Lockheed Martin X-35
|The X-35A JSF performs flight tests at Edwards Air Force Base, California|
|Manufacturer||Lockheed Martin Aeronautics |
|Primary user||Defense Advanced Research Projects Agency (DARPA)|
|Variants||F-35 Lightning II|
The X-35 was an experimental aircraft by Lockheed Martin for the Joint Strike Fighter Program. It was declared the winner over the Boeing X-32 and went on to enter production in the early 21st century as the F-35 Lightning II.
The contract for System Development and Demonstration (SDD) was awarded on 26 October 2001 to Lockheed Martin, whose X-35 beat the Boeing X-32. DoD officials and the UK Minister of Defence Procurement said the X-35 consistently outperformed the X-32, although both met or exceeded requirements.
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:
- F-35A, a conventional takeoff and landing (CTOL) variant slated to replace U.S. Air Force (USAF) F-16 Fighting Falcons, beginning in 2011.
- F-35B, a short-takeoff and vertical-landing (STOVL) variant slated to replace the U.S. Marine Corps (USMC) AV-8 Harrier IIs and F/A-18 Hornets, and Royal Air Force (RAF)/Royal Navy (RN) Harrier GR7/GR9s beginning in 2012.
- F-35C, a carrier-based variant slated to replace U.S. Navy (USN) F/A-18 Hornets (A/B/C/D variants only) beginning in 2012.
The primary customers and financial backers are the United States and the United Kingdom. Eight other nations are also funding the aircraft's development and will decide in 2006 whether or not to purchase it. Total program development costs, less procurement, are estimated at over US$40 billion, of which the bulk has been underwritten by the United States.
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.
Elements of the F-35 design were pioneered by the F-22 Raptor. The F-35 appears to be a trimmer and sleeker one-engine sibling of the two-engine F-22. The exhaust duct design was inspired by the General Dynamics Model 200, a 1972 VTOL aircraft designed for the Sea Control Ship. Lockheed had a teaming relationship with the Yakovlev Design Bureau on their bid for the Joint Advanced Strike Technology competition. This has fueled speculation that the overall design of the F-35 was heavily influenced by the Yak-141,(In the Aircraft Museum at aerospaceweb.org) however, the two aircraft are very different.
Some specific improvements over current-generation fighter aircraft are:
- Durable, low-maintenance stealth technology;
- Integrated avionics and sensor fusion that combine information from off- and onboard sensors to increase the pilot's situational awareness and improve identification and weapon delivery, and to relay information quickly to other command and control (C2) nodes;
- Low life-cycle costs.
Although helmet-mounted display systems have already been integrated into some fourth-generation fighters like the Swedish-manufactured JAS 39 Gripen, the F-35 will be the first modern combat aircraft in which helmet-mounted displays will replace a heads-up display altogether.
The F-35A is the smallest, 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-12/U. This 25 mm cannon is an upgrade from the 20 mm M61 Vulcan carried by USAF fighters since the F-104 Starfighter.
The X-35A was converted into the X-35B for the VSTOL part of the competition. It now resides at the Udvar Hazy Museum, near Dulles Airport in Virginia.
The F-35B STOVL aircraft is intended to replace the vertical flight Harrier, which was the world's first operational short-takeoff / vertical-landing fighter. The Royal Navy will use this to replace its Sea Harrier FA2s and the RAF's GR9s. The U.S. Marine Corps will use the F-35B to replace both its AV-8B Harriers and F/A-18 Hornet fighters 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.
Instead of lift engines or rotating nozzles on the engine fan like the AV-8 Harrier, the F-35B uses an innovative shaft-driven Lift Fan, patented by Lockheed Martin and developed by Rolls-Royce. Somewhat like a turboprop embedded into the fuselage, engine shaft power is diverted 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. Bypass air from the cruise engine turbofan exhausts through a pair of roll-post nozzles in the wings on either side of the fuselage, while the lift fan balances the vectoring cruise nozzle at the tail.
In effect, the F-35B power plant acts 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. Like lift engines, this added machinery is dead weight during flight, but increased lifting power increases takeoff payload by even more. The cool fan also reduces the harmful effects of hot, high-velocity air which can harm runway pavement or an aircraft carrier deck. Though risky and complicated, it was made to work to the satisfaction of DOD officials. Unlike Boeing's entry, the prototype was able to demonstrate a historic flight starting with a short takeoff, transitioning to supersonic flight, and ending with a vertical landing.
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. 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.
Arguably the most persuasive demonstration of the X-35's capability was the final qualifying Joint Strike Fighter flight trials, in which the X-35B STOVL aircraft took off in less than Template:Convert, went supersonic, and landed vertically.
The Naval F-35C variant will replace the F/A-18A, -B, -C, and -D Hornets, which replaced subsonic but long-ranged attack types such as the A-7 Corsair and A-6 Intruder. It will also 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, with twice the range on internal fuel compared with the F/A-18C, achieving much the same goal as the much heavier Super Hornet. The U.S. Navy plans to purchase 480 JSF.
Following the end of the competition, the X-35C was transferred to the Patuxent River naval Air Station Museum in St Mary's county, MD where it reposes near the X-32B VSTOL prototype.
Some information is estimated.
Notes and references
- Washington Post article, 15 March 2005
- Katherine V. Schnasi Joint Strike Fighter Acquisition: Observations on the Supplier Base US Accounts Office. Retrieved 8 February 2006.
- Vertiflight (Jan. 2004). Journal of the American Helicopter Society.
- John Hayles. Yakovlev Yak-41 'Freestyle'. Aeroflight. March 28, 2005. Accessed August 6, 2006.
- Jenkins, Jim (2001). Chief test pilot gives brief on F-35. dcmilitary.com. Retrieved on 2006-04-10.
- Lockheed Martin. Design News magazine's Engineer of the Year award goes to lift fan inventor at Lockheed Martin. February 26, 2004.
- Joint Strike Fighter official site - History page
- PBS: Nova transcript "X-planes"
- http://www.fas.org/man/dod-101/sys/ac/f-35.htm FAS F-35
- Spick, Mike (2002), The Illustrated Directory of Fighters. Salamander ISBN 1-84065-384-1
- PBS NOVA: Battle of the X-Planes (JSF selection)
- F-35 JSF news articles
- Official homepage
- Lockheed Martin JSF photo gallery
- Article in The Australian about program difficulties
- Data on the F-35 Joint Strike Fighter (JSF) by the Federation of American Scientists
X-35 flight (video) (file info)
- X-35 flight, video of transition to VTOL configuration, hover, take off in STOVL configuration, in-flight re-fuelling, vertical hover and landing.
F-35 gun test (video) (file info)
- Test firing of F-35 gun.
X-35 vertical landing (video) (file info)
- Vertical landing (video)
- Problems seeing the videos? See media help.
- List of fighter aircraft
- List of experimental aircraft
- List of military aircraft of the United States
- Comparison of 21st century fighter aircraft
- Future Offensive Air System
- Joint Combat Aircraft
- Advanced Tactical Fighter
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