ALF 502/LF 507
ALF 502 removed from a Bombardier Challenger 600-1A11
Type Geared turbofan
National origin United States
Manufacturer Lycoming
Honeywell Aerospace
First run June 1971[1]: 191
Major applications Bombardier Challenger 600
British Aerospace 146
Northrop YA-9
Number built 1,843
Developed from Lycoming T55
The YF102-LD-100 was tested on an AJ Savage in the early 1970s.

The Lycoming ALF 502/LF 507 (later Honeywell ALF 502/LF 507) is a geared turbofan engine produced by Lycoming Engines, AlliedSignal, and then Honeywell Aerospace. The U.S. military designation for the ALF 502 is YF102.


In mid-1970, Avco Lycoming was advertising two Lycoming T55-derived engines, an LTC4B-12 turboprop and an ALF 502A turbofan, as possible powerplants for the U.S. Air Force's A-X close air support aircraft program.[2] Northrop Corporation signed a contract with Avco Lycoming to use the ALF 502A for its entry into the A-X competition, the Northrop YA-9, in January 1971. The engine was given a United States military aircraft engine designation of YF102-LD-100.[1]: 190 Six YF102 engines were built for the YA-9. The 7,500 lbf (33 kN) thrust engines powered the A-9A prototypes for seven months of flight tests in 1972, recording 238 flights and 652 flight hours.[3] These engines were later reused in the C-8A Quiet Short-Haul Research Aircraft (QSRA).

The commercial ALF 502D engine was developed from the military YF102 in 1971. Its 6,500 lbf (29 kN) derated engine had just one booster compressor stage instead of the YF102's two stages, and operated under a lower turbine temperature to improve reliability. The ALF 502D powered the Dassault Falcon 30 prototype from May 1973 into 1975, logging 270 flight hours until Dassault discontinued development of the aircraft model. The ALF 502D was also chosen for the LearStar 600 executive transport aircraft, which eventually became the Canadair CL-600 Challenger. The CL-600 Challenger first flew in November 1978 and was powered by the 7,500 lbf (33 kN) ALF 502L-2, ALF 502L-2A, and ALF 502L-3 variants. The 6,700 lbf (30 kN) ALF 502R-3 variant initially powered the quad-engine British Aerospace 146, which entered service in 1983 and became the ALF 502's biggest customer. A total of 1,019 ALF 502 engines of all variants were produced. The LF 507 series based on the ALF 502R was announced in September 1988. The series initially consisted of the hydromechanically controlled LF 507-1H and the FADEC-controlled LF 507-1F, both offering 7,000 lbf (31 kN) of thrust. Both variants were used on the Avro RJ update of the BAe 146, and the LF 507-1F was also used on the BAe 146.[1]: 192199, 203 818 LF 507 engines were produced.[4]

In 2020, Honeywell sold the type certificate to CFS Aeroproducts Inc. (Arizona), a subsidiary of MRO provider CFS Aeroproducts Ltd (UK), then transferred in January 2021.[5]

Proposed variants

In 1972, Lycoming and NASA published a study describing the ALF504, a 12.5 bypass ratio engine producing 8,370 lbf (3,800 kgf; 37.2 kN) of sea-level thrust at a specific fuel consumption of 0.302 lb/(lbf⋅h) (8.6 g/(kN⋅s)) and a fan tip diameter of 48.0 in (1,220 mm).[6]

Lycoming announced its LF500 family of turbofans in September 1988, starting with the LF507-1H and LF507-1F, which were certificated in October 1991 and March 1992, respectively.[1]: 198 In June 1992, the company outlined improvements to the LF500 family's core, which included a wide-chord fan to move more air, uprated fan gearbox, three-stage power turbine (an increase from two stages), more lighter-weight composite materials, increased diameter in the first three stages of the axial compressor to increase airflow by 17 percent, an improved impeller (centrifugal compressor) with lean-back vanes, a 16-lobe forced exhaust mixer to reduce noise and specific fuel consumption (SFC), an advanced combustor, and a temperature margin increase of 248 °F (120 °C) in the turbine.[7] Lycoming introduced the 500 Series of common core engines of turboprops and turbofans in February 1994 as a derivative of the LF507 to power regional aircraft in the late 1990s.[1]: 198, 199, 200 A turboprop version also was planned for the European Future Large Aircraft military transport (which would eventually become the Airbus A400M). AlliedSignal, which took over Lycoming in October 1994,[8] demonstration tested the common core in December; the core was capable of producing 20,000 lbf (89 kN) of thrust.[9] After losing the competition to power the de Havilland Dash 8-400 regional turboprop, AlliedSignal abandoned the common core effort in July 1995.[10]


Honeywell ALF 502 on an early Challenger 600

The ALF502 is a high bypass turbofan with geared fan, axial-centrifugal flow high pressure compressor, reverse flow annular combustor, two-stage high pressure turbine, two-stage low pressure turbine.[11]


ALF502R-3 (single-stage LP compressor)
ALF502L (two-stage LP compressor)

Proposed Common Core engines

(LF500 family/Lycoming 500 Series/AlliedSignal AS800)


