W: 12,100 lbf (53.82 kN) thrust with water injection
J57-P-31
J57-P-37A
J57-P-39
J57-P-41
J57-P-43W: 13,750 lbf (61.16 kN) thrust
J57-P-43WA: 13,750 lbf (61.16 kN) thrust
J57-P-43WB: 13,750 lbf (61.16 kN) thrust^[11]
J57-P-59W: 13,750 lbf (61.16 kN) thrust
J57-F-13: Production by Ford
J57-F-19W: Production by Ford
J57-F-21: Production by Ford
J57-F-23: Production by Ford
J57-F-29W: Production by Ford
J57-F-31W: Production by Ford
J57-F-35: Production by Ford
J57-F-43: Production by Ford
J57-F-43W: Production by Ford
J57-P-53
J57-P-55
J57-F-59W: Production by Ford
X-176: Project designation of the JT3-8 prototype of the barrel type (meaning constant diameter LP/HP compressor case) design first run on 28 June 1949.^[12]
X-184: Project designation of the JT3-10A prototype of the barrel type design first run on 28 February 1950.^[12]
JT3-8: Dash 8 signifies 8:1 pressure ratio. One of the original barrel shaped prototypes, aka X-176.^[12]
JT3-10A: Dash 10 signifies 10:1 pressure ratio. One of the original barrel shaped prototypes, aka X-184.^[12]
JT3-10B: The prototype of the re-designed wasp-waisted (meaning reducing LP case diameter and constant HP diameter) JT3, first run on 21 January 1950 and re-designated JT3A.^[13]
JT3A: Early production/prototype re-designated from the JT3-10B wasp-waisted prototype.^[13]
JT3P: Prototype engines for the Boeing 367-80.^[14]
JT3C-2: Civilian derivative of the J57-P-43WB, 13,750 lbf (61.16 kN) thrust^[11]
JT3C-4
JT3C-5
JT3C-6: 13,500 lbf (60.05 kN) thrust^[11]
JT3C-7: 12,000 lbf (53.38 kN) thrust^[11]
JT3C-12: 13,000 lbf (57.83 kN) thrust^[11]
JT3C-26: Civilian derivative of the J57-P-20, 18,000 lbf (80.07 kN) thrust^[11]

Derivatives

JT3D/TF33:A turbofan derivative of the J57.^[11]
XT57/PT5: A 20 ft diameter (6.1 m),^[15] 15,000 hp (11,185 kW) turboprop intended for the Douglas C-132^[16]

Applications

J57 (Military)

JT3P

Boeing 367-80

JT3C (Civilian)

Engines on display

A J57 is on display at the Texas Air Museum - Stinson Chapter, San Antonio, Texas
A J57 cutaway is on display at the New England Air Museum, Bradley International Airport, Windsor Locks, CT.^[18]
A J57 cutaway is on public display at the Aerospace Museum of California. It is s/n 35 used on the XB-52 program.^{[citation needed]}
A J57 is on display at the Loring AFB museum, former Loring AFB Limestone Maine.^{[citation needed]}

Specifications (J57-P-23)

Data from ^{[citation needed]}

General characteristics

Type: Afterburning turbojet
Length: 244 in (6197.6mm)
Diameter: 39 in (990.6mm)
Dry weight: 5,175 lb (2,347 kg)

Components

Compressor: all-axial, 9-stage LP compressor, 7-stage HP compressor
Combustors: cannular, 8 flame tubes
Turbine: all-axial, single stage HP turbine, 2-stage LP turbine

Performance

Maximum thrust: 11,700 lbf (52.0 kN) dry, 17,200 lbf (76.5 kN) with afterburner
Overall pressure ratio: 11.5:1
Air mass flow: 165 lb/s (75 kg/s) at maximum power
Turbine inlet temperature: 1,600 °F (870 °C)
Specific fuel consumption: 2.10 lb/(lbf⋅h) (59 g/(kN⋅s)) with afterburner
Thrust-to-weight ratio: 2.26 dry / 3.32 with afterburner

Specifications (JT3C-7)

Data from Flight ^[19]

General characteristics

Type: civil turbojet
Length: 155in (3937mm)
Diameter: 39in (990.6mm)
Dry weight: 4,200lb (1905kg)

Components

Compressor: all-axial, 9-stage LP compressor, 7-stage HP compressor
Combustors: cannular, 8 flame tubes
Turbine: all-axial, single stage HP turbine, 2-stage LP turbine

