Allison T56

The Allison T56 is an American single-shaft, modular design military turboprop with a 14-stage axial flow compressor driven by a four-stage turbine. It was originally developed by the Allison Engine Company for the Lockheed C-130 Hercules transport[3] entering production in 1954. It has been a Rolls-Royce product since 1995 when Allison was acquired by Rolls-Royce. The commercial version is designated 501-D. Over 18,000 engines have been produced since 1954, logging over 200 million flying hours.[4]

T56 / Model 501
Type Turboprop
National origin United States
Manufacturer Allison Engine Company
Rolls-Royce plc
Major applications Convair 580
Grumman C-2 Greyhound
Lockheed C-130 Hercules
Lockheed L-188 Electra
Lockheed P-3 Orion
Northrop Grumman E-2 Hawkeye
Lockheed CP-140 Aurora[1]
Number built >18,000[2]
Developed from Allison T38
Developed into Rolls-Royce T406

Design and development
Allison T56-A1 turboprop engine cutaway, at the Smithsonian National Air and Space Museum

The T56 turboprop, evolved from Allison's previous T38 series,[3] was first flown in the nose of a B-17 test-bed aircraft in 1954.[3] One of the first flight-cleared YT-56 engines was installed in a C-130 nacelle on Lockheed's Super Constellation test aircraft in early 1954.[5] Originally fitted to the Lockheed C-130 Hercules quad-turboprop military transport aircraft, the T56 was also installed on the Lockheed P-3 Orion quad-turboprop maritime patrol aircraft (MPA), Grumman E-2 Hawkeye twin-turboprop airborne early warning (AEW) aircraft, and Grumman C-2 Greyhound twin-turboprop carrier onboard delivery (COD) aircraft, as well as civilian airliners such as the quad-turboprop Lockheed Electra and the Convair 580.[3]

The T56-A-1 delivered to Lockheed in May, 1953, produced only 3,000 shp (2,237 kW), compared to the required 3,750 shp (2,796 kW) for the YC-130A. Evolution of the T56 has been achieved through increases in pressure ratio and turbine temperature. The T56-A-14 installed on the P-3 Orion has a 4,591 shp (3,424 kW) rating with a pressure ratio of 9.25:1 while the T56-A-427 fitted to the E-2 Hawkeye has a 5,250 shp (3,915 kW) rating and a 12:1 pressure ratio. In addition, the T56 produces approximately 750 lbf (3,336.17 N) residual thrust from its exhaust.[6]

In 1963, an aeroderivative line of industrial gas turbines based on the T56 was introduced in under the 501-K name.[7] The 501-K is offered as a single-shaft version for constant speed applications and as a two-shaft version for variable-speed, high-torque applications.[8] A marinized turboshaft version of the 501-K is used to generate electrical power onboard all the U.S. Navy's cruisers (Ticonderoga class) and almost all of its destroyers (Arleigh Burke class).

Over the years, there have been a number of engine development versions, which are grouped by series numbers. The Series I derivatives came out in 1954, followed by Series II in 1958 and Series III in 1964. The Series IV derivatives were developed in the 1980s after being approved for a U.S. Air Force engine model derivative program (EMDP) in the 1979 fiscal year budget. Series IV engines include the Air Force EMDP T56-A-100 demonstrator, model T56-A-101 for the Air Force's C-130 aircraft, T56-A-427 for NAVAIR's E-2C and C-2A aircraft, 501-D39 for the Lockheed L-100 aircraft, and the 501-K34 marine turboshaft for NAVSEA.[9]

The Lockheed Martin C-130J Super Hercules which first flew in 1996, has the T56 replaced by the Rolls-Royce AE 2100, which uses dual FADECs (Full Authority Digital Engine Control) to control the engines and propellers.[10] It drives six-bladed scimitar propellers from Dowty Rotol.[11]

