Allison T56 variants

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

Allison T56 variants
Allison T-56 on display at the National Naval Aviation Museum, Pensacola
Type Turboprop/turboshaft
National origin United States
Manufacturer Allison Engine Company
Rolls-Royce Holdings
First run 1950
Main article: Allison T56

Initial civil variants (Series I) were designed and produced by the Allison Engine Company as the 501-D and powered the Lockheed C-130 Hercules. Later variants (Series II,III, 3,5 and IV) gave increased performance through design refinements.

Further derivatives of the 501-D/T56 were produced as turboshafts for helicopters including a variant designated T701 that was developed for the canceled Boeing Vertol XCH-62 project.

Commercial variants (501-D)
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.[1]
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 721 ft/s (220 m/s; 427 kn; 492 mph; 791 km/h) for the 13 ft 6 in (4.11 m) Aeroproducts 606 propeller; 3,750 equivalent shp (2,800 kW) power rating at sea level takeoff, 14-stage axial compressor, 6 cannular combustion chambers, and 4-stage turbine; 13,820 rpm shaft and 1,780 °F (970 °C; 2,240 °R; 1,240 K) turbine inlet temperature;[2] certified on September 12, 1957.[3]
501-D13A
(Series I) Similar to the 501-D13 but using a Hamilton Standard propeller; certified on April 15, 1958.[3]
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;[3] used on the Convair CV-580 passenger aircraft.[4]
501-D13E
(Series I) Similar to the 501-D13 except for the location of the rear mount; certified on December 18, 1959.[3]
501-D13H
(Series I) Similar to the 501-D13D but with water-methanol injection; certified on February 20, 1964;[3] used on the USAF's General Dynamics NC-131H Samaritan.[5] and the Convair CV-580.[4]
501-D15
A 4,050 shp (3,020 kW) engine under development for the Lockheed Electra.[6]
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.[3] Used on the 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.[3]
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;[3] powered the Aero Spacelines Super Guppy.[7]
501-D22D
A 4,591 shp (3,424 kW) derivative to power the proposed Lockheed L-400, a twin-engine version of the L-100.[8]
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.[3] Used on the Convair CV-580[4]
501-D36
(Series II) Re-engined powerplant for the Royal Canadian Air Force (RCAF) CC-109 Cosmopolitan in 1966.[9]
501-D39
(Series IV) Offered for the Lockheed L-100 civil aircraft.[10]
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 8 ft diameter (2.4 m) fans within the wings and two 14 ft 6 in diameter (4.42 m) propellers.[11]
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 1,780 °F (970 °C; 2,240 °R; 1,240 K) for the T56-A-7 to 1,970 °F (1,080 °C; 2,430 °R; 1,350 K); a 4,591 shp (3,424 kW) rate engine that is restricted to 4,200 shp (3,100 kW) and about 10,600 lbf (4,800 kgf; 47 kN) of static thrust on the STOL C-130E, but is capable of 13,000 lbf (5,900 kgf; 58 kN) thrust at full power and with a larger, 15 ft (4.6 m) propeller.[12]
501-M24
A demonstrator engine later used to derive the 501-M62B engine developed for the XCH-62 helicopter.[13]
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).[14]
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.[14]
501-M34
A 5,175 shp (3,859 kW) turboshaft engine targeted for a 60-70 seat commuter helicopter proposal from Lockheed-California in 1966.[15]
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.[16]
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 4,678 shp (3,488 kW), equivalent installed thrust-specific fuel consumption at cruise of 0.52 lb/(lbf⋅h) (15 g/(kN⋅s)).[17]
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.[18]
501-M71K
(Series IV) A 5,250 hp (3,910 kW) 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,[19] but was destroyed in a fatal crash on February 3, 1993.[20]
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.[21]
501-M80C
Also known as the T406-AD-400, a 6,000 shp class (4,500 kW) turboshaft engine.[22] 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.[23]
PW–Allison 501-M80E
A 14,800 lbf thrust (6,700 kgf; 66 kN) 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.[24]
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.[25]
501-M80R33
A propfan engine studied for the MPC 75[26] that was based on the T406 core and rated at 11,000 lbf thrust (5,000 kgf; 49 kN).[27]

Military variants (T56)
A T56 on a mobile test unit at MCAS Futenma, 1982
T56-A-1
(Series I) A 1,600 lb weight (730 kg) engine delivering 3,460 shp (2,580 kW) and 725 lbf (329 kgf; 3.22 kN) residual jet thrust, which is equal to 3,750 equivalent shp (2,800 kW); 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.[28]
T56-A-1A
A 3,750 equivalent shp (2,800 kW) engine used on the Lockheed C-130A Hercules.[29]
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.[30]
T56-A-4
A 2,900 hp (2,200 kW) engine for the C-131D executive transport/VC-131H VIP transport;[31] 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.[32]
T56-A-7
(Series II) 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;[6] also used on the C-130E; produces about 9,500 lbf (4,300 kgf; 42 kN) of static thrust.[12]
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;[33] similar to -A-7A.
T56-A-8
(Series II) Entered production in 1959;[18] the original engine on the Grumman E-2C, using the Aeroproducts A6441FN-248 propeller.[34]
T56-A-9
(Series I) Used on the U.S. Air Force C/AC/DC/NC/RC-130A and the C-130D.[33]
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.[18]
T56-A-10WA
(Series II) Used on the P-3A, EP-3A, and RP-3A.[35]
T56-A-13
(Series 3.5) Enhancements that improve SFC by 7.9%, increase maximum engine torque limit operation from 90 to 118 °F (32 to 48 °C; 549 to 578 °R; 305 to 321 K), and increase turbine life; tested on a C-130H testbed aircraft in 2012.[36]
T56-A-14
(Series III) Lockheed P-3/EP-3/WP-3/AP-3/CP-140 Aurora from August 1962; entered production in 1964.[18]
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.[37]
Maintenance of a T56-A-16, 2009
T56-A-16
(Series III) Used on the KC-130F, KC-130R, LC-130F, and LC-130R.[35]:3
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;[38] 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)[39]
T56-A-100
(Series IV) U.S. Air Force EMDP demonstrator[10]
T56-A-101
(Series IV) Offered for the Lockheed C-130 Hercules.[10]
T56-A-422
Used on U.S. Navy Northrop Grumman E-2C Hawkeye aircraft.[40]
T56-A-423
Used on U.S. Navy Lockheed EC-130G and EC-130Q aircraft.[40]
T56-A-425
(Series III) Replaced the T56-A-8 on the Grumman E-2C, using the 13.5 ft diameter (4.1 m) Hamilton 54460-1 propeller;[34] Grumman C-2A Greyhound from June 1974.
T56-A-426
Used on the C-2A, E-2B, and TE-2A[35]: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.[41]

T701
T701-AD-700
An 8,079 shp (6,025 kW) turboshaft powerplant developed from the 501-M62B and intended for use on the canceled three-engine Boeing Vertol XCH-62 heavy-lift helicopter.[42]

See also

Related development

Comparable engines

Related lists

References
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Bibliography
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