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]
The T56-A-1 delivered to Lockheed in May, 1953, produced only 3,000shp (2,237kW), compared to the required 3,750shp (2,796kW) for the YC-130A. 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 4,591shp (3,424kW) rating with a pressure ratio of 9.25:1 while the T56-A-427 fitted to the E-2 Hawkeye has a 5,250shp (3,915kW) rating and a 12:1 pressure ratio. In addition, the T56 produces approximately 750lbf (3,336.17N) residual thrust from its exhaust.[6]
Over the years, there have been a number of engine development versions, which are grouped by series numbers. The Series I collection of derivatives came out in 1954, producing a sea-level static power rating of 3,460 propeller shp (2,580kW) at a 59°F (15°C; 519°R; 288K) ambient temperature. Successive engine follow-ups included the Series II, which was introduced in 1958 and had an increased power rating of 3,755 prop shp (2,800kW), and the Series III, which came out in 1964 and had another power increase to 4,591 prop shp (3,424kW). The Series II and III derivatives were developed under military component improvement programs (CIP).[7] By 1965, Allison was proposing the development of Series IV derivatives,[8] but in 1968, the United States Congress restricted CIP work to reliability and maintainability improvements instead of performance improvements.[7] The Series IV derivatives were finally developed in the 1980s after being approved for a U.S. Air Force engine model derivative program (EMDP) in the 1979 fiscal year budget. Series IV engines include the Air Force EMDP T56-A-100 demonstrator, model T56-A-101 for the Air Force's C-130 aircraft, T56-A-427 for NAVAIR's E-2C and C-2A aircraft, 501-D39 for the Lockheed L-100 aircraft, and the 501-K34 marine turboshaft for NAVSEA. The T56-A-427 was capable of 5,912 prop shp (4,409kW), but it was torque-limited to 5,250 prop shp (3,910kW).[9]
The T56 Series 3.5, an engine enhancement program to reduce fuel consumption and decrease temperatures, was approved in 2013 for the National Oceanic and Atmospheric Administration (NOAA) WP-3D "Hurricane Hunter" aircraft.[12] After eight years of development and marketing efforts by Rolls-Royce, the T56 Series 3.5 was also approved in 2015 for engine retrofits on the U.S. Air Force's legacy C-130 aircraft that were currently in service with T56 Series 3 engines.[13] Propeller upgrades to eight-bladed NP2000 propellers from UTC Aerospace Systems have been applied to the E-2 Hawkeye, C-2 Greyhound, and older-model C-130 Hercules aircraft,[14] and will be adopted on the P-3 Orion.[15]
Production of the T56 engine is expected to continue to at least 2026, with the U.S. Naval Air Systems Command (NAVAIR) order in 2019 of 24 additional E-2D Advanced Hawkeyes (AHEs) powered by the T56-A-427A engine variant.[16]
Experimental and non-turboprop uses
The T56/Model 501 engine has been used in a number of experimental efforts, and as something other than a turboprop powerplant. In early 1960, two Allison YT56-A-6 experimental turbine engines without propellers were added next to existing propulsion engines on flight tests of a Lockheed NC-130B 58-0712 aircraft. The YT56-A-6 produced pressurized air for blowing over control surfaces to demonstrate boundary layer control (BLC), which helped to enable short takeoff and landing (STOL) performance.[17]:42–44 In 1963, Lockheed and Allison designed another STOL demonstrator, this time for a U.S. Army requirement. Lockheed internal designation GL298-7 involved a C-130E Hercules that was re-engined with 4,591shp (3,424kW) 501-M7B turboprops. The 501-M7B produced more power than the normally installed, 3,755shp (2,800kW) T56-A-7 engines by about 20% (though the 501-M7B was limited to 4,200shp (3,100kW) to avoid additional structural changes), because the introduction of air cooling in the turbine's first-stage blade and the first and second-stage vanes allowed for an increase in the turbine inlet temperature.[18]
In 1963, an aeroderivative line of industrial gas turbines based on the T56 was introduced in under the 501-K name.[19] The 501-K is offered as a single-shaft version for constant speed applications and as a two-shaft version for variable-speed, high-torque applications.[20] Series II standard turbines included the natural gas-fueled 501-K5 and the liquid-fueled 501-K14. The air-cooled Series III turbines included the natural gas-fueled 501-K13 and the liquid-fueled 501-K15.[21] A marinized turboshaft version of the 501-K is used to generate electrical power onboard all the U.S. Navy's cruisers (Ticonderogaclass) and almost all of its destroyers (Arleigh Burkeclass).
