Lockheed Martin X-35

The Lockheed Martin X-35 was a concept demonstrator aircraft (CDA) developed by Lockheed Martin for the Joint Strike Fighter program. The X-35 was declared winner over the competing Boeing X-32 and a developed, armed version went on to enter production in the early 21st century as the F-35 Lightning II.

X-35 JSF
The X-35A JSF performs flight tests at Edwards Air Force Base, California
Role Concept demonstrator aircraft (CDA)
Manufacturer Lockheed Martin Aeronautics
First flight 24 October 2000[1]
Status Retired
Primary user Defense Advanced Research Projects Agency (DARPA)
Number built 2 (X-35A/B and X-35C)
Developed into Lockheed Martin F-35 Lightning II


Original F-35 Joint Strike Fighter Logo

The Joint Strike Fighter evolved out of several requirements for a common fighter to replace existing types. The actual JSF development contract was signed on 16 November 1996. The JSF program was created to replace various aircraft while keeping development, production, and operating costs down. This was pursued by building three variants of one aircraft, sharing 80% of their parts.[citation needed]

The first is the F-35A, a conventional takeoff and landing (CTOL) variant. It is the smallest and lightest version, and is intended primarily to replace the U.S. Air Force's aging F-16 Fighting Falcons and A-10 Thunderbolt IIs. This is the only version with an internal gun, the GAU-22. This 25 mm cannon is considered an upgrade from the 20 mm M61 Vulcan carried by USAF fighters since the F-104 Starfighter (however the GAU/22 is based on the mechanicals of the larger 30mm GAU-8 Avenger, rather than being a derivative of the M61 Vulcan). Deliveries were scheduled to begin in 2011. The F-35B is the short-takeoff and vertical-landing (STOVL) variant due to replace the U.S. Marine Corps AV-8 Harrier IIs and F/A-18 Hornets, and Royal Air Force/Royal Navy Harrier GR7/GR9s beginning in 2012. The Royal Navy will use this to replace its Harrier GR7s and the RAF replace its Harrier GR9s. The U.S. Marine Corps will use the F-35B to replace both its AV-8B Harrier IIs and F/A-18 Hornets with a design similar in size to the Air Force F-35A, trading fuel volume for vertical flight systems. Like the Harrier, guns will be carried in a pod. Vertical flight is by far the riskiest, and in the end, a decisive factor in design. Lastly, the F-35C, a carrier-based variant, will replace the "legacy" F/A-18 Hornets and serve as a stealthy complement to the F/A-18E/F Super Hornet. It will have a larger, folding wing and larger control surfaces for improved low-speed control, and stronger landing gear for the stresses of carrier landings. The larger wing area provides increased range and payload, achieving much the same goal as the much heavier Super Hornet. The U.S. Navy plans to purchase 480 JSF,[2] with deliveries scheduled to start in 2012.[needs update]

The primary customers and financial backers are the United States and the United Kingdom. Eight other nations are also funding the aircraft's development. Total program development costs, less procurement, are estimated at over US$40 billion, of which the bulk has been underwritten by the United States. Production costs are estimated at US$102 million per unit for 2,400 units.[3]

There are three levels of international participation. The United Kingdom is the sole 'Level 1' partner, contributing slightly over US$2 billion, about 10% of the development costs. Level 2 partners are Italy, which is contributing US$1 billion, and the Netherlands, US$800 million. At Level 3 are Canada, US$440 million; Turkey, US$175 million; Australia, US$144 million; Norway, US$122 million; and Denmark, US$110 million. The levels generally reflect the financial stake in the program, the amount of technology transfer and subcontracts open for bid by national companies, and the priority order in which countries can obtain production aircraft. Israel and Singapore have also joined as Security Cooperative Participants.[4]


X-35 flight video: transition to VTO, hover, short take off, in-flight refuelling, vertical hover and landing.
An X-35B vertical landing (video)

