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The F135-PW-600 engine with lift fan, roll posts, and rear vectoring nozzle, as designed for the F-35B V/STOL variant, at the Paris Air Show, 2007
Type Turbofan
Manufacturer Pratt & Whitney
Major applications F-35 Lightning II
Developed from Pratt & Whitney F119

The Pratt & Whitney F135 is an afterburning turbofan developed for the F-35 Lightning II single-engine strike fighter. The F135 family has several distinct variants, including a conventional, forward thrust variant and a multi-cycle STOVL variant that includes a forward lift fan. The first production engines are scheduled to be delivered in 2009.[1]



The origins of the F135 lie with Lockheed Martin's Skunk Works's efforts to devlop a stealthy STOVL strike fighter for the U.S. Marine Corps under a 1986 DARPA program. Lockheed employee Paul Bevilaqua developed and patented[2] a concept aircraft and propulsion system, and then turned to Pratt & Whitney (P&W) to build a demonstrator engine. The demonstrator used the first stage fan from a F119 engine for the lift fan, the engine fan and core from the F100-220 for the core, and the larger low pressure turbine from the F100-229 for the low pressure turbine of the demonstrator engine. The larger turbine was used to provide the additional power required to operate the lift fan. Finally, a variable thrust deflecting nozzle was added to complete the "F100-229-Plus" demonstrator engine. This engine proved the lift-fan concept and led to the development of the current F135 engine.[3]

The first production propulsion system for operational service is scheduled for delivery in 2007. The F-35 will serve the U.S., UK, and other international customers. The initial F-35s will be powered by the F135, but GE/Rolls-Royce team is developing the F136 turbofan as an alternate engine for the F-35 as of July 2009. The Initial Pentagon planning required that after 2010, for the Lot 6 aircraft, the engine contracts will be competitively tendered. However since 2006 the Defense Department has requested no funding for the alternate F136 engine program, but Congress has maintained program funding.[4]

The F135 team is made up of Pratt & Whitney, Rolls-Royce and Hamilton Sundstrand. Pratt & Whitney is the prime contractor and handles main engine, and systems integration. Rolls-Royce is responsible for the vertical lift system for the STOVL aircraft system. Hamilton Sundstrand is responsible for the electronic engine control system, actuation system, PMAG, gearbox, health monitoring systems, and fuel system,

As of 2009, P&W is developing a more durable version of the F135 engine to increase the service life of key parts. These parts are primarily in the hot sections of the engine (the combustor and high pressure turbine blades specifically) where current versions of the engine are running hotter than expected, reducing life expectancy. The test engine is designated XTE68/LF1, and testing is expected to begin in 2010.[5] This redesign has caused “substantial cost growth.”[6]


The F135 is a two-shaft engine that has a three-stage fan (low pressure) and a six-stage high pressure (HP) compressor. The hot section features an annular combustor with a single-stage HP turbine unit and a two-stage LP turbine. The afterburner features a variable converging-diverging nozzle.[7]

The conventional and carrier aviation engines, the F135-PW-100 and F135-PW-400, have a maximum (wet) thrust of approximately 43,000 lbf (191 kN) and a dry thrust of approximately 28,000 lbf (125 kN). The major difference between the the -100 and -400 models is the use of salt-corrosion resistant materials.[7]

The STOVL variant, F135-PW-600, delivers the same 43,000 lbf (191 kN) of wet thrust as the other types in its conventional configuration. In STOVL configuration, the engine produces 18,000 lbf (80.1 kN) of lift thrust. Combined with thrust from the LiftFan (20,000 lbf/89.0 kN) and two roll posts (1,950 lbf/8.67 kN each), the Rolls-Royce LiftSystem produces a total of 41,900 lbf (186 kN) of thrust, almost the same vertical lifting force for slow speed flight as the same engine produces at maximum afterburner, without the extreme fuel use or exhaust heat as wet thrust.[8]

The STOVL variant engages a clutch to extract around 35,000 shp (26,000 kW) from the LP turbine to turn the forward lift fans. Power is transferred through a bevel gearbox, to drive two vertically mounted contra-rotating fans. The uppermost fan is fitted with variable inlet guide vanes and the fan discharges cool exhaust through a nozzle on the underside of the aircraft. This cool air from the lift fan has the added benefit of preventing hot exhaust gases from the core section from being reingested into the engine while hovering. Finally, bypass duct air is sent to a pair of roll post nozzles and the core stream discharges downwards via a thrust vectoring nozzle at the rear of the engine.[3]

Improving engine reliability and ease of maintenance is a major objective of the F135. The engine has fewer parts than similar engines which should help improve reliability. All line-replaceable components (LRCs) can be removed and replaced with a set of six common hand tools.[9] Additionally, the F135's health management system is designed to provide real time data to maintainers on the ground, allowing them to troubleshoot problems and prepare replacement parts before the aircraft returns to base. According the Pratt & Whitney, this data may help drastically reduce troubleshooting and replacement time, as much as 94% over legacy engines.[10]

The F135/F136 engines are not designed to supercruise.[11]


  • F135-PW-100 : Used in the F-35A Conventional Take-Off and Landing variant
  • F135-PW-400 : Used in the F-35C carrier variant
  • F135-PW-600 : Used in the F-35B Short Take-Off Vertical Landing variant

Specifications (F135-PW-100)


General characteristics

  • Type: Afterburning Turbofan
  • Length: 229 in (5.59 m)
  • Diameter: 51 in (1.29 m)
  • Dry weight: classified / unpublished




  1. ^ "F135 Engine Exceeds 12,000 Engine Test Hours as Pratt & Whitney Prepares to Deliver First Production Engines" (2009). Pratt & Whitney press release. July 28, 2009. PR Newswire Link
  2. ^ "Propulsion system for a vertical and short takeoff and landing aircraft", United States Patent 5209428. PDF of original :
  3. ^ a b Bevilaqua, Paul M. (2005). One-page preview of] Joint Strike Fighter Dual-Cycle Propulsion System. Journal of Propulsion and Power, Vol. 21, 5. p. 778-783.
  4. ^ Trimble, Stephen. "US Senate axes F-35 alternate engine"., 23 July 2009.
  5. ^ Harrington, Caitlin. (2009) Pratt & Whitney starts development of new F-35 test engine. Jane's Defence Weekly, March 27, 2009.
  6. ^ Donley: No JSF Alternatives Exist
  7. ^ a b "The Pratt & Whitney F135". Jane's Aero Engines. Jane's Information Group, 2009 (subscription version, dated 10 July 2009).
  8. ^ LiftSystem. Rolls-Royce. Retrieved: 29 July 2009.
  9. ^ Pratt & Whitney F135 Press release
  10. ^ Rajagopalan, R., Wood, B., Schryver, M. (2003). Evolution of Propulsion Controls and Health Monitoring at Pratt and Whitney. AIAA/ICAS International Air and Space Symposium and Exposition: The Next 100 Years. 14-17 July 2003, Dayton, Ohio. AIAA 2003-2645.
  11. ^ Frequently Asked Questions about JSF, JSF.MIL retrieved January 2010


  • Jane's Information Group. Pratt & Whitney F135. Jane's Aero Engines. Modified 10 July 2009.

External links


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