page_title: Allison T56
section_title: Military variants
hierarchical_section_title: Allison T56 / Variants / Military variants
caption_attribution_description: English: WILLOW GROVE, Pa. (Dec. 19, 2008) Bob Maiuvo, a WG-10 civilian aircraft mechanic, works alongside Aviation Machinist Mate 2nd Class Tim Triest and Aviation Machinist Mate 2nd Class Marquette Beasley from NAS JRB Willow Grove's Aircraft Intermediate Maintenance Department to inspect a T56-A-16 turbo prop engine from a C-130 aircraft. (U.S. Navy photo by Mass Communication Specialist 1st Class Robert Keilman/Released)
context_page_description: 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 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.
context_section_description: T56-A-1
  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
  T56-A-1A
  A 3,750 equivalent shp (2,800 kW) engine used on the Lockheed C-130A Hercules
  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
  T56-A-4
  A 2,900 hp (2,200 kW) engine for the C-131D executive transport/VC-131H VIP transport; 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
  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
  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; the original engine on the Grumman E-2C, using the Aeroproducts A6441FN-248 propeller
  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
  T56-A-10WA
  (Series II) Used on the P-3A, EP-3A, and RP-3A
  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
  T56-A-16
  (Series III) Used on the KC-130F, KC-130R, LC-130F, and LC-130R
  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; 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)
  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
  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 13.5 ft diameter (4.1 m) Hamilton 54460-1 propeller; Grumman C-2A Greyhound from June 1974
  T56-A-426
  Used on the C-2A, E-2B, and TE-2A
  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
caption: Maintenance of a T56-A-16, 2009
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