Allison T56 variants#T701

;501-D10: The initial civil variant, which was proposed in 1955 with {{cvt|3,750|shp|kW|adj=pre|equivalent}} of power at a brake specific fuel consumption (BSFC) of {{cvt|0.54|lb/hph|kg/hph kg/kWh}}, 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 {{cvt|13+1/2|ft|m|adj=mid|diameter|sigfig=3}}, three-blade Aeroproducts A6341FN-215 propeller.{{cite magazine |issn=0005-2175 |magazine=Aviation Week |title=T56 boosts U.S. turboprop airliner bid |url=https://archive.org/details/Aviation_Week_1955-01-24/page/n40 |pages=80, 83 |publication-date=January 24, 1955 |given=Irving |surname=Stone |department=Air transport |volume=62 |number=4}}

;501-D13: (Series I) Commercial version of the T56-A-1 used on the Lockheed L-188 Electra, but using kerosene as the primary fuel and JP4 as the alternate (instead of JP4 as primary and gasoline as secondary), and with the gearbox reduction ratio increased to 13.54 from 12.5, which lowers the propeller blade tip speed by 8 percent to {{cvt|721|ft/s|m/s kn mi/h km/h}} for the {{cvt|13|ft|6|in|adj=mid}} Aeroproducts 606 propeller; {{cvt|3,750|shp|kW|adj=pre|equivalent}} power rating at sea level takeoff, 14-stage axial compressor, 6 cannular combustion chambers, and 4-stage turbine; 13,820 rpm shaft and {{cvt|1,780|F|C R K|adj=mid}} turbine inlet temperature;{{cite conference |issn=0148-7191 |title=The Allison power package for the Lockheed Electra |date=April 9–12, 1956 |given1=R.M. |surname1=Hazen |given2=D. |surname2=Gerdan |given3=R.R. |surname3=LaMotte |journal=SAE Technical Papers |series=SAE Technical Paper Series |volume=1 |conference=SAE National Aeronautic Meeting |location=New York City, New York, U.S.A. |publisher=SAE International |doi=10.4271/560273 |oclc=5817960717}} certified on September 12, 1957.{{cite web |title=Type Certificate Data Sheet E-282 |edition=30th |date=July 25, 2013 |url=https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/37851AD3AA37B87486257BB800525FC6 |publisher=U.S. Department of Transportation (DOT) |website=Federal Aviation Administration (FAA) |access-date=August 11, 2020}}

;501-D13A: (Series I) Similar to the 501-D13 but using a Hamilton Standard propeller; certified on April 15, 1958.

;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; used on the Convair CV-580 passenger aircraft.{{cite web |website=Kelowna Flightcraft Aerospace |title=Convair 580 |url=https://www.kfaero.ca/leasing/convair-580 |department=Leasing |access-date=August 28, 2020}}

;501-D13E: (Series I) Similar to the 501-D13 except for the location of the rear mount; certified on December 18, 1959.

;501-D13H: (Series I) Similar to the 501-D13D but with water-methanol injection; certified on February 20, 1964; used on the USAF's General Dynamics NC-131H Samaritan.{{cite web |website=Federation of American Scientists (FAS) |title=Test aircraft variants |url=https://fas.org/man/dod-101/sys/ac/list/n.htm |access-date=August 12, 2020}} and the Convair CV-580.

;501-D15: A {{cvt|4,050|shp}} engine under development{{when|date=May 2023}} for the Lockheed Electra.{{sfn|AIA Yearbook|1958|p=[https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1957-AIRCRAFT-YEAR-BOOK.pdf#page=122 121]}}

;501-D22: (Series II) Similar to the 501-D13A but with {{cvt|4,050|shp|kW|adj=pre|equivalent}} power rating at sea level takeoff, a shroud turbine, gearbox offset up, and no auto-feathering; certified on October 28, 1964. Used on the Lockheed L-100 Hercules.

;501-D22A: (Series III); Similar to the 501-D22 but with {{cvt|4,680|shp|kW|adj=pre|equivalent}} 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.

;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; powered the Aero Spacelines Super Guppy.{{sfn|Zigmunt|1997|p=[{{GBurl|7wI8SAq6l1cC|p=136}} 136]}}

;501-D22D: A {{cvt|4,591|shp}} derivative to power the proposed Lockheed L-400, a twin-engine version of the L-100.{{cite book |given=Chris |surname=Chant |title=Turboprop airliners |url=https://archive.org/stream/Turboprop/Aviones%20Turbopropulsados#page/n46 |year=1980 |page=45 |series=The illustrated aircraft guide |publisher=Macdonald Phoebus Ltd. |location=London |oclc=7485281}}

;501-D22E: Offered in 1979 as the initial engine for Lockheed's proposed L-100-60 (a stretched derivative of the Lockheed L-100).{{cite magazine |issn=0005-2175 |magazine=Aviation Week and Space Technology |title=Lockheed-Georgia developing stretched L-100 |url=https://archive.aviationweek.com/issue/19790827/#!&pid=95 |url-access=subscription |publication-date=August 27, 1979 |page=95 |department=Management}}

;501-D22G: (Series III) Similar to the 501-D22C but with {{cvt|4,815|shp|kW|adj=pre|equivalent}} power rating at sea level takeoff, a three-mount system, auto-feathering, and no water-methanol injection; certified on March 23, 1984. Used on the Convair CV-580