The T56 Series 3.5, an engine enhancement program to reduce fuel consumption and decrease temperatures, was approved in 2013 for the National Oceanic and Atmospheric Administration (NOAA) WP-3D "Hurricane Hunter" aircraft.[12] After eight years of development and marketing efforts by Rolls-Royce, the T56 Series 3.5 was also approved in 2015 for engine retrofits on the U.S. Air Force's legacy C-130 aircraft that were currently in service with T56 Series 3 engines.[13] Propeller upgrades to eight-bladed NP2000 propellers from UTC Aerospace Systems have been applied to the E-2 Hawkeye, C-2 Greyhound, and older-model C-130 Hercules aircraft,[14] and will be adopted on the P-3 Orion.[15]

Variants
501-D10
The initial civil variant, which was proposed in 1955 with 3,750 equivalent shp (2,800 kW) of power at a brake specific fuel consumption (BSFC) of 0.54 lb/hp/h (0.24 kg/hp/h; 0.33 kg/kW/h), a two-stage gearbox with a reduction ratio of 12.5:1, a 14-stage axial flow compressor with a compression ratio over 9:1, a four-stage turbine, and a 13 1⁄2 ft diameter (4.11 m), three-blade Aeroproducts A6341FN-215 propeller[16]
501-D12
501-D13
(Series I) A 3,750 equivalent shp (2,800 kW) power rating at sea level takeoff, 14-stage axial compressor, 6 cannular combustion chambers, 4-stage turbine, and 13:54:1 propeller ratio, certified on September 12, 1957;[17] Lockheed L-188 Electra and Convair CV-580 (Replacing P&W R-2800) starting December 1957
501-D13A
(Series I) Similar to the 501-D13 but using a Hamilton Standard propeller; certified on April 15, 1958[17]
501-D13D
(Series I) Similar to the 501-D13 except for the location of the rear mount and using D.C. generator drive; certified on December 18, 1959[17]
501-D13E
(Series I) Similar to the 501-D13 except for the location of the rear mount; certified on December 18, 1959[17]
501-D13H
(Series I) Similar to the 501-D13D but with water-methanol injection; certified on February 20, 1964;[17] used on the USAF's General Dynamics NC-131H Samaritan[18]
501-D15
A 4,050 shp (3,020 kW) engine under development for the Lockheed Electra[19]
501-D22
(Series II) Similar to the 501-D13A but with 4,050 equivalent shp (3,020 kW) power rating at sea level takeoff, a shroud turbine, gearbox offset up, and no auto-feathering; certified on October 28, 1964;[17] Lockheed L-100 Hercules
501-D22A
(Series III); Similar to the 501-D22 but with 4,680 equivalent shp (3,490 kW) power rating at sea level takeoff and air-cooled first-stage turbine blades, vanes, and stalk blades in all four turbine stages; certified on January 23, 1968[17]
501-D22C
(Series III) Similar to the 501-D22A but with gearbox offset down, integral mount pads, and water-methanol injection; certified on December 27, 1968[17]
501-D22G
(Series III) Similar to the 501-D22C but with 4,815 equivalent shp (3,591 kW) power rating at sea level takeoff, a three-mount system, auto-feathering, and no water-methanol injection; certified on March 23, 1984[17]
501-D36A
(Series II) (non-type certified)
501-D39
(Series IV) Offered for the Lockheed L-100 civil aircraft[9]
501-M24
A demonstrator engine later used to derive the 501-M62B engine developed for the XCH-62 helicopter[20]
501-M25
A 6,000 shp (4,500 kW) four-stage fixed turbine engine similar to the T56-A-15, but with a 90 °F (32 °C) increase in maximum turbine inlet temperature rating to 1,970 °F (1,080 °C; 2,430 °R; 1,350 K) and a variable geometry compressor for the inlet vane and the first five stator vanes; investigated in 1965 to power helicopters with a 75,000–85,000 lb (34,000–39,000 kg) maximum takeoff weight (MTOW)[21]:12,15,213
501-M26
A 5,450 shp (4,060 kW) similar to the 501-M25 but with a free turbine instead of a fixed turbine, and a two-stage gas producer turbine[21]:12,15,213
501-M62B
