Honeywell T55 Explained

T55
National Origin:United States
First Run:April 1955
Number Built:6,000+

The Honeywell T55 (formerly Lycoming; company designation LTC-4) is a turboshaft engine used on American helicopters and fixed-wing aircraft (in turboprop form) since the 1950s, and in unlimited hydroplanes since the 1980s. As of 2021, more than 6,000 of these engines have been built.[1] It is produced by Honeywell Aerospace, a division of Honeywell based in Phoenix, Arizona, and was originally designed by the Turbine Engine Division of Lycoming Engines in Stratford, Connecticut, as a scaled-up version of the smaller Lycoming T53. The T55 serves as the engine on several major applications including the CH-47-Chinook, the Bell 309, and the Piper PA-48 Enforcer. The T55 also serves as the core of the Lycoming ALF 502 turbofan and the TF series of industrial and marine gas turbines, now produced by Vericor Power Systems. Since the T55 was first developed, progressive increases in airflow, overall pressure ratio, and turbine inlet temperature have more than tripled the power output of the engine.[2] [3] [4]

Variants

Civil and experimental variants

LTC4A-1: Turboprop engine with a power rating of and dry weight of ; was designated the YT55-L-1 after its 50-hour qualification test was completed in December 1957[5]
  • LTC4B-1:
  • LTC4B-2: Geared turboshaft engine with an initial power rating of ; completed a 50-hour qualification test demonstrating in March 1958, and then was designated as the YT55-L-3 with a power rating of [5]
  • LTC4B-7: Ungeared version of the LTC4B-2, with an integral oil cooler and tank; demonstrated in January 1960; the higher power rating resulted from increased turbine inlet temperatures, which came from small modifications learned from YT55-L-1 and YT55-L-3 development experience; completed 50-hour qualification test at power rating in February 1960, after which it was designated as the YT55-L-5; completed its 150-hour qualification test in September 1960, after which its designation changed from YT55-L-5 to the T55-L-5 production engine[5]
  • LTC4B-8: Civil designation for the T55-L-7 military engine; dry weight of [5] also powered the original Bell 214 helicopter as a engine in 1970
  • LTC4B-8D: engine powering the Bell 214A helicopter;[6] uprated from the T55-L-7C; 433 engines produced between 1973 and 1977 for this military helicopter
  • LTC4B-11:similar to L-7 with two-stage gas generator turbine
  • LTC4B-12: Turboprop engine with a power rating of and a weight of, more than the T55-L-11 that it is derived from;[7] brake-specific fuel consumption (BSFC) of
  • LTC4C-2: Civil designation for the YT55-L-1A military turboprop engine[3]
  • LTC4G-3: Turboprop engine with a maximum and normal power rating of ; high-performance version of the T55-L-1[8]
  • LTC4G-4:
  • LTC4K:9-stage compressor
  • LTC4K-2:
  • LTC4M-1:
  • LTC4R-1: Turboprop engine with a power rating of, weight of, pressure ratio of 8.2:1, and a BSFC of
  • PLF1A-2: First experimental high-bypass turbofan engine produced in the United States, initially run in February 1964; two produced; used the engine core of the T55-L-7; geared fan stage, producing a static thrust of ; predecessor of the ALF 502 and LF 507 production turbofans;[9] bypass ratio of 6:1; weight of [10] maximum pressure ratio of 1.4:1 (fan) and 9.5:1 (engine), turbine inlet temperature of, maximum rated air flow for the gas generator and fan of, thrust-specific fuel consumption (TSFC) of [11]
  • PLF1B-2:Turbofan with T55 / LTC4K 9-stage compressor gas generator core
  • PLF1C-1: Turbofan based on the T55-L-7C turboshaft, producing of thrust; length, fan diameter, 6:1 bypass ratio, weight, TSFC of [12]
  • PLF1C-2: Turbofan based on the T55-L-11 turboshaft, producing of thrust; length, fan diameter, 8.2:1 bypass ratio, weight, TSFC of [12]
  • T5508D: Certified September 16, 1975; dry weight ; engine powering the Bell 214B helicopter, which was produced between 1976 and 1981;[13] 88 engines manufactured for that commercial helicopter; commercial version of the LTC4-8D
  • AL5512: Certified November 7, 1980; turboshaft engine with a sea-level power rating of max continuous and 5-minute takeoff; 30-minute power rating of with one engine inoperative; dry weight ;[14] used on the Boeing Model 234 (civilian version of the Chinook);[15] based on the T55-L-712; produced between 1979 and 1985, with 44 engines manufactured; also used on the Boeing Model 360, a technology demonstrator helicopter, in 1987[16]

