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Allison T56

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T56 / Model 501
A T56 mounted on a U.S. Air Force C-130 Hercules receives maintenance.
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

TheAllison T56is an American single-shaft, modular design militaryturbopropwith a 14-stage axial flowcompressordriven by a four-stage turbine. It was originally developed by theAllison Engine Companyfor theLockheed C-130 Herculestransport[3]entering production in 1954. It has been aRolls-Royceproduct since 1995 when Allison was acquired by Rolls-Royce. The commercial version is designated501-D.Over 18,000 engines have been produced since 1954, logging over 200 million flying hours.[4]

Design and development[edit]

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

The T56 turboprop, evolved from Allison's previousT38series,[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 theLockheed C-130 Herculesmilitary transport aircraft,the T56 was also installed on theLockheed P-3 Orionmaritime patrol aircraft(MPA),Grumman E-2 Hawkeyeairborne early warning(AEW) aircraft, andGrumman C-2 Greyhoundcarrier onboard delivery(COD) aircraft, as well as civilian airliners such as theLockheed Electraand theConvair 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]

Over the years, there have been a number of engine development versions, which are grouped by series numbers. The Series I collection of derivatives came out in 1954, producing a sea-level static power rating of 3,460 propeller shp (2,580 kW) at a 59 °F (15 °C; 519 °R; 288 K) ambient temperature. Successive engine follow-ups included the Series II, which was introduced in 1958 and had an increased power rating of 3,755 prop shp (2,800 kW), and the Series III, which came out in 1964 and had another power increase to 4,591 prop shp (3,424 kW). The Series II and III derivatives were developed under military component improvement programs (CIP).[7]By 1965, Allison was proposing the development of Series IV derivatives,[8]but in 1968, theUnited States Congressrestricted CIP work to reliability and maintainability improvements instead of performance improvements.[7]The Series IV derivatives were finally developed in the 1980s after being approved for aU.S. Air Forceengine 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 forNAVAIR's E-2C and C-2A aircraft, 501-D39 for theLockheed L-100aircraft, and the 501-K34 marineturboshaftforNAVSEA.The T56-A-427 was capable of 5,912 prop shp (4,409 kW), but it wastorque-limited to 5,250 prop shp (3,910 kW).[9]

TheLockheed Martin C-130J Super Herculeswhich first flew in 1996, has the T56 replaced by theRolls-Royce AE 2100,which uses dual FADECs (Full Authority Digital Engine Control) to control the engines and propellers.[10]It drives six-bladedscimitar propellersfromDowty 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 III engines.[13]As part of the T56 Series 3.5 upgrade, parts from the T56 Series IV engine (such as the compressor seals) and the uncooled turbine blades from theAE 1107Cturboshaft would be retrofit into existing T56 Series III casing installations.[14]Propeller upgrades to eight-bladed NP2000 propellers fromUTC Aerospace Systemshave been applied to the E-2 Hawkeye, C-2 Greyhound, and older-model C-130 Hercules aircraft,[15]and will be adopted on the P-3 Orion.[16]

Production of the T56 engine is expected to continue to at least 2026, with the U.S.Naval Air Systems Command(NAVAIR) order in 2019 of 24 additionalE-2D Advanced Hawkeyes(AHEs) powered by the T56-A-427A engine variant.[17]

Experimental and non-turboprop uses[edit]

The T56/Model 501 engine has been used in a number of experimental efforts, and as something other than a turboprop powerplant. In early 1960, two Allison YT56-A-6 experimental turbine engines without propellers were added next to existing propulsion engines onflight testsof a Lockheed NC-130B 58-0712 aircraft. The YT56-A-6 produced pressurized air for blowing over control surfaces to demonstrateboundary layer control(BLC), which helped to enableshort takeoff and landing(STOL) performance.[18]: 42–44 In 1963, Lockheed and Allison designed another STOL demonstrator, this time for aU.S. Armyrequirement. Lockheed internal designation GL298-7 involved a C-130E Hercules that was re-engined with 4,591 shp (3,424 kW) 501-M7B turboprops. The 501-M7B produced more power than the normally installed, 3,755 shp (2,800 kW) T56-A-7 engines by about 20% (though the 501-M7B was limited to 4,200 shp (3,100 kW) to avoid additional structural changes), because the introduction of air cooling in the turbine's first-stage blade and the first and second-stage vanes allowed for an increase in the turbine inlet temperature.[19]