An internal designation for the engine that became the 8,079-shaft-horsepower (6,025-kilowatt) T701-AD-700 turboshaft, which weighed 1,179 lb (535 kg) and was intended to power the Boeing Vertol XCH-62 heavy-lift helicopter; 15 engines built, 700 hours of component testing, and almost 2,500 hours of engine development testing completed before the helicopter project's cancellation[22]
501-M71
A derivative of the T56-A-14 evaluated by NAVAIR in 1982 to achieve 10% lower fuel consumption, 24% more horsepower, smokeless exhaust, and greater reliability[23]
501-M78
A 6,000 shp (4,500 kW), 9-foot diameter (2.7 m) demonstrator engine for NASA's Propfan Test Assessment program; flight-tested on a Gulfstream II aircraft[24]
501-M80C
Also known as the T406-AD-400, a 6,000 shp class (4,500 kW) turboshaft engine[25] primarily based on the T56-A-427, but with a free-turbine turboshaft added to the single-spool engine; used on the V-22 Osprey tiltrotor assault transport[26]
A T56 on a mobile test unit at MCAS Futenma, 1982
Maintenance of a T56-A-16, 2009
T56-A-1
T56-A-1A
A 3,750 equivalent shp (2,800 kW) engine used on the Lockheed C-130A Hercules[27]
T56-A-2
Proposed gas generator engines for the McDonnell XHCH-1 helicopter
T56-A-3
A 3,250 equivalent shp (2,420 kW) engine that was paired with an Aeroproducts propeller and test flown by the Military Air Transport Service (MATS) on a pair of Convair YC-131C twin-turboprop aircraft between January and December 1955[28]
T56-A-4
A 2,900 hp (2,200 kW) engine for the C-131D executive transport/VC-131H VIP transport;[29] also the proposed engines for the McDonnell XHRH-1 helicopter, with propeller drive and gas generator bleed for rotor-tip pressure jets
T56-A-5
A 2,100 shp (1,600 kW) turboshaft version for the Piasecki YH-16B Transporter helicopter
T56-A-6
Gas generator engines for the NC-130B (58-0712) boundary layer control (BLC) demonstrator[30]
T56-A-7
A 4,050 shp (3,020 kW) engine flight-tested on a U.S. Air Force Allison Boeing B-17 flying testbed aircraft, intended for the Lockheed C-130B[19]
T56-A-7A
(Series II) Lockheed C-130B Hercules Starting May 1959
T56-A-7B
(Series II) Similar to -A-7A
T56-A-8
(Series I) Entered production in 1959[23]
T56-A-9
(Series I)
T56-A-9D
(Series I) Lockheed C-130A Hercules starting December 1956 and on all Grumman E-2A Hawkeyes from 1960
T56-A-9E
(Series I) Similar to -A-9D
T56-A-10W
(Series I) Water injection model that entered production in 1960[23]
T56-A-10WA
(Series II)
T56-A-14
(Series III) Lockheed P-3/EP-3/WP-3/AP-3/CP-140 Aurora from August 1962; entered production in 1964[23]
T56-A-14A
(Series 3.5) Fuel efficiency and reliability upgrade, Lockheed WP-3D Orion from May 2015.
T56-A-15
(Series III) Lockheed C-130H Hercules USAF from June 1974
T56-A-15A
(Series 3.5)
T56-A-16
(Series III) Lockheed C-130H/R/T Hercules USN/USMC
T56-A-16A
(Series 3.5)
T56-A-18
Navy-funded development with air-cooled blades and vanes in the first two stages; 50-hour preliminary flight rating test completed in 1968;[31] introduced major gearbox update after 4,000 hours of back-to-back testing, featuring a double helical first gear stage, a planetary helical gear for the second stage, and fewer parts for the accessory gearing (compared with a first-stage spur gear, second-stage planetary spur gear, and separable clamped components in the accessory gearing for the T56-A-7 gearbox)[32]
T56-A-100
(Series IV) U.S. Air Force EMDP demonstrator[9]
T56-A-101
(Series IV) Offered for the Lockheed C-130 Hercules[9]
T56-A-422
Used on U.S. Navy Northrop Grumman E-2C Hawkeye aircraft[33]
T56-A-423
Used on U.S. Navy Lockheed EC-130G and EC-130Q aircraft[33]
T56-A-425
(Series III) Grumman C-2A Greyhound from June 1974
T56-A-427
(Series IV) Northrop Grumman E-2 Hawkeye upgrades from 1972
T56-A-427A
(Series IV) Northrop Grumman E-2D Advanced Hawkeye
T701-AD-700
(501-M62B) An 8,079 shp (6,025 kW) turboshaft powerplant intended for use on the canceled three-engine Boeing Vertol XCH-62 heavy-lift helicopter[34]