    • Military variants

    YT55-L-1: Turboprop engine with a maximum and normal power rating of and a pressure ratio of 6:1[17]
  • YT55-L-1A: Turboprop version of the YT55-L-3, producing ; length, diameter, dry weight, pressure ratio 6.5:1, air mass flow, BSFC [3]
  • YT55-L-3: Turboshaft engine with a maximum and normal power rating of and a pressure ratio of 6:1;[17] a geared engine that was initially selected to power the Army Chinook helicopter HC-1B (later designated as the CH-47A) in July 1958 by a joint Air Force/Army team[5]
  • T55-L-5: Turboshaft engine with a maximum and normal power rating of and a pressure ratio of 6:1; high-speed version of the T55-L-3[17] allowed for use on the Chinook instead of the geared YT55-L-3 engine due to August 1958 engine contract modification, with the reduction gearing now provided in the helicopter power transmission system instead of the engine; weight engine; first delivered for the Chinook in August 1960; powered first flight of the Chinook in October 1961; selected for the Curtiss-Wright X-19 tiltrotor aircraft in August 1962;[5] 146 engines manufactured between 1960 and 1963 for the CH-47A
  • T55-L-7: Turboshaft engine with a power rating of and a BSFC of ;[18] completed 150-hour qualification test in September 1962 at a power rating;[5]
  • T55-L-7B: Military and normal power rating of ; used on the CH-47A[19]
  • T55-L-7C: Turboshaft engine with a maximum, military, and normal power rating of ; used on the CH-47B;[19] BSFC of ;[18] passed qualification testing in September 1966[20]
  • YT55-L-9: Turboprop engine with a power rating of, weight of, pressure ratio of 6.4:1, and a BSFC of ; used on the Rockwell YAT-28E;[21] also powered Piper Enforcer prototype aircraft for flight tests in 1971 and 1983-1984[22]
  • T55-L-11: Turboshaft engine with a maximum, military, and normal power rating of ; used on the CH-47C;[19] BSFC of ;[23] completed 50-hour preliminary flight rating test (PFRT) in May 1967[20]
  • T55-L-712: turboshaft engine used on the CH-47D, with production starting in 1978; 849 engines manufactured by 1989
  • T55-L-714: turboshaft engine used on the MH-47E Chinook SOF[24]
  • T55-GA-714A: turboshaft engine used on the CH-47F; low-rate initial production started in December 1997[25]
  • T55-L-714A
  • 5,000 shp (3,729 kW)
    T55-GA-714C: turboshaft engine to be tested on an CH-47F testbed aircraft, offering a 25 percent increase in power output and 10 percent reduction in fuel consumption compared to the T55-GA-714A;[26] initial testing of the first engine began in November 2021[27]
  • T55-L-714C:6,000 shp (4,474 kW)
  • T55-GA-715: A turboshaft engine upgrade kit proposed in 2008 for a growth version of the Chinook[28]
  • HTS7500

    • Industrial and marine variants

    TF20: A marine gas turbine first used in the early 1960's aboard the experimental landing vehicle LVHX-1.[29]
  • TF25: An upgrade of TF20, replaced the original 14 T cane fuel vaporizers with 28 fuel nozzles. Initially rated for, but uprated to by 1969.
  • TF35: Introduced in 1971 with a substantially redesigned turbine including partial core cooling. Changes increased length by . Produced between and .[30]
  • TF40: Turbine blades replaced with lower aspect ratio models, cooling extended to entirety of core and outer shroud. Rated at continuous and intermittent by 1975. Used on JEFF (B) prototype for LCAC.[31] [32]
  • TF40B: Improved TF40 used on production LCAC, introduced better sealing and increased combustion temperatures. Rated at continuous and intermittent.[33] [32]
  • ETF40B: Enhanced TF40B developed in the 1990's to address increasing payload requirements for LCACs with the United States Marine Corps deployments of M1 Abrams in high heat environments. First variant to use CAD in its development, and first to utilize a FADEC. Rated at continuous and intermittent.[34]
  • TF50A: A developmental contemporary of ETF40B designed for commercial marine applications, using the compressor of ETF40B and a combustor and gas generator derived from the LF 507 turbofan. Rated at continuous and intermittent.[35]
  • TF60B: Development started in 2004, designed to provide 30% more power than ETF40B. Competed to power the Ship-to-Shore Connector but lost to Rolls-Royce MT7.[36]