In 1963, anaeroderivativeline of industrial gas turbines based on the T56 was introduced in under the 501-K name.[20]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.[21]Series II standard turbines included thenatural gas-fueled 501-K5 and the liquid-fueled 501-K14. The air-cooled Series III turbines included the natural gas-fueled 501-K13 and the liquid-fueled 501-K15.[22]A marinized turboshaft version of the 501-K is used to generate electrical power onboard all the U.S. Navy's cruisers (Ticonderogaclass) and almost all of its destroyers (Arleigh Burkeclass).

During the late 1960s, the U.S. Navy funded the development of the T56-A-18 engine, which introduced a new gearbox compared with the early gearbox on the T56-A-7.[23]The 50-hour preliminary flight rating test (PFRT) was completed for the T56-A-18 in 1968.[24]In the early 1970s,Boeing Vertolselected Allison (at that time known as the Detroit Diesel Allison Division (DDAD) ofGeneral Motors) to power a dynamic-system test rig (DSTR) supporting the development of itsXCH-62heavy-lift helicopter (HLH) program for the U.S. Army, using the Allison 501-M62B turboshaft engine.[25]The 501-M62B had a 13-stage compressor based on the 501-M24 demonstrator engine, which was a fixed single-shaft engine with an increasedoverall pressure ratioand a variable-geometry compressor, and it had anannular combustorbased on the T56-A-18 and other development programs. The turbine was derived from the fixed single-shaft T56, which had a four-stage section in which the first two stages provided enough power to drive the compressor, and the other two stages offered enough power to drive the propeller shaft. For the double-shaft 501-M62B engine, it was split into a two-stage turbine driving the compressor, where the turbine stages had air-cooled blades and vanes, and a two-stage free power turbine driving the propeller through a gearbox. The 501-M62B also incorporated improvements proven by Allison's GMA 300 demonstrator program, which allowed for an airflow of 42 lb/s (1,100 kg/min).[26]After DSTR testing was successful, the 501-M62B engine was further developed into theXT701-AD-700 engine for use on the HLH. The 8,079 shp (6,025 kW) XT701 passed the tests required to enter ground and flight testing on the HLH,[27]but funding of the HLH program was canceled in August 1975, when the triple-turbine, tandem-rotor helicopter prototype had reached 95% completion.[28]: 3 

Following the HLH program cancellation, Allison decided in early 1976 to apply the XT701 engine technology into a new industrial gas turbine product, the 570-K. The industrial engine, which entered production in the late 1970s, was derated to 7,170 shp (5,350 kW) and adapted for marine, gas compressor, and electrical power generation variants.[27]The only major changes made for the 570-K were the elimination of compressorbleed airand replacing the XT701's titanium compressor case with a steel case. The 570-K was then adapted to the 6,000 shp (4,500 kW) 501-M78B demonstration engine, which Lockheed flew on aGrumman Gulfstream IIas part of the NASA Propfan Test Assessment Program in the late 1980s. The 501-M78B had the same 13-stage compressor, combustor, 2-stage gas producer turbine, and 2-stage free power turbine used on the XT701 and 570-K, but it was connected through a 6.797 reduction ratio gearbox to a 9 ft diameter (2.7 m)Hamilton Standardsingle-rotationpropfan,containing propfan blades that were swept back 45 degrees at the tips.[29]

Variants[edit]

Main article:Allison T56 variants

The T56 has been developed extensively throughout its production run, the many variants are described by the manufacturer as belonging to four main series groups.