;501-D36: (Series II) Re-engined powerplant for the Royal Canadian Air Force (RCAF) CC-109 Cosmopolitan in 1966.{{cite book |title=Taming the skies: A celebration of Canadian flight |url={{GBurl|2fA3zXDdz4wC|p=157}} |publication-date=July 2003 |given=Peter |surname=Pigott |date=July 2003 |page=157 |publisher=Dundurn |oclc=52286158 |isbn=9781550024692}}

;501-D39: (Series IV) Offered for the Lockheed L-100 civil aircraft,{{cite conference |chapter=A new generation T56 turboprop engine |chapter-url=https://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1984/79474/V002T02A007/2395358/v002t02a007-84-gt-210.pdf |given=W.L. |surname=McIntire |title=Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery |conference=Turbo Expo: Power for Land, Sea, and Air |location=Amsterdam, Netherlands |volume=2: Aircraft engine; marine; microturbines and small turbomachinery |date=June 4–7, 1984 |doi=10.1115/84-GT-210 |oclc=4434363138 |isbn=978-0-7918-7947-4|doi-access=free}} starting in 1979 for the proposed L-100-60 as the successor engine to the 501-D22E, producing {{cvt|5,575|shp}} with {{cvt|14|ft|m|adj=mid|diameter}} propellers; was the commercial version of the 501-M71.{{cite journal |issn=0002-2667 |journal=Aircraft Engineering |title=The Hercules 130 Story |year=1979 |publication-date=August 1979 |pages=24–27 |volume=51 |number=8 |doi=10.1108/eb035551}}

;501-H2: Engine for the proposed Vanguard Model 30 lift fan aircraft that was entered in a 1961 vertical takeoff and landing (VTOL) transport competition; powered two {{cvt|8|ft|m|adj=mid|diameter}} fans within the wings and two {{cvt|14|ft|6|in|m|adj=mid|diameter}} propellers;{{cite conference |title=Thrust control of VTOL aircraft — part deux |url=https://ntrs.nasa.gov/api/citations/20140008647/downloads/20140008647.pdf |pages=1, [https://ntrs.nasa.gov/api/citations/20140008647/downloads/20140008647.pdf#page=12 12] |given=Daniel C. |surname=Dugan |date=January 22–24, 2014 |conference=AHS Aeromechanics Specialists' Conference |edition=Fifth Decennial |location=San Francisco, California, U.S.A. |publisher=National Aeronautics and Space Administration (NASA) |hdl=2060/20140008647 |oclc=908767485}} used a modified compressor for handling larger air flows.

;501-M1: Modified engine with new turbine blades that were hollow and air-cooled; on an experimental engine combining features of the 501-M1 with the 501-H2, ran at {{cvt|6,770|shp}} for nearly 2.5 hours at a turbine inlet temperature of {{cvt|2,060|F|C R K}} in January 1962 under a program funded by the Air Force and Navy.{{cite newsletter |work=AllisoNews |title=High horsepower attained by T56 |url=https://indianamemory.contentdm.oclc.org/digital/collection/AT/id/11297 |publication-date=January 19, 1962 |pages=1, [https://indianamemory.contentdm.oclc.org/digital/collection/AT/id/11299 3] |editor-first=Tom |editor-last=Joyce |volume=21 |number=15 |oclc=42343144}}

;501-M7B: Replaces the T56-A-7 on an experimental short takeoff and landing (STOL) version of the Lockheed C-130E (internally designated as the GL298-7) targeted in 1963 for the U.S. Army; power increased by 20% over the T56-A-7 due to lowering of the gear reduction ratio from 13.54 to 12.49, propeller blade changes to take advantage of the higher resulting propeller rotational speed, and a new turbine with air-cooled first and second-stage vanes and first-stage blades, so the turbine inlet temperature can be increased from {{cvt|1,780|F|C R K}} for the T56-A-7 to {{cvt|1,970|F|C R K}}; a {{cvt|4,591|shp|adj=mid}} rate engine that is restricted to {{cvt|4,200|shp}} and about {{cvt|10,600|lbf|kgf kN}} of static thrust on the STOL C-130E, but is capable of {{cvt|13,000|lbf|kgf kN}} thrust at full power and with a larger, {{cvt|15|ft|adj=mid}} propeller.{{cite magazine |issn=0005-2175 |magazine=Aviation Week and Space Technology |title=Power boost planned for STOL C-130 |url=https://archive.org/details/Aviation_Week_1963-01-07/page/n27 |department=Aeronautical engineering |publication-date=January 7, 1963 |given=David A. |surname=Anderton |location=Marietta, Georgia, U.S.A. |pages=54–55, 57}}

;501-M22: Internal designation for the T56-A-18;{{cite book |title=Quarterly indexes |series=Technical abstract bulletin |url={{GBurl|dxESAQAAMAAJ|pg=SL16-PA138}} |date=January–March 1969 |page=P–138 |publisher=((Defense Documentation Center: Defense Supply Agency)) }} submitted for FAA certification under a new type certificate.

