Main Role: Multi-role Fighter/Attack aircraft

Country of Origin: USA           Current Status: Technology Demonstrator

In aiming to use advanced technology to provide a leap forward in operational fighter capability and at the same time substantially reduce manufacturing costs, the Joint Strike Fighter (JSF) programme has ambitious goals. For the winning design the rewards could be enormous. A potential market for 5,000-8,000 aircraft has been forecast.

The origins of JSF lie in the realisation by the US Marine Corps and Royal Navy during the 1980s that a replacement for the Sea Harrier and AV-8B would be required after the year 2000. Various research studies were undertaken on both sides of the Atlantic into advanced Short Take-Off and Vertical Landing (STOVL) concepts. The best of these concepts appeared to involve the use of a dedicated lift-fan located behind the cockpit. In 1989, DARPA (Defense Advanced Research Projects Agency) took over leadership of the advanced STOVL project and focused the on-going effort into a phased development programme leading to a flying demonstrator aircraft using the powerful new engines developed for the YF-22 and YF-23 Advanced Tactical Fighter.

As the studies progressed, it was realised that a STOVL aircraft with the lift-fan removed and replaced by a large fuel tank would result in a fighter with excellent long range capability. Such a fighter would fulfil the needs of the USAF, which was looking for a longer-ranged fighter capability in the light of Gulf War operations. Thus was born the Common Affordable Lightweight Fighter (CALF) project - aimed at producing a single aircraft design with both STOVL and Conventional Take-Off and Landing (CTOL) variants.

In March 1993, study contracts were issued to Lockheed and McDonnell Douglas under the CALF project. In addition, Boeing and Northrop Grumman initiated self-funded design studies. In 1995, CALF was absorbed into the Joint Advanced Strike Technology (JAST) programme, which was originally intended to focus on technology studies and demonstration of various equipment for next generation strike aircraft. In fact, JAST soon evolved into a firm requirement for an advanced single-seat, single-engined lightweight multi-role fighter which could be operated by the USAF, US Navy and US Marines in closely similar variants. The opportunity to replace the F-16, A-10, F/A-18C/D and AV-8B with one design would result in huge savings in costs due to the large production run. During 1996 JAST was renamed JSF (Joint Strike Fighter).

In November 1996, Boeing and Lockheed Martin were awarded contracts to build two Concept Demonstrator Aircraft (CDA) - one CTOL version and one STOVL version - each. The aircraft were not intended to be fighter prototypes, but rather to prove that the selected design concepts would work, hence the use of X-series designations. The Boeing design received the designation X-32 and the Lockheed Martin design the designation X-35.

The design of the Lockheed Martin X-35 is clearly derived from that of the F-22 Raptor. The aerodynamic configuration is very similar, as is the application of stealth technology in the shaping of the fuselage. The STOVL version features a Rolls-Royce (Allison) designed lift-fan located behind the cockpit. The fan is mechanically driven by a shaft running from the engine and is designed to support almost half of the aircraft's weight when in the hover. At the rear of the fuselage is a pitch-axis vectoring nozzle for the engine exhaust, which provides the remaining thrust to balance the aircraft.

For the two CDA aircraft, the designation X-35A was allocated to the CTOL version and X-35B to the STOVL version. Unlike Boeing, Lockheed Martin introduced a third version, the X-35C, to undertake simulated aircraft carrier (CV/CTOL) testing. This aircraft was produced by converting the X-35A after it had completed it's planned flight trials. The X-35A and X-35B have very similar airframes, including the aft cockpit bulge and associated doors for the lift-fan, which is only fitted to the X-35B. In addition to the clamshell doors above and below the lift-fan bay are another set of doors in the aircraft spine serving an engine auxiliary intake for use at low forward speeds. When transitioning to and from the hover, all three sets of doors open or close as required. The X-35C was converted at Palmdale from the X-35A. It featured increased wing area and significantly larger tail surfaces to demonstrate carrier approach performance.

The production version of the X-35, known as the Preferred Weapons System Concept (PWSC), will feature a number of design changes. All versions will have the main air intakes reshaped and located further aft on the fuselage. The USAF's CTOL version is considered the baseline model. The STOVL version is 81% common in terms of airframe structure, while the CV version is only 62% common. The CTOL and STOVL versions have the same wing design, which has increased area compared to the X-35A/B. The CV version has much larger wings and tail surfaces and strengthened landing gear, including a twin wheel noseleg. The CTOL and CV versions will not feature the slightly bulged area behind the cockpit, which houses the lift-fan on the STOVL version, allowing a larger canopy glazed area. Extra fuel will be accommodated in place of the lift fan. The CTOL and CV versions will also feature slightly bulged weapons bay doors to accommodate larger weapons.