Performance

Maximum thrust: 12,030 lbf (53.5 kN) @ take-off, SLS, ISA
Overall pressure ratio: 12.5:1
Air mass flow: 180 lb/s (81.65 kg/s)
Specific fuel consumption: 0.785 lb/(lbf⋅h) (22.2 g/(kN⋅s)) @ take-off, SLS, ISA; and 0.909 lb/(lbf⋅h) (25.7 g/(kN⋅s)) @ max cruise 3,550 pounds-force (15.8 kN), M0.85, 35,000 ft (11,000 m), ISA
Thrust-to-weight ratio: 2.86

References

Notes

^ The Engines of Pratt & Whitney: A Technical History" Jack Connors, AIAA Inc. 2010, ISBN 978-1-60086-711-8, p. 225
^ Gunston, p.167
^ "Not much of an Engineer:an autobiography" Sir Stanley Hooker, Airlife Publishing Ltd. 1984, ISBN 0 906393 35 3, p.103
^ "Not much of an Engineer:an autobiography" Sir Stanley Hooker, Airlife Publishing Ltd. 1984, ISBN 0 906393 35 3, p.142
^ "American Airlines Experience with Turbojet/Turbofan Engines" K. F. Whatley, The American Society of Mechanical Engineers. 1962, ASME 62-GTP-16, p.5
^ "Collier Trophy". www.aerofiles.com. Archived from the original on 14 January 2001. Retrieved 16 April 2018.
^ "Titanium in Aerospace Applications" RI.Jaffee, W.H Sharp and RS Nycum, Defence Metals Information Society. October 24, 1961, DMIC Memorandum 133, p.44
^ "Iroquois" Archived 2017-11-07 at the Wayback Machine a 1957 Flight article
^ Wilkinson, Paul H. (1964). Aircraft engines of the World 1964/65 (19th ed.). London: Sir Isaac Pitman & Sons Ltd.
^ Wilkinson, Paul H. (1957). Aircraft engines of the World 1957 (15th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 82–83.
^ ^a ^b ^c ^d ^e ^f ^g ^h Taylor, John W.R. FRHistS. ARAeS. (1962). Jane's All the World's Aircraft 1962-63. London: Sampson, Low, Marston & Co Ltd.
^ ^a ^b ^c ^d Gunston, Bill (2006). World Encyclopaedia of Aero Engines (5th ed.). Stroud: Sutton Publishing. p. 166. ISBN 978-0-7509-4479-3.
^ ^a ^b Kay, Anthony L. (2007). Turbojet: History and Development 1930-1960: Volume 2: USSR, USA, Japan, France, Canada, Sweden, Switzerland, Italy, Czechoslovakia and Hungary. Marlborough, Wiltshire: Crowood Press. p. 154. ISBN 978-1-86126-939-3.
^ The Engines of Pratt & Whitney: A Technical History,Jack Connors 2010,ISBN 978 1 60086 711 8, p.246
^ Jane's All the World's Aircraft 1958. Sampson Low, Marston & Company. 1957. p. 444. OCLC 852161925. Archived from the original on 2022-06-10. Retrieved 2020-05-20.
^ "First Douglas C-132 Details". Aviation Week. Vol. 65, no. 17. October 22, 1956. p. 35. ISSN 0005-2175.
^ Minidocavia Northrop, P.83
^ http://neam.org/index.php?option=com_content&view=article&layout=edit&id=1059 Archived 2020-10-27 at the Wayback Machine "Pratt & Whitney J57 (JTC3) Cutaway"
^ Flightglobal archive - Flight International, 27 November 1953 Archived 12 November 2017 at the Wayback Machine Retrieved: 04 March 2017

Bibliography

Taylor, John W.R. FRHistS. ARAeS. (1962). Jane's All the World's Aircraft 1962-63. London: Sampson, Low, Marston & Co Ltd.
Connors, Jack (2010). The Engines of Pratt & Whitney: A Technical History. Reston. Virginia: American Institute of Aeronautics and Astronautics. ISBN 978-1-60086-711-8.
Francillon, René J. McDonnell Douglas Aircraft since 1920. London: Putnam, 1979. ISBN 0-370-00050-1.
Gunston, Bill (2006). World Encyclopedia of Aero Engines, 5th Edition. Phoenix Mill, Gloucestershire, England, UK: Sutton Publishing Limited. ISBN 0-7509-4479-X.