;501-M23: Submitted for FAA certification under an amended type certificate.{{cite magazine |issn=0096-4913 |magazine=American Aviation |title=Certification workload grows: Greater use of delegation option foreseen for manufacturers of large, small aircraft |page=27 |publication-date=August 5, 1968}}

;501-M24: A demonstrator engine started in 1964{{harvnb|Sonnenburg|Schoneberger|1990|pp=[https://archive.org/details/allisonpowerofex0000sonn/page/196 196]–197|loc=Allison engine family tree}} that was later used to derive the 501-M62B engine developed for the XCH-62 helicopter.{{cite conference |issn=0148-7191 |title=Heavy lift helicopter main engines |date=October 16–18, 1973 |publication-date=February 1973 |given1=David R. |surname1=Woodley |given2=William S. |surname2=Castle |journal=SAE Technical Papers |series=SAE Technical Paper Series |volume=1 |publisher=Society of Automotive Engineers (SAE) |location=Los Angeles, California, U.S.A. |conference=National Aerospace Engineering and Manufacturing Meeting |doi=10.4271/730920}}

;501-M25: A {{cvt|6,000|shp}} four-stage fixed turbine engine similar to the T56-A-15, but with a {{cvt|90|F-change}} increase from the T56-A-15's maximum turbine inlet temperature rating of {{cvt|1970|F|C R K}}, and a variable geometry compressor for the inlet vane and the first five stator vanes; investigated in 1965 to power helicopters with a {{cvt|75,000|–|85,000|lb}} maximum takeoff weight (MTOW).{{cite report |author=Allison Division - General Motors |title=Powerplant studies for shaft-driven helicopter |url=https://archive.org/details/DTIC_AD0365464 |publication-date=July 1965 |oclc=872723329}}

;501-M26: A {{cvt|5,450|shp}} similar to the 501-M25 but with a free turbine instead of a fixed turbine, and a two-stage gas producer turbine; based on the T56-A-18 engine.{{cite report |title=Parametric analysis and preliminary design of a shaft-driven rotor system for a heavy lift helicopter |url=https://archive.org/details/DTIC_AD0640946/page/n45 |publication-date=August 1966 |page=15 |oclc=17309571 |vauthors=Bilezikjian V, Huss R, Brye J, Kaysing C, Childers H, Sachs I, Conway W, Varner C, Goldstein H, Wilson J, Hanson T}}

;501-M34: A {{cvt|5,175|shp}} turboshaft engine targeted for a 60-70 seat commuter helicopter proposal from Lockheed-California in 1966.{{cite magazine |issn=0005-2175 |magazine=Aviation Week and Space Technology |title=Lockheed studies commuter helicopter |url=https://archive.aviationweek.com/issue/19661205/#!&pid=39 |url-access=subscription |publication-date=December 5, 1966 |page=39}}

;501-M56: Engine candidate for the turboprop version of the Air Force A-X close air support aircraft, requiring {{cvt|4,400|shp}} of engine power.{{cite magazine |issn=0002-2349 |magazine=Air Force and Space Digest |publication-date=January 1970 |pages=33–36, 39 |title=AX: Lethal, accurate, agile, and cheap |url={{GBurl|w-U9AQAAIAAJ|pg=PA33}} |first=Edgar E. |last=Ulsamer}}

;501-M62B: An internal designation for the engine that became the {{convert|8,079|shp|adj=mid|abbr=off}} T701-AD-700 turboshaft, which weighed {{cvt|1,179|lb}} 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.{{cite journal |issn=0148-7191 |title=SAE Technical Paper Series: Advanced gas turbine for marine propulsion model 570-K |publication-date=February 1978 |given1=D.H. |surname1=Stinger |given2=W.A. |surname2=Redmond |journal=SAE Technical Papers |year=1978 |volume=1 |publisher=Society of Automotive Engineers (SAE) |doi=10.4271/780702}}

;501-M69: Engine proposed for transport-type offensive anti-air (TOAA) aircraft versions of the P-3 Orion (stretched derivative) and C-130 Hercules; rated power of {{cvt|4,678|shp}}, equivalent installed thrust-specific fuel consumption at cruise of {{cvt|0.52|tsfc}}.{{cite conference |issn=0096-736X |work=SAE Transactions |title=Land-based aircraft options for naval missions |given=William D. |surname=O'Neil |series=SAE Technical Paper Series |date=November 14, 1977 |volume=86 |number=4 |publisher=Society of Automotive Engineers (SAE) |pages=3316–3330 |location=Los Angeles, California, U.S.A. |doi=10.4271/770965 |jstor=44644625 |oclc=5817964451}}

;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.{{cite report |title=Survey of P-3C mission profiles for development of the T56-A-14 duty cycle |url=https://archive.org/details/DTIC_ADA130528 |given=S.M. |surname=Cote |publisher=Naval Air Systems Command (NAVAIR) |date=June 17, 1983 |oclc=38850276}}