Initial civil variants (Series I) were designed and produced by theAllison Engine Companyas the 501-D and powered theLockheed C-130 Hercules.Later variants (Series II, III, and IV) and the Series 3.5 engine enhancement kit gave increased performance through design refinements.

Further derivatives of the 501-D/T56 were produced asturboshaftsforhelicoptersincluding a variant designated T701 that was developed for the canceledBoeing Vertol XCH-62project.

Applications[edit]

Specifications (T56 Series IV)[edit]

Data fromRolls-Royce.[30]

General characteristics

Components

Performance

  • Maximum power output:SLS, 59 °F (15 °C), max power:5,912 shp (4,409 kW) (torquelimited to 5,250 shp (3,910 kW));25,000 ft altitude (7,600 m),Mach0.5, 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/(hp⋅h) (0.2127 kg/(hp⋅h); 0.2853 kg/kWh);25,000 ft altitude (7,600 m),Mach0.5, max continuous power:0.4200 lb/(hp⋅h) (0.1905 kg/(hp⋅h); 0.2555 kg/kWh)[9]
  • Power-to-weight ratio:2.75shp/lb(4.52kW/kg)

See also[edit]

Related development

Comparable engines

Related lists

References[edit]

  1. ^Proc, Jerry."CP-140 Aurora".Radio communications and signals: Intelligence in the Royal Canadian Navy.Retrieved25 August2020.
  2. ^"The world's number one large turboprop".Rolls-Royce plc.Retrieved25 August2020.
  3. ^abcd"Global Security T56".globalsecurity.org.Retrieved1 November2012.
  4. ^"T56: Power for the Hercules, Orion, Hawkeye and Greyhound"(PDF).Rolls-Royce plc.Archived fromthe original(PDF)on 7 February 2013.Retrieved25 August2020.
  5. ^"T56 test-bed: The Allison engine for the C-130 fitted to a Super Constellation".Flight.30 April 1954. p. 539.ISSN0015-3710.Archived fromthe originalon 27 December 2014.
  6. ^McKinnon, Phillip (September 2004)."The Rolls-Royce Allison T56 is fifty"(PDF).New Zealand Aviation News. Archived fromthe original(PDF)on 21 October 2014.Retrieved2 November2013.
  7. ^abLaughlin, T.P.; Toth, Joseph (18–21 March 1985)."T56 derivative engine in the improved E-2C"(PDF).Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery.ASME 1985 International Gas Turbine Conference and Exhibit. Houston, Texas, U.S.A.doi:10.1115/85-GT-176.ISBN978-0-7918-7938-2.OCLC7344649118.
  8. ^Olbina, Milan C., ed. (15 January 1965)."Dice sees anniversary as time to look ahead".AllisoNews.Vol. 24, no. 15. pp. 1,7.OCLC42343144.
  9. ^abcMcIntire, W.L. (4–7 June 1984)."A new generation T56 turboprop engine"(PDF).Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery.Turbo Expo: Power for Land, Sea, and Air. Vol. 2: Aircraft engine, marine, microturbines and small turbomachinery. Amsterdam, Netherlands.doi:10.1115/84-GT-210.ISBN978-0-7918-7947-4.OCLC4434363138.
  10. ^"AE 2100 turboprop: Power for the Hercules, Spartan, US-2 and SAAB 2000 AEW&C"(PDF).Rolls-Royce plc.Archived fromthe original(PDF)on 17 February 2013.Retrieved2 November2012.
  11. ^Smithsonian National Air and Space Museum."Propeller, variable-pitch, 6-blade, Dowty R391".Retrieved4 August2020.
  12. ^"NOAA 'Hurricane Hunters' first to get T56 series 3.5 engine enhancement".Aero News.14 November 2013.Retrieved1 December2013.
  13. ^Drew, James (10 September 2015)."USAF approves production of Rolls-Royce T56 Series 3.5 upgrade".FlightGlobal.Retrieved11 August2020.