Elements of the X-35 design were pioneered by the F-22 Raptor,[5] and portions of the VTOL exhaust duct design were previously used by the Convair Model 200[6], a 1972 supersonic VTOL fighter requirement for the Sea Control Ship. In June 1994, Lockheed revealed during their bid for the Joint Advanced Strike Technology competition that it had entered into a collaborative relationship consisting of sharing VTOL design data with Yakovlev in 1991; according to Jane's All the World's Aircraft 2000–2001 this was old legacy data from Lockheed was previously used in the cancelled Yak-41M/Yak-141 program which employed a similar vertical takeoff/landing propulsion system.[7][8][9][10][11] Although helmet-mounted display systems have already been integrated into some fourth-generation fighters such as the JAS 39 Gripen, the F-35 will be the first modern combat aircraft in which helmet-mounted displays will replace a head-up display altogether.[12]

During concept definition, two Lockheed airframes were flight-tested: the Lockheed X-35A (which was later converted into the X-35B), and the larger-winged X-35C.[13] Both the Boeing X-32 and X-35 power plants were derived from Pratt & Whitney's F119, with the STOVL variant of the latter incorporating a Rolls-Royce Lift Fan module.[14]

Instead of lift engines or using a direct lift engine like the Rolls-Royce Pegasus in the Harrier Jump Jet, the X-35B was powered by the F119-PW-611 which used an innovative shaft-driven lift fan, patented by Lockheed Martin employee Paul Bevilaqua,[15] and developed by Rolls-Royce.[16] In normal wing-borne flight, the F119-PW-611 was configured as a normal medium-bypass reheated turbofan. The turbofan acted somewhat like a turboshaft engine embedded into the fuselage (but with a much smaller percentage of total heat energy being extracted by the turbine stage), a portion of engine power was extracted via a turbine, and used to drive a shaft running forward via a clutch-and-bevel gearbox to a vertically mounted, contra-rotating lift fan located forward of the main engine in the center of the aircraft (this can also be viewed the same as a high-bypass turbofan but with the low-pressure fan stages mounted remotely from the engine core on an extended, clutched shaft, and creating thrust downwards rather than back around the engine core as in a conventional turbofan).[citation needed] Bypass air from the cruise engine medium-bypass turbofan compressor stages exhausted through a pair of roll-post nozzles in the wings on either side of the fuselage, while the thrust from the lift fan balanced the thrust of the hot core stream exhausting through vectored cruise nozzle at the tail. The X-35B powerplant effectively acted as a flow multiplier, much as a turbofan achieves efficiencies by moving unburned air at a lower velocity, and getting the same effect as the Harrier's huge, but supersonically impractical main fan.[citation needed] Like lift engines, this added machinery was dead weight during flight, but the increased lift thrust enhanced take-off payload by even more. The cool fan also reduced the harmful effects of hot, high-velocity air which could harm runway pavement or an aircraft carrier deck. Though risky and complicated, it was made to work to the satisfaction of DoD officials.[citation needed].

Operational historyEdit

On 20 July 2001, to demonstrate the X-35's unique capability (compared to the X-32),[17] the X-35B STOVL aircraft took off in less than 500 feet (150 m), went supersonic, and landed vertically.[18][19][20]

In the fly-off between the Lockheed Martin X-35 and the Boeing X-32, the former was judged to be the winner. As a result, a contract for System Development and Demonstration (SDD) of the F-35 was awarded on 26 October 2001 to Lockheed Martin,[21] whose X-35 beat the Boeing X-32.

There are a number of differences between the X-35 and F-35.[22]

Aircraft on displayEdit

The X-35B on display at the Steven F. Udvar-Hazy Center.

The X-35A was converted into the X-35B for the STOVL part of the competition. It now resides at the National Air and Space Museum Steven F. Udvar-Hazy Center, near Washington Dulles International Airport in Virginia.[23]

Following the end of the competition, the X-35C was transferred to the Patuxent River Naval Air Museum in St. Mary's County, Maryland.[citation needed]

Specifications (X-35)Edit

Some information is estimated.