    • Applications

    T55/LTC4
    HTS7500
    TF series

    Bibliography

    External links

    Notes and References

    1. Web site: Honeywell to provide more T55 engines for Chinooks - Shephard Media. 2021-10-28. www.shephardmedia.com. en.
    2. 0015-3710 . . 1,500 s.h.p. Lycoming . 432 . April 5, 1957 . dead . April 26, 2019 . https://web.archive.org/web/20190426205234/https://www.flightglobal.com/pdfarchive/view/1957/1957%20-%200430.html?search=T55.
    3. 0015-3710 . . Aero engines 1959... . 406 . March 20, 1959 . dead . April 26, 2019 . https://web.archive.org/web/20190426205234/https://www.flightglobal.com/pdfarchive/view/1959/1959%20-%200813.html?search=T55.
    4. 0015-3710 . . Congress supports Chinook upgrade . October 23–29, 1996 . 22 . dead . April 3, 2016 . https://web.archive.org/web/20160403121328/https://www.flightglobal.com/pdfarchive/view/1996/1996%20-%202830.html?search=T55-L-714A.
    5. Lycoming Afield . T55 engine development history . Insert . June 1963 . Art . Beaman . 1 . 3.
    6. 0002-2500 . Air Progress . Military report . September 1975 . 72 . 37 . 9.
    7. 0730-6784 . . [{{GBurl|w-U9AQAAIAAJ|pg=RA6-PA45}} Proven power, turbofan or turboprop, for any AX configuration ]. July 1970 . 45 . Avco Lycoming Division . Avco Lycoming.
    8. Book: Aerospace Year Book . 1962 . 43rd . 412 . Engines in production . American Aviation Publications, Inc. . 2021-11-03 . 2021-12-25 . https://web.archive.org/web/20211103012348/https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1962-AEROSPACE-YEAR-BOOK.pdf#page=413 . dead .
    9. Book: [{{GBurl|FW_50wm8VnMC|p=235}} Air warfare: An international encyclopedia: A-L ]. Walter J. . Boyne . ABC-CLIO . 2002 . 235 . 978-1-57607-345-2.
    10. Web site: Lycoming PLF1A-2 turbofan engine . . December 31, 2021.
    11. Roy D. . Stern . February 1971 . ARL 71–0036 . A description of a multichannel ejector test facility and preliminary test results . Appendix F: PLF1A-2 propulsion characteristics summary . https://hdl.handle.net/2027/osu.32435065948978?urlappend=%3Bseq=70%3Bownerid=115614312-78 . 60 . 2027/osu.32435065948978 . 48861178.
    12. Book: Aerospace Year Book . 1969 . 47th . R–336 to R–338 . Engines (turbine) . Books, Inc. . 2022-01-13 . 2021-11-03 . https://web.archive.org/web/20211103012225/https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1969-AEROSPACE-YEAR-BOOK.pdf#page=619 . dead .
    13. News: . Erickson acquires type certificate for Bell 214 . September 6, 2020 . Mark . Huber . General Aviation.
    14. . Honeywell (AlliedSignal, Textron Lycoming) . Type Certificate Data Sheet No. E4NE . 6th . February 1, 2000 . December 26, 2021 . December 26, 2021 . https://web.archive.org/web/20211226213205/https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/062b3f37fbca282a862568f8006554dc/$FILE/E4NE.pdf . dead .
    15. Web site: . Model 234 Chinook: Historical snapshot . December 27, 2021.
    16. Web site: American Helicopter Museum & Education Center . Boeing Model 360 . January 21, 2022.
    17. Book: Aerospace Year Book . 1961 . 42nd . 407 . Engines in production . American Aviation Publications, Inc. . 2021-12-25 . 2021-11-03 . https://web.archive.org/web/20211103012404/https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1961-AEROSPACE-YEAR-BOOK.pdf#page=412 . dead .
    18. Book: Aerospace Year Book . 1967 . 45th . R–281 . Engines (turbine) . Spartan Books . 2021-11-03 . 2021-12-26 . https://web.archive.org/web/20211103012207/https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1967-AEROSPACE-YEAR-BOOK.pdf#page=540 . dead .
