Allison T56
{{short description|American-built military turboprop (1954–)}}
{{Use dmy dates|date=May 2022}}
{{Use American English|date=May 2022}}
| {{Infobox aircraft begin
|name= T56 / Model 501 |image= File:Allison T56 turboprop for C-130 2007.JPEG |caption= A T56 mounted on a U.S. Air Force C-130 Hercules receives maintenance. }}{{Infobox Aircraft Engine |type= Turboprop |national origin = United States |manufacturer= Allison Engine Company |first run= |major applications= Convair 580 |developed from = Allison T38 |developed into = Rolls-Royce T406 |variants with their own articles = }} |
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
File:Allison T56-A1 Turboprop Engine Cutaway.jpg
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 military transport aircraft, the T56 was also installed on the Lockheed P-3 Orion maritime patrol aircraft (MPA), Grumman E-2 Hawkeye airborne early warning (AEW) aircraft, and Grumman C-2 Greyhound carrier onboard delivery (COD) aircraft, as well as civilian airliners such as the Lockheed Electra and the Convair 580.
The T56-A-1 delivered to Lockheed in May, 1953, produced only {{cvt|3000|shp|0}}, compared to the required {{cvt|3750|shp|0}} 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 {{cvt|4591|shp|0}} rating with a pressure ratio of 9.25:1 while the T56-A-427 fitted to the E-2 Hawkeye has a {{cvt|5250|shp|0}} rating and a 12:1 pressure ratio. In addition, the T56 produces approximately {{cvt|750|lbf|2}} residual thrust from its exhaust.
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 {{cvt|3,460|shp|kW|adj=pre|propeller}} at a {{cvt|59|F|C R K}} ambient temperature. Successive engine follow-ups included the Series II, which was introduced in 1958 and had an increased power rating of {{cvt|3,755|shp|kW|adj=pre|prop}}, and the Series III, which came out in 1964 and had another power increase to {{cvt|4,591|shp|kW|adj=pre|prop}}. The Series II and III derivatives were developed under military component improvement programs (CIP). By 1965, Allison was proposing the development of Series IV derivatives, but in 1968, the United States Congress restricted CIP work to reliability and maintainability improvements instead of performance improvements. 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 {{cvt|5,912|shp|kW|adj=pre|prop}}, but it was torque-limited to {{cvt|5,250|shp|kW|adj=pre|prop}}.
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. It drives six-bladed scimitar propellers from Dowty Rotol.
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. 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 III engines. As part of the T56 Series 3.5 upgrade, parts from the T56 Series IV engine (such as the compressor seals) and the uncooled turbine blades from the AE 1107C turboshaft would be retrofit into existing T56 Series III casing installations.{{cite news |work=Airforce Technology |title=US approves Rolls-Royce's T56 Series 3.5 engine upgrade for C-130H fleet |url=https://www.airforce-technology.com/news/newsus-approves-rolls-royces-t56-series-35-engine-upgrade-for-c-130h-fleet-4315040/ |date=9 July 2014 |access-date=16 February 2023}} 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, and will be adopted on the P-3 Orion.
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.
=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.{{R|"STOL-BLC"|pp=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 {{cvt|4,591|shp|kW}} 501-M7B turboprops. The 501-M7B produced more power than the normally installed, {{cvt|3,755|shp|kW}} T56-A-7 engines by about 20% (though the 501-M7B was limited to {{cvt|4,200|shp|kW}} 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.
In 1963, an aeroderivative line of industrial gas turbines based on the T56 was introduced in under the 501-K name.{{sfn|Zigmunt|1997|p=[{{GBurl|7wI8SAq6l1cC|p=127}} 127]}} 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.{{sfn|Allison Industrial Gas Turbines|1983}} 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. A marinized turboshaft version of the 501-K is used to generate electrical power onboard all the U.S. Navy's cruisers ({{sclass|Ticonderoga|cruiser|4}}) and almost all of its destroyers ({{sclass|Arleigh Burke|destroyer|4}}).
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. The 50-hour preliminary flight rating test (PFRT) was completed for the T56-A-18 in 1968. 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. 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 {{cvt|42|lb/s}}. After DSTR testing was successful, the 501-M62B engine was further developed into the XT701-AD-700 engine for use on the HLH. The {{cvt|8,079|shp}} XT701 passed the tests required to enter ground and flight testing on the HLH, but funding of the HLH program was canceled in August 1975, when the triple-turbine, tandem-rotor helicopter prototype had reached 95% completion.{{R|"BVFinalReport1980"|p=[https://archive.org/details/DTIC_ADA085290/page/n4 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 {{cvt|7,170|shp}} and adapted for marine, gas compressor, and electrical power generation variants. 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 {{cvt|6,000|shp}} 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 {{cvt|9|ft|m|diameter|adj=mid}} Hamilton Standard single-rotation propfan, containing propfan blades that were swept back 45 degrees at the tips.