During the late 1960s, the U.S. Navy funded the development of the T56-A-18 engine, which introduced a new gearbox compared with the early gearbox on the T56-A-7.[22] The 50-hour preliminary flight rating test (PFRT) was completed for the T56-A-18 in 1968.[23] In the early 1970s, Boeing Vertol selected Allison (at that time known as the Detroit Diesel Allison Division (DDAD) of General Motors) to power a dynamic-system test rig (DSTR) supporting the development of its XCH-62 heavy-lift helicopter (HLH) program for the U.S. Army, using the Allison 501-M62B turboshaft engine.[24] The 501-M62B had a 13-stage compressor based on the 501-M24 demonstrator engine, which was a fixed single-shaft engine with an increased overall pressure ratio and a variable-geometry compressor, and it had an annular combustor based on the T56-A-18 and other development programs. The turbine was derived from the fixed single-shaft T56, which had a four-stage section in which the first two stages provided enough power to drive the compressor, and the other two stages offered enough power to drive the propeller shaft. For the double-shaft 501-M62B engine, it was split into a two-stage turbine driving the compressor, where the turbine stages had air-cooled blades and vanes, and a two-stage free power turbine driving the propeller through a gearbox. The 501-M62B also incorporated improvements proven by Allison's GMA 300 demonstrator program, which allowed for an airflow of 42lb/s (1,100kg/min).[25] After DSTR testing was successful, the 501-M62B engine was further developed into the XT701-AD-700 engine for use on the HLH. The 8,079shp (6,025kW) XT701 passed the tests required to enter ground and flight testing on the HLH,[26] but funding of the HLH program was canceled in August 1975, when the triple-turbine, tandem-rotor helicopter prototype had reached 95% completion.[27]:3
Following the HLH program cancellation, Allison decided in early 1976 to apply the XT701 engine technology into a new industrial gas turbine product, the 570-K. The industrial engine, which entered production in the late 1970s, was derated to 7,170shp (5,350kW) and adapted for marine, gas compressor, and electrical power generation variants.[26] The only major changes made for the 570-K were the elimination of compressor bleed air and replacing the XT701's titanium compressor case with a steel case. The 570-K was then adapted to the 6,000shp (4,500kW) 501-M78B demonstration engine, which Lockheed flew on a Grumman Gulfstream II as part of the NASA Propfan Test Assessment Program in the late 1980s. The 501-M78B had the same 13-stage compressor, combustor, 2-stage gas producer turbine, and 2-stage free power turbine used on the XT701 and 570-K, but it was connected through a 6.797 reduction ratio gearbox to a 9ft diameter (2.7m)Hamilton Standard single-rotation propfan, containing propfan blades that were swept back 45 degrees at the tips.[28]
The T56 has been developed extensively throughout its production run, the many variants are described by the manufacturer as belonging to four main series groups.
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.
Maximum power output:SLS, 59°F (15°C), max power: 5,912shp (4,409kW) (torque limited to 5,250shp (3,910kW)); 25,000ft altitude (7,600m), Mach 0.5, max continuous power: 3,180shp (2,370kW)[9]
A turboprop engine is a turbine engine that drives an aircraft propeller.
The Bristol Proteus was the Bristol Engine Company's first mass-produced gas turbine engine design, a turboprop that delivered just over 4,000 hp (3,000 kW). The Proteus was a reverse-flow gas turbine. Because the second turbine drove no compressor stages, but only the propeller, this engine was classified as a free-turbine. It powered the Bristol Britannia airliner, small naval patrol craft, hovercraft and electrical generating sets. It was also used to power a land-speed record car, the Bluebird-Proteus CN7. After the merger of Bristol with Armstrong Siddeley the engine became the Bristol Siddeley Proteus, and later the Rolls-Royce Proteus. The Proteus was to have been superseded by the Bristol Orion which would have given a Britannia a 75% increase in power for cruising faster.
The Pratt & Whitney Canada PT6 is a turboprop aircraft engine produced by Pratt & Whitney Canada. Its design was started in 1958, it first ran in February 1960, first flew on 30 May 1961, entered service in 1964 and has been continuously updated since. It consists of two basic sections: a gas generator with accessory gearbox and a free power turbine with reduction gearbox, and is often seemingly mounted backwards in an aircraft in so far as the intake is at the rear and the exhaust at the front. Many variants of the PT6 have been produced, not only as turboprops but also as turboshaft engines for helicopters, land vehicles, hovercraft, and boats; as auxiliary power units; and for industrial uses. By November 2015, 51,000 had been produced, had logged 400 million flight hours from 1963 to 2016. It is known for its reliability with an in-flight shutdown rate of 1 per 651,126 hours in 2016. The PT6A covers the power range between 580 and 1,940 shp while the PT6B/C are turboshaft variants for helicopters.
The Rolls-Royce T406 is a turboshaft engine that powers the Bell Boeing V-22 Osprey tiltrotor. The engine delivers 6,000 shp (4,470 kW).
The Europrop International TP400-D6 is an 11,000 shp (8,200 kW) powerplant, developed and produced by Europrop International for the Airbus A400M Atlas military transport aircraft. The TP400 is the most powerful single-rotation turboprop in service; only the contra-rotating Kuznetsov NK-12 is larger.
