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A Williams FJ44-3ATW turbofan engine
Type Turbofan
National origin United States
Manufacturer Williams International
First run 1985[1]
Major applications Beechcraft Premier I
Cessna CitationJet
Piper PiperJet Altaire
Saab 105
Grob G180 SPn
Pilatus PC-24
Developed into Williams FJ33

The Williams FJ44 is a family of small, two-spool, turbofan engines produced by Williams International for the light business jet market. Until the recent boom in the very light jet market, the FJ44 was one of the smallest turbofans available for civilian applications. Although basically a Williams design, Rolls-Royce was brought into the project at an early stage to design, develop, and manufacture an air-cooled high-pressure (HP) turbine for the engine. The FJ44 first flew on July 12, 1988 on the Scaled Composites/Beechcraft Triumph aircraft.

The Williams FJ33 is a newer, smaller engine based on the basic FJ44 design.


Production started in 1992 with the 1,900 lbf (8.5 kN) thrust FJ44-1A. The FJ44-1C is derated to 1,500 lbf (6.7 kN). The uprated to 2,300 lbf (10 kN) FJ44-2A was introduced in 1997. The 2,820 lbf (12.5 kN) thrust FJ44-3A was introduced in 2004. In 2005, a new low end version, the FJ44-1AP, was introduced, with a 1,965 lbf (8.74 kN) takeoff thrust. Released in 2007 was the new 3,600 lbf (16 kN) thrust FJ44-4. In 2010 this engine was in use on the Cessna CJ4, and since 2018 also on the new Pilatus PC-24.


The FJ44-1A has a single stage blisk fan plus a single intermediate pressure (IP) booster stage, both driven by a 2 stage low pressure (LP) turbine, and supercharging a single stage centrifugal high pressure (HP) compressor, driven by a single stage uncooled high pressure (HP) turbine. The combustor is an impingement cooled annular design. Fuel is delivered to the combustor through an unusual rotating fuel nozzle system, rather than the standard fuel-air mixers or vapourisers. The bypass duct runs the full length of the engine. The FJ44-2A has two additional booster compressor stages.


1,900 lbf (8.5 kN) thrust, production started in 1992, 20.9 in (530 mm) diameter fan, SFC at full thrust at SLS, ISA is understood to be 0.456 lb/(hr lbf),
1,965 lbf (8.74 kN) takeoff thrust, introduced in 2005, 5% better specific fuel consumption, lower internal temperatures, similar to the -1A with a higher pressure ratio fan, a new combustor and LP turbine, a new full length bypass duct/exhaust mixer and a dual channel FADEC.[2]
1,500 lbf (6.7 kN) thrust, derated version of the FJ44-1A, SFC of 0.460 lb/lbf/h (46.9 kg/kN/h).[3][4]
2,300 lbf (10 kN) thrust, introduced in 1997, larger 21.7 in (550 mm) diameter fan, with two additional booster stages to increase core flow, centrifugal compressor throttled-back aerodynamically to a lower HPC pressure ratio than the -1, exhaust mixer and a fuel electronic control unit.[5]
2,400 lbf (11 kN) thrust, similar to the -2A with an integrated hydromechanical fuel control unit.
2,820 lbf (12.5 kN) thrust, 2004 introduction, similar to the -2A with a larger fan and dual channel FADEC unit.[6]
2,490 lbf (11.1 kN) thrust, derated -3A.
3,000 lbf (13 kN) thrust.[7]
3,600 lbf (16 kN) thrust, released in 2007, hi-tech fan of larger diameter than the -3 unit.[8] Used on the Cessna CJ4 and the Pilatus PC-24.
Williams-Rolls F129
Military designation for the derated FJ44-1C with 1500lbf (6.672kN) power output.


