Allison T56

  (Redirected from Allison 501)

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
Allison T56 turboprop for C-130 2007.JPEG
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

Design and developmentEdit

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

The T56 turboprop, evolved from Allison's previous T38 series,[5] was first flown in the nose of a B-17 test-bed aircraft in 1954.[5] 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.[6] Originally fitted to the Lockheed C-130 Hercules, the T56 was also installed on the P-3 and E-2/C-2 aircraft, as well as civilian airliners such as the Lockheed Electra and Convair 580.[5]

A major setback occurred when a T56-A-1 engine delivered to Lockheed in May, 1953, produced only 3,000 hp, not the required 3,750 shp needed for the C-130. A further setback occurred in August 1953 when an engine being tested failed after only 6 ½ hours run time. A redesign of the engine failed during testing in September of the same year. A second redesign was more successful. 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 4591 shp rating with a compression ratio of 9.25:1 while the T56-A-427 fitted to the E-2 Hawkeye has a 5250 shp rating and a 12:1 compression. In addition, the T56 produces approximately 750 lbs of thrust from its exhaust.[7]

A marinised turboshaft version, the 501K engine, is used to generate electrical power for all U.S. Navy cruisers and destroyers currently in commission.[4]

An engine enhancement program to reduce fuel consumption and decrease temperatures was approved in 2013, and the US Air Force expects to save $2 billion and extend the C-130 fleet life.[8]

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.[9] It drives new six-bladed scimitar propellers from Dowty Rotol.


(Series I) Lockheed L-188 Electra and Convair CV-580 (Replacing P&W R-2800) starting December 1957
(Series I) Similar to -D13
(Series I) Similar to -D13
(Series I) Similar to -D13
(Series II) Lockheed L-100 Hercules
(Series II) (non-type certified)
(Series III)
(Series III) similar to -D22A
(Series III) similar to -D22A
Company designation for the T701-AD-700 turboshaft engine to power the Boeing Vertol XCH-62 Heavy-lift helicopter
A 6,000 shaft horsepower (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[10]
Turboshaft engine for the V-22 Osprey tiltrotor assault transport[11]
A T56 on a mobile test unit at MCAS Futenma, 1982
Maintenance of a T56-A-16, 2009
proposed gas generator engines for the McDonnell XHCH-1
3,250 shp (2,420 kW)
proposed engines for the McDonnell XHRH-1, with propeller drive and gas generator bleed for rotor-tip pressure jets.
Gas generator engines for the C-130B BLC demonstrator.[12]
2,100 shp (1,600 kW) turboshaft version for the Piasecki YH-16B Transporter helicopter.
(Series I)
(Series I)
(Series I)
(Series I) Lockheed C-130A Hercules Starting December 1956 and on all Grumman E-2A Hawkeyes from 1960
(Series I) Similar to -A-9D
(Series I) with water injection
(Series II) Lockheed C-130B Hercules Starting May 1959
(Series II) Similar to -A-7A
(Series II)
(Series III) Lockheed P-3/EP-3/WP-3/AP-3/CP-140 Aurora from August 1962
(Series III) Lockheed C-130H Hercules USAF from June 1974
(Series III) Lockheed C-130H/R/T Hercules USN/USMC
(Series III) Grumman C-2A Greyhound from June 1974
(Series 3.5) Fuel efficiency and reliability upgrade, Lockheed WP-3D Orion from May 2015.
(Series 3.5)
(Series 3.5)
(Series IV) Northrop Grumman E-2 Hawkeye upgrades from 1972
(Series IV) Northrop Grumman E-2D Advanced Hawkeye
(501-M62) Turboshaft engine for the Boeing Vertol XCH-62 heavy-lift helicopter.


Specifications (T56 Series IV)Edit

Data from Rolls-Royce.[13]

General characteristics



  • Maximum power output: 4,350 shp (3,240 kW) limited to 4,100 shp (3,100 kW)
  • Turbine inlet temperature: 860 °C (1,580 °F)
  • Fuel consumption: 2,412 lb/h (1,094 kg/h)
  • Power-to-weight ratio: 2.75 shp/lb (4.52 kW/kg)

See alsoEdit

Related development

Comparable engines

Related lists


  1. ^ "Aurora".Retrieved April 2019
  2. ^ "Rolls-Royce".Retrieved November 2018
  3. ^ Global Security T56
  4. ^ a b "Rolls Royce T56 Product Sheet" (PDF). Archived from the original (PDF) on 2013-02-07. Retrieved 2012-11-02. Retrieved on 1 November 2012.
  5. ^ a b c "Global Security".Retrieved on 1 November 2012.
  6. ^
  7. ^ "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. Retrieved on 2 November 2013
  8. ^ "NOAA 'Hurricane Hunters' First To Get T56 Series 3.5 Engine Enhancement" Aero News, November 14, 2013. Accessed: December 1, 2013.
  9. ^ "Rolls Royce AE-2100 Product Sheet" (PDF). Archived from the original (PDF) on 2013-02-17. Retrieved 2012-11-02. Retrieved on 1 November 2012.
  10. ^ 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.
  11. ^ "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.
  12. ^ "Le Bourget Marathon". Flight. 79 (2726): 784–792. 8 June 1961. Retrieved 14 November 2018.
  13. ^ Rolls, Royce . Training Manual . T56/501D Series III. Rolls-Royce, 2003. 8-1 To 8-24. Print.

External linksEdit