;501-M71K: (Series IV) A {{cvt|5,250|hp}} engine using a larger propeller to power the Lockheed L-100-20 (L382E-44K-20) High Technology Test Bed (HTTB) for short takeoff and landing (STOL) starting in 1989,{{cite press release |author=Lockheed Aeronautical Systems |date=May 19, 1989 |title=Lockheed HTTB sets STOL records for time-to-climb, payload lift |publisher=PR Newswire |id={{Gale|A7275386}} |location=Palmdale, California, U.S.A.}} but was destroyed when the HTTB became airborne during a ground test on February 3, 1993.{{cite report |given=Preston E. |surname=Hicks |title=National Transportation Safety Board: Aviation accident final report (ATL93MA055) |url=https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20001211X11781&AKey=1&RType=HTML&IType=MA |publisher=National Transportation Safety Board |publication-date=March 18, 1994}}{{cite news |given=Stan |surname=Darden |title=Plane that crashed was simulating engine failure |url=https://www.upi.com/Archives/1993/02/04/Plane-that-crashed-was-simulating-engine-failure/4195728802000/ |agency=United Press International (UPI) |publication-date=February 4, 1993 |location=Marietta, Georgia, U.S.A.}}

;501-M78: A {{cvt|6000|shp|adj=mid}} demonstrator engine for NASA's Propfan Test Assessment (PTA) program. It had a modified reduction gearbox that reversed the direction of rotation and increased the output speed from 1,020 rpm to 1,698 rpm. The engine was attached to an eight-bladed, {{cvt|9|ft|m|adj=mid|diameter}}, single-rotation Hamilton Standard SR-7L propeller.{{cite magazine |issn=0459-6773 |magazine=Lockheed Horizons |title=PTA—Research at full scale |url=https://texashistory.unt.edu/ark:/67531/metapth1091896/m1/4/ |pages=2–11 |publication-date=December 1986 |number=22 |given=Dyckman T. |surname=Poland}} Shown as an {{cvt|8,000|hp}} engine at the 1983 Dayton Air Show,{{cite newsletter |work=Inside Indy Operations Newsletter |title=AGTO exhibit at air show |url=https://indianamemory.contentdm.oclc.org/digital/collection/AT/id/7723 |editor-first=John |editor-last=McCardle |publication-date=July 29, 1983 |volume=3 |number=15 |edition=Maywood |publisher=Detroit Diesel Allison}} the 501-M78 was flight-tested on a Gulfstream II aircraft beginning in May 1987.{{cite magazine |magazine=Flight International |url=https://www.flightglobal.com/FlightPDFArchive/1987/1987%20-%200338.PDF |title=Propfanned G2 takes to the air |given=Julian |surname=Moxon |location=Marietta, Georgia, USA |publication-date=May 9, 1987 |page=2 |department=World News |volume=131 |number=4061 |issn=0015-3710 |url-status=dead |archive-date=December 7, 2019 |archive-url=https://web.archive.org/web/20191207010604/https://www.flightglobal.com/FlightPDFArchive/1987/1987%20-%200338.PDF}} Various flight and ground testing programs were carried out on the engine testbed through June 1989.{{cite report |first=James F. |last=Unruh |title=Structure-borne noise estimates for the PTA aircraft |url=https://hdl.handle.net/2027/uiug.30112106730895?urlappend=%3Bseq=19%3Bownerid=35235383-18 |page=7 |publication-date=August 1990 |oclc=761332437 |series=NASA/CR-4315 |hdl=2027/uiug.30112106730895}}

;501-M80C: Also known as the T406-AD-400, a {{cvt|6,000|shp|kW|adj=mid|class}} turboshaft engine.{{cite report |author=Competition Advocate General, Department of the Navy |title=Long range acquisition estimates (FY 88 base year projections) |page=154 |url=https://hdl.handle.net/2027/uiug.30112104099186?urlappend=%3Bseq=185 |hdl=2027/uiug.30112104099186 |access-date=August 1, 2020}} 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.{{cite magazine |magazine=Flight International |url=https://www.flightglobal.com/FlightPDFArchive/1986/1986%20-%200210.PDF |title=Navy surprise on V-22 power |location=Detroit, Michigan, USA |publication-date=January 25, 1986 |page=16 |department=Propulsion |volume=129 |number=3995 |issn=0015-3710 |archive-url=https://web.archive.org/web/20140419014958/https://www.flightglobal.com/FlightPDFArchive/1986/1986%20-%200210.PDF |archive-date=April 19, 2014}}

;PW–Allison 501-M80E: A {{cvt|14,800|lbf|kgf kN|adj=mid|thrust}} contra-rotating geared propfan engine derived from the 501-M80C/T406 turboshaft engine and intended for use on a 92-seat version of the proposed MPC 75 regional aircraft; developed jointly with Pratt & Whitney.{{cite report |author=MBB CATIC Association |title=MPC 75 feasibility study - Summary report: B1 - Project definition |url=https://www.fzt.haw-hamburg.de/pers/Scholz/MPC75/MPC75_Feasibility_Study.pdf |date=July 1987 |pages=[https://www.fzt.haw-hamburg.de/pers/Scholz/MPC75/MPC75_Feasibility_Study.pdf#page=25 B1–23] to [https://www.fzt.haw-hamburg.de/pers/Scholz/MPC75/MPC75_Feasibility_Study.pdf#page=27 B1–25], [https://www.fzt.haw-hamburg.de/pers/Scholz/MPC75/MPC75_Feasibility_Study.pdf#page=32 B1–30], [https://www.fzt.haw-hamburg.de/pers/Scholz/MPC75/MPC75_Feasibility_Study.pdf#page=33 B1–31]}}