The Lockheed Martin X-35 was selected as the winning JSF design on 26 October 2001.

X-35A CTOL Demonstrator	Front View of X-35A	X-35A Taxi-ing

Variants

Requirement Specification: JORD - Joint Operational Requirements Document

Manufacturers Designation: Model 220

Development History:

X-35A                    CTOL concept demonstrator for the USAF. Configuration 220A.
X-35B                    STOVL concept demonstrator for the USMC and Royal Navy. Configuration 220B.
X-35C                    CV/CTOL concept demonstrator for the US Navy. Converted from X-35A. Configuration 220C.
Model 235             Lockheed Martin designation for PWSC production version.
CTOL PWSC          Baseline production version, for USAF.
STOVL PWSC       USMC production version with lift fan in bulged area aft of cockpit, shorter cockpit canopy and no bulging of weapons bay doors.
CV PWSC               US Navy production version, featuring much larger wing and tail surfaces and strengthened landing gear with twin wheel noseleg.

History

Key Dates:

• 1990 Common Affordable Lighweight Fighter (CALF) study launched by Defense Advanced Research Project Agency (DARPA).
• August 1994 United Kingdom joins study programme.
• 1995 CALF incorporated into JAST (Joint Advanced Strike Technology) concept studies.
• March 1996 Request for proposals issued to Boeing, Lockheed Martin and McDonnell Douglas led teams.
• Mid 1996 JAST programme renamed JSF (Joint Strike Fighter).
• 16 November 1996 McDonnell Douglas eliminated from competition. Lockheed Martin and Boeing awarded contracts to produce and flight test 2 technology demonstrators each.
• 1997 Northrop Grumman and British Aerospace join Lockheed Martin team.
• 24 October 2000 Maiden flight of X-35A CTOL demonstrator.
• 21 November 2000 First supersonic flight of X-35A.
• 16 December 2000 Maiden flight of X-35C CV/CTOL demonstrator.
• February 2001 Final production PWSC design submitted.
• 24 June 2001 First hover of X-35A converted to X-35B STOVL demonstrator configuration.
• 20 July 2001 X-35B demonstrates short take-off, level supersonic dash and vertical landing in one flight.
• 26 October 2001 Lockheed Martin X-35 wins the JSF competition. Engineering Manufacturing Development (EMD) contract to be awarded in November.
• 2005 Projected maiden flight of first EMD aircraft
• 2008 Projected in-service date for CTOL aircraft.
• 2008 Projected in-service date for STOVL aircraft.
  

X-35B over Hoverpit	X-35B with Intake Doors open	X-35B cruising at Altitude

Operators

Military Operators

U.S. Air Force                              (1,763 planned)
U.S. Navy                                     (480 planned)
U.S. Marine Corps                        (609 planned)
UK - Royal Navy                           (60 planned)
Government Agencies
None
Civilian Operators
None

Specifications

Crew: Pilot.

Dimensions: Length 50 ft 11 in (15.52 m); Height ? ft ? in (? m); Wing Span 40 ft 0 in (12.19 m) for X-35C, 33 ft 0 in (10.05 m) for X-35A/B; Wing Area 600 sq ft (55.7 sq m) for X-35C, 412.3 sq ft (38.3 sq m) for X-35A/B

Engines: One Pratt & Whitney F119-PW turbofan derivative, designated SE611, of 42,000 lb. (186.9 kN) st. with afterburning plus Rolls-Royce lift fan (X-35B only) of 18,000 lb (80 kN) thrust. (F119-PW-611C for CV/CTOL and F119-PW-611S for STOVL variant).

Weights: Empty Operating 25,000 lb (11,340 kg); Maximum Take-off 50,000 lb (22,680 kg)

Armament: Six AIM-120C AMRAAM or two AIM-120C AMRAAM and two 2,000 lb. JDAM in internal fusleage bay; provision for one 20mm M61A2 rotary cannon with 400 rounds in starboard wing root (USAF CTOL variant). Provision for 4 underwing pylons with 5,000 lb (2,268 kg) capacity each.

Performance: Maximum level speed Mach 1.4+ at altitude; Maximum rate of climb at sea level classified; Service ceiling 50,000+ ft (15,240+ m); Radius of action 540 nm (622 miles, 1000 km) for USMC attack mission, 600 nm (691 miles, 1112 km) for US Navy attack mission

Top view of X-35 C	X-35C Rear View	X-35C Cruising