Variants
{{Main|Allison T56 variants}}
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, and IV) and the Series 3.5 engine enhancement kit 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.
Applications
Specifications (T56 Series IV)
{{jetspecs
|
|length={{cvt|146.1|in|mm|lk=on}}
|diameter={{cvt|27|in|mm}}
|weight={{cvt|1,940|lb|kg|lk=on}}
|compressor=14 stage axial flow
|combustion=6 cylindrical flow-through
|turbine= 4 stage shared load
|fueltype=Kerosene, jet fuel (Jet A, Jet A-1, JP-4, JP-5, or JP-8), or aviation gasoline (grade 115/145 or lower)
|oil system=1 system (Oil is shared between power section and reduction gearbox.)
|power=SLS, {{cvt|59|F}}, max power: {{cvt|5,912|shp}} (torque limited to {{cvt|5,250|shp}}); {{cvt|25,000|ft|m|adj=mid|altitude}}, Mach 0.5, max continuous power: {{cvt|3,180|shp}}
|thrust=
|eqivshaftpower=
|pressratio=14.5:1
|bypass=
|airmassflow={{cvt|240 - 280|lb|abbr=on}}
|turbinetemp={{cvt|860|°C|°F|lk=on}}
|fuelcon= {{cvt|2,412|lb/h|abbr=on}}
|specfuelcon=SLS, {{cvt|59|F}}, max power: {{cvt|285.3|mg/Wh|lb/hph kg/hph kg/kWh|order=out}}; {{cvt|25,000|ft|m|adj=mid|altitude}}, Mach 0.5, max continuous power: {{cvt|255.5|mg/Wh|lb/hph kg/hph kg/kWh|order=out}}
|power/weight={{cvt|2.75|shp/lb|kW/kg|lk=on}}
|thrust/weight=
}}
See also
{{Portal|Aviation}}
{{Aircontent
|related=
|similar engines=
|lists=
|see also=
}}
References
{{Reflist|refs=
{{cite web |url=https://www.rolls-royce.com/products-and-services/defence-aerospace/transport-tanker-patrol-and-tactical/t56.aspx#section-overview |title=The world's number one large turboprop |publisher=Rolls-Royce plc |access-date=August 25, 2020}}
{{cite news |work=AINonline |title=Advanced Hawkeye marches on |url=https://www.ainonline.com/aviation-news/defense/2019-04-11/advanced-hawkeye-marches |given=David |surname=Donald |date=April 11, 2019 |department=Defense |access-date=September 9, 2020}}
{{cite news |work=AINonline |title=New look for an old warrior |url=https://www.ainonline.com/aviation-news/defense/2018-07-17/new-look-old-warrior |given=David |surname=Donald |date=July 17, 2018 |department=Farnborough Air Show |access-date=August 4, 2020}}
{{cite web |title=Type Certificate Data Sheet E-282 |edition=30th |date=July 25, 2013 |url=https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/37851AD3AA37B87486257BB800525FC6 |publisher=U.S. Department of Transportation (DOT) |website=Federal Aviation Administration (FAA) |access-date=August 11, 2020}}
{{cite news |work=FlightGlobal |title=USAF approves production of Rolls-Royce T56 Series 3.5 upgrade |url=https://www.flightglobal.com/usaf-approves-production-of-rolls-royce-t56-series-35-upgrade/118158.article |date=September 10, 2015 |given=James |surname=Drew |access-date=August 11, 2020 |url-access=limited}}
{{cite web |url=http://www.rolls-royce.com/Images/AE2100_tcm92-6712.pdf |title=AE 2100 turboprop: Power for the Hercules, Spartan, US-2 and SAAB 2000 AEW&C |publisher=Rolls-Royce plc |access-date=November 2, 2012 |archive-url=https://web.archive.org/web/20130217053215/http://www.rolls-royce.com/Images/AE2100_tcm92-6712.pdf |archive-date=2013-02-17 |url-status=dead}}
{{cite web |url=http://www.rolls-royce.com/Images/t56_tcm92-6711.pdf |title=T56: Power for the Hercules, Orion, Hawkeye and Greyhound |publisher=Rolls-Royce plc |access-date=August 25, 2020 |archive-url=https://web.archive.org/web/20130207210055/http://www.rolls-royce.com/Images/t56_tcm92-6711.pdf |archive-date=February 7, 2013 |url-status=dead}}
{{cite manual |publisher=Rolls-Royce plc |title=Training manual: T56/501D Series III |year=2003 |pages=8-1 to 8-24}}
{{cite book |given=Bill |surname=Norton |title=STOL progenitors: The technology path to a large STOL aircraft and the C-17A |year=2002 |url={{GBurl|8zl09uULN8IC|p=42}} |pages=42–[{{GBurl|8zl09uULN8IC|p=43}} 43] |isbn=978-1-56347-576-4 |oclc=50447726 |publisher=American Institute of Aeronautics and Astronautics (AIAA) |doi=10.2514/4.868160}}