;501-M80R3: A turboprop engine offered as an equal partnership between Allison and Pratt & Whitney to power Lockheed's proposed successor to the P-3 Orion, which was developed for the U.S. Navy's long-range air antisubmarine warfare (ASW) capable aircraft (LRAACA) program.{{cite magazine |issn=0005-2175 |magazine=Aviation Week and Space Technology |title=Pratt, Allison team for P-3 follow-on engine candidate |url=https://archive.aviationweek.com/issue/19871221/#!&pid=32 |publication-date=December 21, 1987 |page=32 |department=Propulsion Technology |url-access=subscription |volume=127 |number=25}}

;501-M80R33: A propfan engine studied for the MPC 75{{cite conference |conference=Congress of the International Council of the Aeronautical Sciences |edition=17th |date=September 9–14, 1990 |location=Stockholm, Sweden |title=Aerodynamic design for a new regional aircraft |url=http://icas.org/ICAS_ARCHIVE/ICAS1990/ICAS-90-2.7.1.pdf |conference-url=http://icas.org/ICAS_ARCHIVE/ICAS1990/1990.php |pages=1251–1265 |surname=Greff |given=E. |oclc=1109530657}} that was based on the T406 core and rated at {{cvt|11,000|lbf|kgf kN|adj=mid|thrust}}.{{cite magazine |issn=0005-2175 |magazine=Aviation Week and Space Technology |title=Short Brothers to join Mpc-75 development team |url=https://archive.aviationweek.com/issue/19880516/#!&pid=67 |url-access=subscription |publication-date=May 16, 1988 |department=Air transport |pages=67, [https://archive.aviationweek.com/issue/19880516/#!&pid=69 69] |location=Hannover, West Germany}}

;501-KF: Allison's first marine gas turbine, it was used for electrical generation on Spruance-class destroyers, with each of the three turbogenerators producing 2,000 kW. A version with a new AC generator producing 2,500 kW was used on Kidd-class destroyers and Ticonderoga-class cruisers.{{Cite journal |last=Patterson |first=Jeffery |last2=Hoffman |first2=Donald |last3=Ochs |first3=Linda |date=1997 |title=ALLISON 501-K17 SSGTGS TECHNICAL DIRECTIVE EXPERIENCE |url=https://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78682/V001T02A001/2408912/v001t02a001-97-gt-169.pdf |journal=American Society of Mechanical Engineers}} A substantially altered and incompatible version was used on Arleigh Burke-class destroyers,{{Cite journal |last=Weisert |first=J. S. |date=1992 |title=A Summary of Allison Gas Turbine's Marine Experience |url=http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1992/78941/V002T03A011/2401629/v002t03a011-92-gt-327.pdf |journal=American Society of Mechanical Engineers |pages=3, 4}} generating 2,500 kW on Flight I and II ships{{Cite journal |last=Ewing |first=Donald |last2=Fortune |first2=Randall |last3=Rochon |first3=Brian |last4=Scott |first4=Robert |date=12 December 1989 |title=DDG 51 Flight III Design Development |journal=The Society of Naval Architects and Marine Engineers |pages=3-6}} and 3,000 kW on Flight IIA ships.{{Cite web |title=Reliable and Proven Power |url=https://www.rolls-royce.com/products-and-services/defence/naval/gas-turbines/ag9140-generator-set.aspx |access-date=2025-04-28 |website=rolls-royce.com}} Commercial variants have also been used on the Boeing 929 Jetfoil and Israeli Shimrit-class missile boats.

;570-KF: Part of a new series of engines introducing technology used in Allison's T701, introduced in 1983 and capable of producing {{cvt|6,350|shp|kW|adj=pre|}}. This engine has been used on Stockholm-class corvettes, Iroquois-class destroyers, and several private yachts.

;571-KF: Part of the same series as 570-KF, introduced in 1986. Largely identical to the 570-KF, but with an additional stage on the power turbine and higher compression ratio for greater power generation, at {{cvt|7,630|shp|kW|adj=pre|}}.{{Cite web |date=June 2000 |title=Rolls-Royce Allison 570/571/572-K |url=https://www.forecastinternational.com/archive/disp_old_pdf.cfm?ARC_ID=955 |website=Forecast International}}

;572-KF: Introduced in 1996, the 572-K series are further derivatives of 571-K incorporating an entirely new compressor along with three dry low emissions combustors taken directly from the Rolls-Royce RB211 to reduce the engine's emissions footprint. It is capable of generating between {{cvt|6,470|kW|shp|adj=pre|}} and {{cvt|7,830|kW|shp|adj=pre|}}

;MT5S: A replacement for the venerable 501-KF in military vessels, MT5S was developed for use aboard the Zumwalt-class destroyers as part of the RR4500 generator set,{{Cite journal |last1=Lahm |first1=Peter |last2=Halsey |first2=Jack |date=2014 |title=ABS NVR Type Approval of the Rolls-Royce Naval Marine Model MT5S Gas Turbine Engine and the RR4500 Generator Set |url=https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2014/45585/V01BT23A006/249294 |journal=American Society of Mechanical Engineers}} producing 3,800 kW. An uprated version known as MT5S-HE+ has since been developed for use in the AG6190 generator sets{{Cite web |date=2017 |title=Power surge - Increasing onboard electrical power for the US Navy's DDG-51 destroyers |url=https://www.rolls-royce.com/media/our-stories/discover/2017/power-surge-ag9160.aspx |website=Rolls Royce}} fitted to Flight III Arleigh Burke-class destroyers where it produces 4,000 kW.