Honeywell LF 507s on an Avro RJ
ALF 502
LF 507


Type Certificate Data Sheet[11]
Variant ALF502R-3 ALF502R-4/5/3A ALF502L/L-2/L-3/L-2A/L-2C/R-6 LF507-1H/1F
Configuration High bypass, geared fan
Fan diameter 40.25 in (1,022 mm)[15]
Gear ratio 2.3:1[16]
Bypass ratio 5.7:1
Compressor 1 LP, 7-stage axial[15] + centrifugal HP 2 LP, 7-stage axial[15] + centrifugal HP
Combustor Reverse flow annular
Turbine Two-stage HP, two-stage LP
Takeoff thrust 6,700 lbf (30 kN) 6,970 lbf (31.0 kN) 7,500 lbf (33 kN) 7,000 lbf (31 kN)
Length 63.66 in (1,617 mm) 65.57 in (1,665 mm)
Height 55.5 in (1,410 mm) 54.5 in (1,380 mm)
Width 47.8 in (1,210 mm) 48.6 in (1,230 mm)
Weight [a] 1,336 lb (606 kg) 1,375 lb (624 kg) (1F: 1,385 lb (628 kg))
LP rpm 7,184 - 7,374
HP rpm 19,280 - 19,760
TSFC 0.406 lb/lbf/h (41.4 kg/kN/h)[15]
Thrust/weight 5.01 5.22 5.45 5.09

See also

Related development

Comparable engines

Geared turbofans

Related lists


  1. ^ includes essential engine accessories but excludes starter, hydraulic pump, integrated drive generator and exhaust nozzle


  1. ^ a b c d e f Leyes, Richard A., II; Fleming, William A. (1999). The history of North American small gas turbine aircraft engines. Reston, VA: National Air and Space Museum and American Institute of Aeronautics and Astronautics (AIAA). ISBN 1-56347-332-1. OCLC 247550535.((cite book)): CS1 maint: multiple names: authors list (link)
  2. ^ Avco Lycoming Division (July 1970). "Proven power, turbofan or turboprop, for any AX configuration". Air Force Magazine. p. 45. ISSN 0730-6784.
  3. ^ Anderson, Fred (1976). "A-X / A-9A close air support aircraft". Northrop: An aeronautical history. Wipf & Stock Publishers. pp. 251–256. ISBN 9781532601460. OCLC 980678030.
  4. ^ Learmount, David; Norris, Guy (August 16, 2004). "Uncontained failure dogs Honeywell LF507 engine". Flight International. ISSN 0015-3710. Retrieved January 30, 2022.
  5. ^ "CFS Aeroproducts Inc. Chooses ATP as Exclusive Partner for ALF502 and LF507 Series Engine Publications" (Press release). ATP. July 27, 2021.
  6. ^ Rauch, Dale (July 1972). Design study of an air pump and integral lift engine ALF-504 using the Lycoming 502 core (Report). National Aeronautics and Space Administration (NASA). hdl:2060/19730004744. alternate url
  7. ^ a b c Warwick, Graham (June 17, 1992). "Lycoming outlines LF500 power increase". Flight International. Vol. 141, no. 4323. p. 8. ISSN 0015-3710. Gale A12271580.
  8. ^ Kandebo, Stanley (November 7, 1994). "AlliedSignal completes Lycoming acquisition". Aviation Week & Space Technology. Vol. 141, no. 19. p. 35. ISSN 0005-2175.
  9. ^ "AlliedSignal runs demo test on former Lycoming 'Common Core' engine". Commuter Regional Airline News. Vol. 12, no. 50. December 26, 1994. pp. 6+. ISSN 1040-5402. Gale A16362047.
  10. ^ "AlliedSignal plans turbine closure". FlightGlobal. July 11, 1995. Retrieved July 16, 2020.
  11. ^ a b "Type certificate data sheet E6NE" (PDF) (15th ed.). Department of Transportation, Federal Aviation Administration (FAA). June 7, 2002.
  12. ^ a b "Textron Lycoming studies 9,000 lb-thrust LF509 for 'developed' RJ100". Commuter Regional Airline News. Vol. 12, no. 28. July 18, 1994. p. 2. ISSN 1040-5402. Gale A15618034.
  13. ^ Sweetman, Bill (October 1994). "New power for regionals". Finance, markets & industry. Interavia. Vol. 49, no. 583. Minneapolis, Minnesota, U.S.A. pp. 16–18. ISSN 1423-3215. OCLC 199793280.
  14. ^ Donoghue, J.A.; Moorman, Robert W.; Reed, Arthur; Woolsey, James P. (October 1992). "Russian deals at Farnborough". Air Transport World. Vol. 29, no. 10. pp. 36+. ISSN 0002-2543. Gale A12736619.
  15. ^ a b c d "ALF 502 turbofan engine". Honeywell Aerospace. November 29, 2010. Archived from the original on March 5, 2012.
  16. ^ Warwick, Graham (25 August 1993). "Engine for change". Flight International. Vol. 144, no. 4384. pp. 39+. ISSN 0015-3710. Gale A14335274.

Further reading