    19. 0004-2471 . United States Army Aviation Digest . The Chinook story . August 1972 . 8–14 . Leo . Burnett . 2027/osu.32435062845565 . 505677169 . 18 . 8.
    20. 0004-2471 . United States Army Aviation Digest . The improved Chinook . December 1967 . 22–27 . Truxtun R. . Baldwin . 2027/mdp.39015024192794 . 428479866 . 13 . 12.
    21. Book: Aerospace Year Book . 1968 . 46th . R–317 to R–319 . Engines (turbine) . Books, Inc. . 2021-11-03 . 2022-01-13 . https://web.archive.org/web/20211103042813/https://www.aia-aerospace.org/wp-content/uploads/2016/06/THE-1968-AEROSPACE-YEAR-BOOK.pdf#page=582 . dead .
    22. 0886-2257 . . The Cub's badass big brother . December 2014 . Robert . Bernier.
    23. Book: Aerospace Year Book . 1970 . 48th . R–326 . Engines (turbine) . Books, Inc. .
    24. Book: Boyne, Walter J. . 2003 . 199 . [{{GBurl|ubFfDpQ5lrEC|p=199}} Operation Iraqi Freedom: What went right and why; what went wrong and why ]. Macmillan . 0-765-31038-4 . 676715685.
    25. Book: 0-16-049913-5 . Weapon systems: United States Army 1999 . CH-47 Chinook/Improved Cargo Helicopter (ICH) recapitalization . https://asc.army.mil/docs/wsh2/1999-wsh.pdf#page=255 . . 1999 . 241 . U.S. Government Printing Office . 51357882.
    26. News: . US Army to demonstrate its upgraded Chinook engine . June 4, 2020 . January 22, 2022.
    27. News: AVweb . Honeywell begins testing next-gen T55 engine . December 3, 2021 . Kate . O'Connor.
    28. 0015-3710 . . US Army launches next-generation heavylift helicopter engine programme . July 28, 2008 . Stephen . Trimble . limited.
    29. Schuegenpflug, Hermann, Wilcoxson, Tony, Luz, Michael (2010). FROM THE JEFF (B) TO THE SSC AND BEYOND, TF MARINE GAS TURBINES A DEVELOPMENT STUDY. Paper Number GT2010-23659. The American Society of Mechanical Engineers. p. 2
    30. Schuegenpflug, Hermann, Wilcoxson, Tony, Luz, Michael (2010). FROM THE JEFF (B) TO THE SSC AND BEYOND, TF MARINE GAS TURBINES A DEVELOPMENT STUDY. Paper Number GT2010-23659. The American Society of Mechanical Engineers. p. 2, 3
    31. Schuegenpflug, Hermann, Wilcoxson, Tony, Luz, Michael (2010). FROM THE JEFF (B) TO THE SSC AND BEYOND, TF MARINE GAS TURBINES A DEVELOPMENT STUDY. Paper Number GT2010-23659. The American Society of Mechanical Engineers. p. 3, 4
    32. Silver, S., Lauriat, T. B. (1983). THE TF40B, A 4000 HP CLASS MARINE GAS TURBINE FOR THE U.S. NAVY LCAC (PDF). Paper Number 83-GT-18. The American Society of Mechanical Engineers. p. 4
    33. Schuegenpflug, Hermann, Wilcoxson, Tony, Luz, Michael (2010). FROM THE JEFF (B) TO THE SSC AND BEYOND, TF MARINE GAS TURBINES A DEVELOPMENT STUDY. Paper Number GT2010-23659. The American Society of Mechanical Engineers. p. 4, 5
    34. Schuegenpflug, Hermann, Wilcoxson, Tony, Luz, Michael (2010). FROM THE JEFF (B) TO THE SSC AND BEYOND, TF MARINE GAS TURBINES A DEVELOPMENT STUDY. Paper Number GT2010-23659. The American Society of Mechanical Engineers. p. 5, 6
    35. Schuegenpflug, Hermann, Wilcoxson, Tony, Luz, Michael (2010). FROM THE JEFF (B) TO THE SSC AND BEYOND, TF MARINE GAS TURBINES A DEVELOPMENT STUDY. Paper Number GT2010-23659. The American Society of Mechanical Engineers. p. 6, 7
    36. Schuegenpflug, Hermann, Wilcoxson, Tony, Luz, Michael (2010). FROM THE JEFF (B) TO THE SSC AND BEYOND, TF MARINE GAS TURBINES A DEVELOPMENT STUDY. Paper Number GT2010-23659. The American Society of Mechanical Engineers. p. 7, 8
    37. Web site: Expert Witness . 2025-05-24 . Smithsonian Magazine . en.
    38. Book: Hopkins III, Robert S. . The KC-135 Stratotanker; More Than Just a Tanker . 1997 . Midland Publishing Limited . 978-1-85780-069-2.

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