File:Allison T56 mobile test unit MCAS Futenma 1982.JPEG, 1982]]

;T56-A-1: (Series I) A {{cvt|1,600|lb|kg|adj=mid|weight}} engine delivering {{cvt|3,460|shp}} and {{cvt|725|lbf|kgf kN}} residual jet thrust, which is equal to {{cvt|3,750|shp|kW|adj=pre|equivalent}}; single-shaft 14-stage axial flow compressor, cannular combustion chamber with 6-cylindrical through-flow combustion liners, 4-stage axial flow turbine; 13,800-rpm shaft connected to a 2-stage reduction gear with a 12.5-to-1 ratio, consisting of a 3.125-to-1 spur set followed by a 4.0-to-1 planet set.{{cite conference |issn=0148-7191 |title=The Allison T56 turbo-prop aircraft engine |date=April 18–21, 1955 |given1=John B. |surname1=Wheatley |given2=D.G. |surname2=Zimmerman |given3=R.W. |surname3=Hicks |journal=SAE Technical Papers |series=SAE Technical Paper Series |volume=1 |conference=SAE Golden Anniversary Aeronautical Meeting |location=New York City, New York, U.S.A. |publisher=SAE International |doi=10.4271/550075 |oclc=1109574510}}

;T56-A-1A: A {{cvt|3,750|shp|kW|adj=pre|equivalent}} engine used on the Lockheed C-130A Hercules.{{cite book |year=1961 |title=The 1961 aerospace year book |url=https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1961-AEROSPACE-YEAR-BOOK.pdf#page=405 |page=400 |edition=42nd |publisher=American Aviation Publications}}

;T56-A-2: Proposed gas generator engines for the McDonnell XHCH-1 helicopter.

;T56-A-3: A {{cvt|3250|shp|kW|adj=pre|equivalent}} 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.{{cite magazine |issn=0730-6784 |magazine=Air Force Magazine |title=What we've learned about turboprops |url={{GBurl|sioV46DL7AUC|p=82}} |pages=82, 85–86 |given=Brooke E. |surname=Allen |publication-date=March 1957 |volume=40 |number=3}}

;T56-A-4: A {{cvt|2,900|hp|kW|adj=mid}} engine for the C-131D executive transport/VC-131H VIP transport;{{cite magazine |issn=0886-2257 |magazine=Air & Space Magazine |title=The things it carried: How an unremarkable Convair C-131H transported cops, patients, prisoners, and Gerald Ford |url=https://www.airspacemag.com/history-of-flight/the-things-it-carried-45246668/?all |date=July 2008 |given=Thomas |surname=DeFrank}} 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 {{cvt|2100|shp}} 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.{{cite book |given=Bill |surname=Norton |title=STOL progenitors: The technology path to a large STOL aircraft and the C-17A |year=2002 |url={{GBurl|8zl09uULN8IC|p=42}} |pages=42–[{{GBurl|8zl09uULN8IC|p=43}} 43] |isbn=978-1-56347-576-4 |oclc=50447726 |publisher=American Institute of Aeronautics and Astronautics (AIAA) |doi=10.2514/4.868160}}

;T56-A-7: (Series II) A {{cvt|4,050|shp}} engine flight-tested on a U.S. Air Force Allison Boeing B-17 flying testbed aircraft, intended for the Lockheed C-130B;{{sfn|AIA Yearbook|1958|p=[https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1957-AIRCRAFT-YEAR-BOOK.pdf#page=122 121]}} also used on the C-130E; produces about {{cvt|9,500|lbf|kgf kN}} of static thrust.

;T56-A-7A: (Series II) Lockheed C-130B Hercules Starting May 1959.

;T56-A-7B: (Series II) Used on the U.S. Air Force C/HC/NC-130B, MC-130E, and WC-130F;{{cite report |given=Mark D. |surname=Wade |title=Aircraft/auxiliary power units/aerospace ground support equipment emission factors |url=https://archive.org/details/DTIC_ADA412045/page/n13 |page=6 |publication-date=October 2002 |publisher=United States Air Force IERA |oclc=834246721}} similar to -A-7A.

;T56-A-8: (Series II) Entered production in 1959; the original engine on the Grumman E-2C, using the Aeroproducts A6441FN-248 propeller.{{cite conference |chapter=T56 derivative engine in the improved E-2C |chapter-url=https://micronanomanufacturing.asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1985/79382/V001T01A003/4456523/v001t01a003-85-gt-176.pdf |given1=T.P. |surname1=Laughlin |given2=Joseph |surname2=Toth |title=Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery |conference=ASME 1985 International Gas Turbine Conference and Exhibit |location=Houston, Texas, U.S.A. |date=March 18–21, 1985 |doi=10.1115/85-GT-176 |oclc=7344649118 |isbn=978-0-7918-7938-2 |doi-access=free}}

;T56-A-9: (Series I) Used on the U.S. Air Force C/AC/DC/GC/NC/RC-130A and the C-130D.