The Rolls-Royce AE 2100 is a turboprop developed by Allison Engine Company, now part of Rolls-Royce North America. The engine was originally known as the GMA 2100, when Allison was a division of former corporate parent General Motors.
The Pratt & Whitney Canada PW100 aircraft engine family is a series of 1,800 to 5,000 shaft horsepower turboprops manufactured by Pratt & Whitney Canada. Pratt & Whitney Canada dominates the turboprops market with 89% of the turboprop regional airliner installed base in 2016, leading GE Aviation and Allison Engine Company.
The Rolls-Royce RB.109 Tyne is a twin-shaft turboprop engine developed in the mid to late 1950s by Rolls-Royce Limited to a requirement for the Vickers Vanguard airliner. It was first test flown during 1956 in the nose of a modified Avro Lincoln. Following company naming convention for gas turbine engines this turboprop design was named after the River Tyne.
The Rolls-Royce Gnome is a British turboshaft engine originally developed by the de Havilland Engine Company as a licence-built General Electric T58, an American mid-1950s design. The Gnome came to Rolls-Royce after their takeover of Bristol Siddeley in 1968, Bristol having absorbed de Havilland Engines Limited in 1961.
The Rolls-Royce Gem is a turboshaft engine developed specifically for the Westland Lynx helicopter in the 1970s. The design started off at de Havilland and was passed to Bristol Siddeley as the BS.360. When Rolls-Royce bought out the latter in 1966, it became the RS.360.
The General Electric GE38 is a gas turbine developed by GE Aviation for turboprop and turboshaft applications. It powers the Sikorsky CH-53K King Stallion as the T408.
The Turbomeca Astazou is a highly successful series of turboprop and turboshaft engines, first run in 1957. The original version weighed 110 kg (243 lb) and developed 240 kW (320 shp) at 40,000 rpm. It was admitted for aviation service on May 29, 1961, after a 150-hour test run. The main developing engineer was G. Sporer. It was named after two summits of the Pyrenees.
The Allison T40, company designation Allison Model 500, was an early American turboprop engine composed of two Allison T38 power sections driving a contra-rotating propeller via a common gearbox.
The General Electric T64 is a free-turbine turboshaft engine that was originally developed for use on helicopters, but which was later used on fixed-wing aircraft as well. General Electric introduced the engine in 1964. The original engine design included technical innovations such as corrosion resistant and high-temperature coatings. The engine features a high overall pressure ratio, yielding a low specific fuel consumption for its time. Although the compressor is all-axial, like the earlier General Electric T58, the power turbine shaft is coaxial with the HP shaft and delivers power to the front of the engine, not rearwards. Fourteen compressor stages are required to deliver the required overall pressure ratio. Compressor handling is facilitated by 4 rows of variable stators. Unlike the T58, the power turbine has 2 stages.
The General Electric T31 was the first turboprop engine designed and built in the United States.
The Pratt & Whitney T34 was an American axial flow turboprop engine designed and built by Pratt & Whitney. Its only major application was on the Douglas C-133 Cargomaster.
The Allison T38 was an early turboprop engine developed by Allison Engine Company during the late 1940s. The T38 became the basis for the very successful family of Allison T56 turboprop engine.
The Pratt & Whitney/Allison 578-DX was an experimental aircraft engine, a hybrid between a turbofan and a turboprop known as a propfan. The engine was designed in the 1980s to power proposed propfan aircraft such as the Boeing 7J7 and the MD-91 and MD-92 derivatives of the McDonnell Douglas MD-80. As of 2019, it is still one of only four different contra-rotating propfan engines to have flown in service or in flight testing.
The Allison T61 was a 6,500-shaft-horsepower (4,800-kilowatt) turboprop engine that was to power the 1959 version of the proposed Lockheed Super Hercules military and civil freight aircraft. The U.S. Air Force (USAF) had helped Allison fund the development of the T61 for four years. Lockheed had received orders from Pan American World Airways and Slick Airways for a total of 18 aircraft, but both orders were contingent on the military ordering the aircraft by September 30, 1959, around the date that the USAF's engine development contract expired. The development contract was extended temporarily to November 30, 1959, but the T61 development effort was canceled by January 1960, after USD$37.5 million had been put into the engine's development. Four T61 engines had run on the test stand at the time of cancellation.
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.
References
↑ Proc, Jerry. "CP-140 Aurora". Radio communications and signals: Intelligence in the Royal Canadian Navy. Retrieved 25 August 2020.
↑ Woodley, David R.; Castle, William S. (16–18 October 1973). Heavy lift helicopter main engines. National Aerospace Engineering and Manufacturing Meeting. SAE Technical Papers. SAE Technical Paper Series. Vol.1. Los Angeles, California, U.S.A.: Society of Automotive Engineers (SAE) (published February 1973). doi:10.4271/730920. ISSN0148-7191.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