  14. ^"US approves Rolls-Royce's T56 Series 3.5 engine upgrade for C-130H fleet".Airforce Technology.9 July 2014.Retrieved16 February2023.
  15. ^Trevithick, Joseph (8 January 2018)."USAF eyeing new props and upgraded engines to breathe extra life into old C-130Hs".The War Zone.The Drive.Retrieved4 August2020.
  16. ^Donald, David (17 July 2018)."New look for an old warrior".Farnborough Air Show.AINonline.Retrieved4 August2020.
  17. ^Donald, David (11 April 2019)."Advanced Hawkeye marches on".Defense.AINonline.Retrieved9 September2020.
  18. ^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.ISBN978-1-56347-576-4.OCLC50447726.
  19. ^Anderton, David A. (7 January 1963)."Power boost planned for STOL C-130".Aeronautical engineering.Aviation Week and Space Technology.Marietta, Georgia, U.S.A. pp. 54–55, 57.ISSN0005-2175.
  20. ^Zigmunt 1997,p.127.
  21. ^Allison Industrial Gas Turbines 1983.
  22. ^Bixler, G.W.; Clifford, H.J. (5–9 March 1967)."Gas turbine electrical power and steam generation at Allison Division of General Motors"(PDF).ASME 1967 Gas Turbine Conference and Products Show.ASME 1967 Gas Turbine Conference and Products Show. Houston, Texas, U.S.A.doi:10.1115/67-GT-42.ISBN978-0-7918-7988-7.OCLC8518878647.
  23. ^McIntire, W.L.; Wagner, D.A. (18–22 April 1982)."Next generation turboprop gearboxes"(PDF).Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery.Turbo Expo: Power for Land, Sea, and Air. Vol. 2: Aircraft engine, marine, microturbines and small turbomachinery. London, England, U.K.doi:10.1115/82-GT-236.ISBN978-0-7918-7957-3.OCLC8518954720.
  24. ^The 1969 aerospace year book(PDF).Aerospace Industries Association of America (AIA). 1969. p. 52.
  25. ^"H.L.H. 1975 flight test projected: Component technology program meeting development goal".Army Research and Development.Vol. 15, no. 1. January–February 1974. pp. 10–11.hdl:2027/msu.31293012265199.ISSN0004-2560.
  26. ^Woodley, David R.; Castle, William S. (16–18 October 1973).Heavy lift helicopter main engines.National Aerospace Engineering and Manufacturing Meeting.SAE Technical Papers.SAE Technical Paper Series. Vol. 1. Los Angeles, California, U.S.A.:Society of Automotive Engineers(SAE) (published February 1973).doi:10.4271/730920.ISSN0148-7191.
  27. ^abStinger, D.H.; Redmond, W.A. (1978). "Advanced gas turbine for marine propulsion model 570-K".SAE Technical Paper Series.Vol. 1.Society of Automotive Engineers(SAE) (published February 1978).doi:10.4271/780702.ISSN0148-7191.{{cite book}}:|journal=ignored (help)
  28. ^Boeing Vertol Company (April 1980).Heavy lift helicopter — Prototype technical summary(Report).OCLC227450087.alternate url
  29. ^Little, B. H.; Poland, D. T.; Bartel, H. W.; Withers, C. C.; Brown, P. C. (July 1989).Propfan test assessment (PTA): Final project report.Vol. NASA-CR-185138.hdl:2060/19900002423.OCLC891598373.alternate url
  30. ^Training manual: T56/501D Series III.Rolls-Royce plc.2003. pp. 8-1 to 8-24.
  31. ^"Type Certificate Data Sheet E-282".Federal Aviation Administration(FAA)(30th ed.).U.S. Department of Transportation(DOT). 25 July 2013.Retrieved11 August2020.

Bibliography[edit]

External links[edit]

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