X-35A being refuelled in-flight by a KC-135 Stratotanker

Data from Lockheed Martin X-35 Fighter Demonstrator[24]

General characteristics

  • Crew: 1
  • Length: 50.5 ft., 15.39 m (X-35A), 50.8 ft., 15.48 m (X-35C) ()
  • Wingspan: 32.78 ft., 9.99 m (X-35A), 43 ft., 13.1 m (X-35C) ()
  • Height: 13.33ft (4.063 m)
  • Wing area: 450 ft.2, 41.81 m2 (X-35A), 540 ft2, 50.17 m2(X-35C) ()
  • Empty weight: ~22,000 lb (~9979 kg)
  • Powerplant: 1 × Pratt & Whitney F119-PW-611 afterburning turbofan
    • Dry thrust: 28000 lb (dry) (124.5 kN)
    • Thrust with afterburner: ~43000 lb (~191.3 kN)


See alsoEdit

Related development

Aircraft of comparable role, configuration and era

Related lists



  1. ^ "JSF History." JSF. Retrieved 11 January 2011.
  2. ^ "F-35." FAS. Retrieved 9 January 2010.
  3. ^ Merle, Renae. "GAO Questions Cost of Joint Strike Fighter." Washington Post, 16 March 2005. Retrieved: 9 January 2010.
  4. ^ Schnasi, Katherine V. "Joint Strike Fighter Acquisition: Observations on the Supplier Base." US Accounts Office. Retrieved 8 February 2006.
  5. ^ "Vertiflight". Journal of the American Helicopter Society, January 2004.
  6. ^ Bradley, Robert (2013). Convair Advanced Designs II. Manchester, UK: Crécy Publishing. ISBN 978-0-8597917-0-0.
  7. ^ Jackson 2000, p. 700.
  8. ^ "Joint Strike Fighter (JSF)." Jane’s. Retrieved 9 January 2010. Archived 26 February 2009 at the Wayback Machine
  9. ^ Hayles, John. "Yakovlev Yak-41 'Freestyle'." Aeroflight, 28 March 2005. Retrieved: 6 August 2006.
  10. ^ "Lockheed Martin X-35." Aeroflight. Retrieved 20 May 2009.
  11. ^ Gunston, William 'Bill'; Gordon, Yefim (1997). Yakovlev Aircraft since 1924. London, UK: Putnam Aeronautical Books. ISBN 978-1-55750-978-9.
  12. ^ Jenkins, Jim. "Chief test pilot gives brief on F-35." DC military, 2001. Retrieved 6 July 2008.
  13. ^ "History." Joint Strike Fighter (official site). Retrieved 9 January 2010.
  14. ^ "Rolls-Royce LiftSystem demonstrates success in first vertical landing." Rolls-Royce, 19 March 2010. Retrieved 14 April 2012.
  15. ^ Bevilaqua, Paul M; Shumpert, Paul K, Propulsion system for a vertical and short takeoff and landing aircraft (patent), United States: Patent genius, 5209428, retrieved 9 January 2010.
  16. ^ Smith, John and John Kent. "Design News magazine's Engineer of the Year award goes to lift fan inventor at Lockheed Martin." Lockheed Martin, 26 February 2004. Retrieved 9 January 2010.
  17. ^ https://www.flightglobal.com/pdfarchive/view/2001/2001%20-%202278.html?search=X-35B
  18. ^ "X-planes". Nova transcript. PBS. Retrieved 9 January 2010.
  19. ^ "Propulsion system in Lockheed Martin Joint Strike Fighter wins Collier Trophy." Archived 25 May 2011 at the Wayback Machine Lockheed Martin, 28 February 2003. Retrieved 9 January 2010.
  20. ^ https://www.flightglobal.com/pdfarchive/view/2001/2001%20-%202838.html?search=X-35B
  21. ^ Bolkcom, Christopher. "JSF: Background, Status, and Issues," p. CRS-4. DTIC, 16 June 2003. Retrieved 18 September 2010.
  22. ^ http://www.codeonemagazine.com/article.html?item_id=28
  23. ^ "X-35B." National Air and Space Museum. Retrieved: 21 February 2020.
  24. ^ http://www.fighter-planes.com/info/jsf.htm


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External linksEdit