Applications

Specifications (T56 Series IV)

Data from Rolls-Royce.[35]

General characteristics

Components

Performance

  • Maximum power output: SLS, 59 °F (15 °C), max power: 5,912 shp (4,409 kW) (torque limited to 5,250 shp (3,910 kW)); 25,000 ft altitude (7,600 m), Mach 0.5, max continuous power: 3,180 shp (2,370 kW)[9]
  • Turbine inlet temperature: 860 °C (1,580 °F)
  • Fuel consumption: 2,412 lb/h (1,094 kg/h)
  • Specific fuel consumption: SLS, 59 °F (15 °C), max power: 0.4690 lb/shp/h (0.2127 kg/shp/h; 0.2853 kg/kW/h); 25,000 ft altitude (7,600 m), Mach 0.5, max continuous power: 0.4200 lb/shp/h (0.1905 kg/shp/h; 0.2555 kg/kW/h)[9]
  • Power-to-weight ratio: 2.75 shp/lb (4.52 kW/kg)

See also

Related development

Comparable engines

Related lists

References
  1. "Aurora".Retrieved April 2019
  2. "Rolls-Royce".Retrieved November 2018
  3. "Global Security T56". www.globalsecurity.org. Retrieved 1 November 2012.
  4. "Rolls Royce T56 Product Sheet" (PDF). www.rolls-royce.com. Archived from the original (PDF) on 2013-02-07. Retrieved 2012-11-02.
  5. https://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201209.html?search=april%20t56%20test-bed
  6. "The Rolls-Royce Allison T56 is fifty" (PDF). New Zealand Aviation News, September, 2004. Archived from the original (PDF) on 2014-10-21. Retrieved 2013-11-02.
  7. Zigmunt 1997, p. 127.
  8. Allison Industrial Gas Turbines 1983.
  9. McIntire, W.L. (June 4–7, 1984). A new generation T56 turboprop engine (PDF). Turbo Expo: Power for Land, Sea, and Air. 2: Aircraft engine; marine; microturbines and small turbomachinery. Amsterdam, Netherlands. doi:10.1115/84-GT-210. ISBN 978-0-7918-7947-4. OCLC 4434363138.
  10. "Rolls Royce AE-2100 Product Sheet" (PDF). www.rolls-royce.com. Archived from the original (PDF) on 2013-02-17. Retrieved 2012-11-02.
  11. Smithsonian National Air and Space Museum. "Propeller, variable-pitch, 6-blade, Dowty R391". Retrieved August 4, 2020.
  12. "NOAA 'Hurricane Hunters' first to get T56 series 3.5 engine enhancement". Aero News. November 14, 2013. Retrieved December 1, 2013.
  13. Drew, James (September 10, 2015). "USAF approves production of Rolls-Royce T56 Series 3.5 upgrade". FlightGlobal. Retrieved August 11, 2020.
  14. Trevithick, Joseph (January 8, 2018). "USAF eyeing new props and upgraded engines to breathe extra life into old C-130Hs". The War Zone. The Drive. Retrieved August 4, 2020.
  15. Donald, David (July 17, 2018). "New look for an old warrior". Farnborough Air Show. AINonline. Retrieved August 4, 2020.
  16. Stone, Irving (January 24, 1955). "T56 boosts U.S. turboprop airliner bid". Air transport. Aviation Week. Vol. 62 no. 4. pp. 80, 83. ISSN 0005-2175.
  17. Rolls-Royce Corporation (July 25, 2013). "Type Certificate Data Sheet E-282" (PDF) (30th ed.). Department of Transportation (DOT) Federal Aviation Administration (FAA). Retrieved August 11, 2020. Lay summary.
  18. "Test aircraft variants". Federation of American Scientists (FAS). Retrieved August 12, 2020.