;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 II) Water injection model that entered production in 1960.

;T56-A-10WA: (Series II) Used on the P-3A, EP-3A, and RP-3A.{{cite manual |title=T56 turboprop engine maintenance plan |url=https://archive.org/details/DTIC_ADA049939 |publication-date=January 1978 |author=ARINC Research Corp. |date=January 1978 |oclc=831768060}}

;T56-A-11: Ordered for 12 Royal Australian Air Force C-130s in 1958.{{cite newsletter |work=AllisoNews |title=Tech school C-130 program readied in Japan |url=https://indianamemory.contentdm.oclc.org/digital/collection/AT/id/4289 |publication-date=February 28, 1958 |pages=1, [https://indianamemory.contentdm.oclc.org/digital/collection/AT/id/4291 3] |editor-first=Tom |editor-last=Joyce |volume=17 |number=34 |oclc=42343144}}

;T56-A-13: (Series 3.5) Enhancements that improve SFC by 7.9%, increase maximum engine torque limit operation from {{cvt|32|to|48|C|F C R K|order=out}}, and increase turbine life; tested on a C-130H testbed aircraft in 2012.{{cite news |work=Defense Update |title=Enhanced T56 engine could save billions in C-130H operating costs |url=https://defense-update.com/20120919_c130_t56_35_engine_testing.html/t56-a-13s35 |date=September 19, 2012 |access-date=September 8, 2020}}

;T56-A-14: (Series III) Lockheed P-3/EP-3/WP-3/AP-3/CP-140 Aurora from August 1962; entered production in 1964.

;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) Upgrade of the T56-A-15 on the Air Force LC-130H.{{cite news |issn=1941-7217 |work=Design World |title=Raytheon given $573M contract for continued missile production |url=https://www.designworldonline.com/raytheon-given-573m-contract-for-continued-missile-production/ |given=Jake |surname=Meister |publication-date=March 21, 2016 |date=March 16, 2016}}

File:US Navy 081219-N-5142K-048 Bob Maiuvo works alongside Aviation Machinist Mate 2nd Class Tim Triest and Aviation Machinist Mate 2nd Class Marquette Beasley.jpg

;T56-A-16: (Series III) Used on the KC-130F, KC-130R, LC-130F, and LC-130R.{{R|"T56MaintPlan197801"|p=[https://archive.org/details/DTIC_ADA049939/page/n8 3]}}

;T56-A-16A: (Series 3.5).

;T56-A-18: A {{cvt|5,325|shp|kW|adj=pre|equivalent}}, {{cvt|1,554|lb}} variant that was designed and first run in 1965;{{cite newsletter |work=AllisoNews |title=New T56-A-18 runs successful five-hour test |url=https://indianamemory.contentdm.oclc.org/digital/collection/AT/id/11541 |publication-date=November 5, 1965 |editor-first=John J. |editor-last=McCardle |pages=1, [https://indianamemory.contentdm.oclc.org/digital/collection/AT/id/11543 3] |volume=25 |number=10 |oclc=42343144}} Navy-funded development with air-cooled blades and vanes in the first two stages; 50-hour preliminary flight rating test completed in 1968;{{cite book |year=1969 |title=The 1969 aerospace year book |url=https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1969-AEROSPACE-YEAR-BOOK.pdf#page=61 |page=52 |publisher=Aerospace Industries Association of America (AIA)}} turbine inlet temperature of {{cvt|2,070|F|C R K}}; 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);{{cite conference |chapter=Next generation turboprop gearboxes |chapter-url=https://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1982/79573/V002T02A013/2393964/v002t02a013-82-gt-236.pdf |given1=W.L. |surname1=McIntire |given2=D.A. |surname2=Wagner |title=Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery |conference=Turbo Expo: Power for Land, Sea, and Air |location=London, England, U.K. |volume=2: Aircraft engine; marine; microturbines and small turbomachinery |date=April 18–22, 1982 |doi=10.1115/82-GT-236 |oclc=8518954720 |isbn=978-0-7918-7957-3|doi-access=free}} used an eight-bladed Hamilton Standard variable-camber propeller.{{cite magazine |issn=0005-2175 |magazine=Aviation Week & Space Technology |title=Variable-camber propeller tested for Navy |url=https://archive.aviationweek.com/issue/19660530/#!&pid=101 |publication-date=May 30, 1966 |page=101}}

;T56-A-20: Proposed in 1968 to be funded within the 1969 fiscal year component improvement program (CIP).{{cite report |title=Department of Defense appropriations for 1969: Hearings before a subcommittee, ninetieth congress, second session |url=https://hdl.handle.net/2027/uva.x004234470?urlappend=%3Bseq=202%3Bownerid=27021597769555274-206 |page=198 |date=March 20, 1968 |hdl=2027/uva.x004234470}}

;T56-A-100: (Series IV) U.S. Air Force EMDP demonstrator

;T56-A-101: (Series IV) Offered for the Lockheed C-130 Hercules.

;T56-A-422: Used on U.S. Navy Northrop Grumman E-2C Hawkeye aircraft.{{cite web |website=Federation of American Scientists (FAS) |title=Electronic aircraft variants |url=https://fas.org/man/dod-101/sys/ac/list/e.htm |access-date=August 12, 2020}}

;T56-A-423: Used on U.S. Navy Lockheed EC-130G and EC-130Q aircraft.