2,000 CitationJets have been delivered by June 2017[9]
Variant Application Type Deliveries
FJ44-1[10] Cessna CitationJet CJ1/CJ1+/M2 Business Jet 1993-
SAAB Sk60 Jet Trainer re-engine
FJ44-2[11] Beechcraft Premier 1A Business Jet 2001-2012
Cessna CitationJet CJ2 Business Jet 2000-2005
Cessna Citation 501SP Business Jet re-engine[a]
Cessna Citation 550 Business Jet re-engine[b]
Scaled Composites Proteus Experimental 1998
Syberjet SJ30 Business Jet 2007-2009
Learjet 25 Business Jet re-engine[c]
Virgin Atlantic GlobalFlyer Experimental 2005
FJ44-3[12] Cessna CitationJet CJ2+/CJ3+ Business Jet 2004-
Cessna Citation 550 Business Jet re-engine[d]
Nextant 400XTi Business Jet re-engine
FJ44-4[13] Cessna CitationJet CJ4 Business Jet 2010-
Hawker 400XPR Business Jet re-engine
Pilatus PC-24 Business Jet 2018-
FJ44-4M Aero L-39NG Jet Trainer
Light attack aircraft
not delivered[clarification needed] Alenia Aermacchi M-345 Jet Trainer Under development
Cessna 526 CitationJet[e] Jet Trainer 2 prototypes
Eviation Jets EV-20 Vantage Jet Business Jet 1 prototype
Grob G180 SPn Business Jet 4 prototypes
Hawker 200 Business Jet Cancelled
Lockheed Martin Polecat Drone Crashed
Lockheed Martin RQ-3 DarkStar Drone Cancelled
Piper PA-47 PiperJet/Altaire Business Jet 1 prototype
Scaled Composites Triumph Business Jet 1 prototype


Type Certificate Data Sheet[14]
Variant FJ44-1AP[15] FJ44-2[16] FJ44-3[17] FJ44-4[18]
Configuration Twin-spool turbofan with 1-stage fan and annular combustor
LP compressor 1-stage axial 3-stage axial
HP compressor 1-stage centrifugal
Turbine 1-stage HP, 2-stage LP
Thrust 1,900–2,100 lbf (8.5–9.3 kN) 2,300–2,400 lbf (10.2–10.7 kN) 3,000 lbf (13.3 kN) 3,600 lbf (16.0 kN)
Weight 460 lb (209 kg) 520–530 lb (236–240 kg) 516–535 lb (234–243 kg) 658 lb (298 kg)
Length 41.4 in (105 cm) 47.2 in (120 cm) 48.0 in (122 cm) 52.8 in (134 cm)
Diameter 20.7 in (53 cm) 21.8 in (55 cm) 23.0 in (58 cm) 25.3 in (64 cm)

See also

Related development

Related lists


  1. ^ "Williams Imagines Future Concept". Flight International. 12 October 1985. Retrieved 6 April 2017.
  2. ^ FJ44-1AP at, Accessed 2006-05-07
  3. ^ FJ44-1 at, Accessed 2006-05-07
  4. ^ FJ44 for military trainer aircraft at, Accessed 2006-05-07
  5. ^ FJ44-2 at, Accessed 2006-05-07
  6. ^ FJ44-3 at, Accessed 2006-05-07
  7. ^ Williams Fanjet Family, Accessed 2020-02-20
  8. ^ FJ44-4 at, Accessed 2010-03-12
  9. ^ "Textron Aviation celebrates light jet leadership with 2,000th delivery for Cessna CJ family" (Press release). Textron Aviation. June 8, 2017.
  10. ^ "Airplanes with the FJ44-1 Engine". Williams International.
  11. ^ "Airplanes with the FJ44-2 Engine". Williams International.
  12. ^ "Airplanes with the FJ44-3 Engine". Williams International.
  13. ^ "Airplanes with the FJ44-4 Engine". Williams International.
  14. ^ "Type Certificate Data Sheet NO. E3GL" (PDF). FAA. October 4, 2018.
  15. ^ "FJ44-1AP". Williams International.
  16. ^ "FJ44-2". Williams International.
  17. ^ "FJ44-3". Williams International.
  18. ^ "FJ44-4". Williams International.


  1. ^ Sierra Industries FJ44 Stallion
  2. ^ Sierra Industries FJ44 Eagle II
  3. ^ SpiritWing
  4. ^ Sierra Industries Super II/S-II
  5. ^ as Williams-Rolls F129