{{cite book |issn=0148-7191 |chapter=Advanced gas turbine for marine propulsion model 570-K |publication-date=February 1978 |given1=D.H. |surname1=Stinger |given2=W.A. |surname2=Redmond |title=SAE Technical Paper Series |journal=SAE Technical Papers |year=1978 |volume=1 |publisher=Society of Automotive Engineers (SAE) |doi=10.4271/780702}}
{{cite conference |issn=0148-7191 |title=Heavy lift helicopter main engines |date=October 16–18, 1973 |publication-date=February 1973 |given1=David R. |surname1=Woodley |given2=William S. |surname2=Castle |journal=SAE Technical Papers |series=SAE Technical Paper Series |volume=1 |publisher=Society of Automotive Engineers (SAE) |location=Los Angeles, California, U.S.A. |conference=National Aerospace Engineering and Manufacturing Meeting |doi=10.4271/730920}}
{{cite magazine |issn=0005-2175 |magazine=Aviation Week and Space Technology |title=Power boost planned for STOL C-130 |url=https://archive.org/details/Aviation_Week_1963-01-07/page/n27 |department=Aeronautical engineering |publication-date=January 7, 1963 |given=David A. |surname=Anderton |location=Marietta, Georgia, U.S.A. |pages=54–55, 57}}
{{cite magazine |issn=0015-3710 |magazine=Flight |url=https://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201209.html |url-status=dead |archive-date=December 27, 2014 |archive-url=https://web.archive.org/web/20141227224406/https://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201209.html |title=T56 test-bed: The Allison engine for the C-130 fitted to a Super Constellation |publication-date=April 30, 1954 |page=539}}
}}
Bibliography
- {{cite book |title=Allison, the people and the power: A pictorial history |url={{GBurl|7wI8SAq6l1cC}} |given=Joan Everling |surname=Zigmunt |date=June 1997 |publisher=Turner Publishing Company |isbn=1-56311-315-5 |oclc=37537128}}
- {{cite book |given1=Paul |surname1=Sonnenburg |given2=William A |surname2=Schoneberger |title=Allison power of excellence 1915-1990 |url=https://archive.org/details/allisonpowerofex0000sonn |year=1990 |url-access=limited |isbn=0-9627074-0-6 |oclc=22964244}}
- {{cite web |ref={{SfnRef|Allison Industrial Gas Turbines|1983}} |website=International Power Technology |author=Allison Gas Turbine Operations |title=Allison industrial gas turbines 501-K, 570-K |url=http://intpower.com/wp-content/uploads/1986/10/501-brochure.pdf |date=August 1983 |access-date=August 7, 2020}}
- {{cite magazine |issn=0005-2175 |magazine=Aviation Week & Space Technology |title=New family of Allison engines evolving |url=https://archive.aviationweek.com/issue/19740812/#!&pid=44 |pages=44(4) |publication-date=August 12, 1974 |given=Michael L. |surname=Yaffee |department=Aeronautical engineering |url-access=subscription}}
- {{cite book |ref={{SfnRef|AIA Yearbook|1958}} |author=Aircraft Industries Association, Inc. |title=1957-1958 aircraft year book |url=https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1957-AIRCRAFT-YEAR-BOOK.pdf |edition=39th |year=1958 |publisher=American Aviation Publications, Inc. |access-date=12 August 2020 |archive-date=22 January 2022 |archive-url=https://web.archive.org/web/20220122005549/http://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1957-AIRCRAFT-YEAR-BOOK.pdf |url-status=dead }}
- {{cite magazine |issn=0005-2175 |magazine=Aviation Week |title=Allison moves to boost its airline sales |url=https://archive.org/details/Aviation_Week_1955-12-12/page/n13 |pages=27, 29–31 |publication-date=December 12, 1955 |given=Robert |surname=Hotz |location=Indianapolis, Indiana, U.S.A. |department=Management |volume=63 |number=24}}
External links
{{Commons category|Allison T56}}
- [http://www.rolls-royce.com/defence/products/tactical_aircraft/t56/index.jsp# T56 page at Rolls-Royce website]
{{Allison aeroengines}}
{{Rolls-Royce plc aeroengines}}
{{USAF gas turbine engines}}
{{USAF system codes}}