Allison T56


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.

Design and development

The T56 turboprop, evolved from Allison's previous T38 series, was first flown in the nose of a B-17 test-bed aircraft in 1954. 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. 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.
A major setback occurred when a T56-A-1 engine delivered to Lockheed in May, 1953, produced only, not the required needed for the YC-130A. 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 rating with a pressure ratio of 9.25:1 while the T56-A-427 fitted to the E-2 Hawkeye has a rating and a 12:1 pressure ratio. In addition, the T56 produces approximately residual thrust from its exhaust.
A marinised turboshaft version, the 501K engine, is used to generate electrical power onboard all the U.S. Navy's cruisers and almost all of its destroyers.
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.
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 to control the engines and propellers. It drives new six-bladed scimitar propellers from Dowty Rotol.

Variants

;501-D12:
;501-D13: Lockheed L-188 Electra and Convair CV-580 starting December 1957
;501-D13A: Similar to -D13
;501-D13D: Similar to -D13
;501-D13H: Similar to -D13
;501-D15:
;501-D22: Lockheed L-100 Hercules
;501-D36A:
;501-D22A:
;501-D22C: similar to -D22A
;501-D22G: similar to -D22A
;501-M62:Company designation for the T701-AD-700 turboshaft engine to power the Boeing Vertol XCH-62 Heavy-lift helicopter
;501-M78: A, demonstrator engine for NASA's Propfan Test Assessment program; flight-tested on a Gulfstream II aircraft
;501-M80C: Turboshaft engine for the V-22 Osprey tiltrotor assault transport
;XT56-A-1:
;XT56-A-2: proposed gas generator engines for the McDonnell XHCH-1
;T56-A-3:
;XT56-A-4: proposed engines for the McDonnell XHRH-1, with propeller drive and gas generator bleed for rotor-tip pressure jets.
;YT56: Gas generator engines for the C-130B BLC demonstrator.
;T56-A-5: turboshaft version for the Piasecki YH-16B Transporter helicopter.
;T56-A-7:
;T56-A-8:
;T56-A-9:
;T56-A-9D: Lockheed C-130A Hercules Starting December 1956 and on all Grumman E-2A Hawkeyes from 1960
;T56-A-9E: Similar to -A-9D
;T56-A-10W: with water injection
;T56-A-7A: Lockheed C-130B Hercules Starting May 1959
;T56-A-7B: Similar to -A-7A
;T56-A-10WA:
;T56-A-14: Lockheed P-3/EP-3/WP-3/AP-3/CP-140 Aurora from August 1962
;T56-A-15: Lockheed C-130H Hercules USAF from June 1974
;T56-A-16: Lockheed C-130H/R/T Hercules USN/USMC
;T56-A-425: Grumman C-2A Greyhound from June 1974
;T56-A-14A: Fuel efficiency and reliability upgrade, Lockheed WP-3D Orion from May 2015.
;T56-A-15A:
;T56-A-16A:
;T56-A-427: Northrop Grumman E-2 Hawkeye upgrades from 1972
;T56-A-427A: Northrop Grumman E-2D Advanced Hawkeye
;T701-AD-700: Turboshaft engine for the Boeing Vertol XCH-62 heavy-lift helicopter.

Applications