  19. AIA Yearbook 1958, p. 121.
  20. Woodley, David R.; Castle, William S. (October 16–18, 1973). Heavy lift helicopter main engines. National Aerospace Engineering and Manufacturing Meeting. Los Angeles, California, U.S.A.: Society of Automotive Engineers (SAE) (published February 1973). doi:10.4271/730920. ISSN 0148-7191.
  21. Allison Division - General Motors (July 1965). Powerplant studies for shaft-driven helicopter (Report). OCLC 872723329.
  22. Stinger, D.H.; Redmond, W.A. (February 1978). "Advanced gas turbine for marine propulsion model 570-K". Society of Automotive Engineers (SAE). doi:10.4271/780702. ISSN 0148-7191. Cite journal requires |journal= (help)
  23. Cote, S.M. (June 17, 1983). Survey of P-3C mission profiles for development of the T56-A-14 duty cycle (Report). Naval Air Systems Command (NAVAIR). OCLC 38850276.
  24. Moxon, Julian (May 9, 1987). "Propfanned G2 takes to the air" (PDF). World News. Flight International. Vol. 131 no. 4061. Marietta, Georgia, USA. p. 2. ISSN 0015-3710.
  25. Competition Advocate General, Department of the Navy. Long range acquisition estimates (FY 88 base year projections) (Report). p. 154. hdl:2027/uiug.30112104099186. Retrieved August 1, 2020.
  26. "Navy surprise on V-22 power" (PDF). Propulsion. Flight International. Vol. 129 no. 3995. Detroit, Michigan, USA. January 25, 1986. p. 16. ISSN 0015-3710. Archived from the original (PDF) on April 19, 2014.
  27. The 1961 aerospace year book (PDF) (42nd ed.). American Aviation Publications. 1961. p. 400.
  28. Allen, Brooke E. (March 1957). "What we've learned about turboprops". Air Force Magazine. Vol. 40 no. 3. pp. 82, 85–86. ISSN 0730-6784.
  29. DeFrank, Thomas (July 2008). "The things it carried: How an unremarkable Convair C-131H transported cops, patients, prisoners, and Gerald Ford". Air & Space Magazine. ISSN 0886-2257.
  30. Norton, Bill (2002). STOL progenitors: The technology path to a large STOL aircraft and the C-17A. American Institute of Aeronautics and Astronautics (AIAA). pp. 42–43. doi:10.2514/4.868160. ISBN 978-1-56347-576-4. OCLC 50447726.
  31. The 1969 aerospace year book (PDF). Aerospace Industries Association of America (AIA). 1969. p. 52.
  32. McIntire, W.L.; Wagner, D.A. (April 18–22, 1982). Next generation turboprop gearboxes (PDF). Turbo Expo: Power for Land, Sea, and Air. 2: Aircraft engine; marine; microturbines and small turbomachinery. London, England, U.K. doi:10.1115/82-GT-236. ISBN 978-0-7918-7957-3. OCLC 8518954720.
  33. "Electronic aircraft variants". Federation of American Scientists (FAS). Retrieved August 12, 2020.
  34. "Army revises HLH program, sets competitive prototype tests". R&D News. Army Research and Development. Vol. 16 no. 2. March–April 1975. pp. 4–5. hdl:2027/osu.32435062846985. ISSN 0004-2560.
  35. Rolls, Royce . Training Manual . T56/501D Series III. Rolls-Royce, 2003. 8-1 To 8-24. Print.

Bibliography
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