;T56-A-425: (Series III) Replaced the T56-A-8 on the Grumman E-2C, using the {{cvt|13.5|ft|m|adj=mid|diameter}} Hamilton 54460-1 propeller; Grumman C-2A Greyhound from June 1974.

;T56-A-426: Used on the C-2A, E-2B, and TE-2A{{R|"T56MaintPlan197801"|p=[https://archive.org/details/DTIC_ADA049939/page/n8 3]}}

;T56-A-427: (Series IV) Northrop Grumman E-2 Hawkeye upgrades from 1972.

;T56-A-427A: (Series IV) Used on the Northrop Grumman E-2D Advanced Hawkeye (AHE), which first flew in 2007.{{cite news |work=AINonline |title=Advanced Hawkeye marches on |url=https://www.ainonline.com/aviation-news/defense/2019-04-11/advanced-hawkeye-marches |given=David |surname=Donald |date=April 11, 2019 |department=Defense |access-date=September 9, 2020}}

;T701-AD-700: An {{cvt|8,079|shp|adj=mid}} turboshaft powerplant developed from the 501-M62B and intended for use on the canceled three-engine Boeing Vertol XCH-62 heavy-lift helicopter;{{cite magazine |issn=0004-2560 |magazine=Army Research and Development |title=Army revises HLH program, sets competitive prototype tests |hdl=2027/osu.32435062846985 |url=https://hdl.handle.net/2027/osu.32435062846985?urlappend=%3Bseq=6 |pages=4–5 |department=R&D News |publication-date=March–April 1975 |volume=16 |number=2}} air flow of {{cvt|44|lb/s|kg/s}}, pressure ratio of 12.8:1, turbine temperature of {{cvt|2,290|F|C R K}}, and power/weight ratio of 6.85:1.{{cite conference |conference=AIAA/ASME/SAE/ASEE Joint Propulsion Conference |edition=24th |date=July 11–13, 1988 |chapter=Advanced turboprop and propfan development and testing |at=Figure 6. T701 standard day performance. |given1=T. F. |surname1=Gee |given2=A. S. |surname2=Novick |title=24th Joint Propulsion Conference |doi=10.2514/6.1988-3080}}

{{Portal|Aviation}}

{{Aircontent

|related=

• Allison T38
• Allison T40
• Allison T78
• Rolls-Royce AE 2100
• Rolls-Royce AE 3007
• Rolls-Royce T406

|similar engines=

• Bristol Proteus
• Ivchenko AI-20
• Lycoming T55
• Napier Eland
• Rolls-Royce Tyne

|lists=

• List of aircraft engines

|see also=

}}

{{Reflist}}

• {{cite book |ref={{SfnRef|AIA Yearbook|1958}} |author=Aircraft Industries Association, Inc. |title=1957-1958 aircraft year book |url=https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1957-AIRCRAFT-YEAR-BOOK.pdf |edition=39th |year=1958 |publisher=American Aviation Publications, Inc. |access-date=2020-12-08 |archive-date=2022-01-22 |archive-url=https://web.archive.org/web/20220122005549/http://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1957-AIRCRAFT-YEAR-BOOK.pdf |url-status=dead}}
• {{cite web |ref={{SfnRef|Allison Industrial Gas Turbines|1983}} |website=International Power Technology |author=Allison Gas Turbine Operations |title=Allison industrial gas turbines 501-K, 570-K |url=http://intpower.com/wp-content/uploads/1986/10/501-brochure.pdf |date=August 1983 |access-date=August 7, 2020}}
• {{cite magazine |issn=0005-2175 |magazine=Aviation Week |title=Allison moves to boost its airline sales |url=https://archive.org/details/Aviation_Week_1955-12-12/page/n13 |pages=27, 29–31 |publication-date=December 12, 1955 |given=Robert |surname=Hotz |location=Indianapolis, Indiana, U.S.A. |department=Management |volume=63 |number=24}}
• {{cite book |given1=Paul |surname1=Sonnenburg |given2=William A |surname2=Schoneberger |title=Allison power of excellence 1915-1990 |url=https://archive.org/details/allisonpowerofex0000sonn |year=1990 |publisher=Coastline Publishers |url-access=limited |isbn=0-9627074-0-6 |oclc=22964244}}
• {{cite magazine |issn=0005-2175 |magazine=Aviation Week & Space Technology |title=New family of Allison engines evolving |url=https://archive.aviationweek.com/issue/19740812/#!&pid=44 |pages=44(4) |publication-date=August 12, 1974 |given=Michael L. |surname=Yaffee |department=Aeronautical engineering |url-access=subscription}}
• {{cite book |title=Allison, the people and the power: A pictorial history |url={{GBurl|7wI8SAq6l1cC}} |given=Joan Everling |surname=Zigmunt |date=June 1997 |publisher=Turner Publishing Company |isbn=1-56311-315-5 |oclc=37537128}}

• [http://www.rolls-royce.com/defence/products/tactical_aircraft/t56/index.jsp# T56 page at Rolls-Royce website]

{{Allison aeroengines}}

{{Rolls-Royce plc aeroengines}}

{{USAF gas turbine engines}}

T56

Category:1950s turboprop engines