Lockheed Martin X-35

X-35 JSF
The X-35A JSF performs flight tests at Edwards Air Force Base, California.
Role	Prototype/Demonstrator
Manufacturer	Lockheed Martin Aeronautics Northrop Grumman BAE Systems
First flight	24 October 2000[1]
Introduction	NA
Status	Retired (Museum)
Primary user	Defense Advanced Research Projects Agency (DARPA)
Produced	NA
Number built	2
Developed into	F-35 Lightning II

The X-35 was an experimental aircraft developed 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.

Contents 1 Development 1.1 Requirement 1.2 International participation 2 Design 3 Variants 3.1 X-35A (tail number 301) 3.2 X-35B (tail number 301) 3.3 X-35C (tail number 300) 4 Specifications (F-35) 6 Gallery

Development

Main article: Joint Strike Fighter Program

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 contract for System Development and Demonstration (SDD) was awarded on 26 October 2001 to Lockheed Martin,^[2] whose X-35 beat the Boeing X-32. US DoD officials and the UK Minister of Defence Procurement said the X-35 consistently outperformed the X-32, although both met or exceeded requirements.^{[verification needed]}

Requirement

Original F-35 Joint Strike Fighter Logo

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.

International participation

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 or later 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.^[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.[1] 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]

Design

Elements of the F-35 design were pioneered by the F-22 Raptor. The F-35 appears to be a trimmer single-engine version of the twin-engine F-22. The exhaust duct design was inspired^{[verification needed]} by the General Dynamics Model 200, a 1972 VTOL aircraft designed for the Sea Control Ship.^[5] In June 1994, Lockheed revealed that it had entered into a collaborative relationship with the Yakovlev Design Bureau on their bid for the Joint Advanced Strike Technology competition, consisting of the purchase of design data from the Russian company; according to Jane's All the World's Aircraft 2000-2001 this was data from the cancelled Yak-141 program which employed a similar propulsion system.^[6][7][8][9]
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 head-up display altogether.^[10]

Variants

X-35A (tail number 301)

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-22. 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 National Air and Space Museum Steven F. Udvar-Hazy Center, near Washington Dulles International Airport in Virginia.

X-35B (tail number 301)

The F-35B STOVL aircraft is intended to replace the Harrier, which was the world's first operational vertical/short takeoff and landing military jet. 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.
Instead of lift engines or rotating nozzles on the engine fan like the Harrier, the F-35B uses an innovative shaft-driven Lift Fan, patented by Lockheed Martin employee Paul Bevilaqua,^[11] and developed by Rolls-Royce.^[12] 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.^[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.
Arguably the most persuasive demonstration of the X-35's capability was the final qualifying Joint Strike Fighter flight trials on 20 July 2001, in which the X-35B STOVL aircraft took off in less than 500 feet (150 m), went supersonic, and landed vertically.^[14][15]

X-35C (tail number 300)

X-35C

The Naval F-35C variant will replace the F/A-18A, -B, -C, and -D Hornets, which replaced subsonic but long-range 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.^[16]
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.

Specifications (F-35)

Some information is estimated.

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

Data from Lockheed Martin^[17]

General characteristics

• Crew: 1
• Length: 50 ft 6 in (15.37 m)
• Wingspan: 35 ft 0 in (10.65 m)
• Height: 17 ft 4 in (5.28 m)
• Wing area: 459.6 ft² (42.7 m²)
• Empty weight: 26,000 lb (11,793 kg)
• Loaded weight: 44,400 lb (19,960 kg)
• Max takeoff weight: 60,000 lb (27,220 kg)
• Powerplant: 1× Pratt & Whitney F135 afterburning turbofan coupled to Rolls-Royce Lift System to give 18,000 lbf (80 kN) lift thrust
  • Dry thrust: 28,000 lbf (128 kN)
  • Thrust with afterburner: 43,000 lbf (191 kN)

Performance

• Maximum speed: Mach 1.6 (1,200 mph, 1930 km/h)
• Range: ~1,200 nmi (~2,222 km) on internal fuel
• Rate of climb: classified ()
• Wing loading: 91.4 lb/ft² (446 kg/m²)
• Thrust/weight: 0.968 with full fuel, 1.22 with 50% fuel

Gallery

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  X-35 flight, video of transition to VTOL configuration, hover, take off in STOVL configuration, in-flight re-fuelling, vertical hover and landing
  
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  Vertical landing (video)