TYPE: Multirole fighter.

PROGRAMME: Origins of Joint Strike Fighter (JSF) programme vested in separate USAF/USN Joint Advanced Strike Technology (JAST) and Defense Advanced Research Project Agency (DARPA) Common Affordable Lightweight Fighter (CALF) projects of early 1990s.
Projects merged in November 1994, as JAST, after Congressional directive in mid-1994; programme renamed JSF in latter half of 1995. Previously, formal request for proposals (RFP) for preliminary research contracts released on 2 September 1994, stipulating industry response by 4 November and issue of contract awards by 16 December.
Some elements of US industry joined forces to win JAST/JSF work, with international collaboration in evidence. McDonnell Douglas led one team after signing October 1994 Memorandum of Understanding (MoU) with Northrop Grumman and British Aerospace; each company submitted individual bids, but all three would participate in event of securing contract. Boeing allied with Dassault of France on aspects of subsystem design effort.
Subsequent research contracts worth US$99.8 million were distributed between four companies: Boeing (US$27.6 million), Lockheed Martin (US$19.9 million), McDonnell Douglas (US$28.2 million) and Northrop Grumman (US$24.1 million). Further US$28 million allocated for associated avionics, propulsion systems, structures and materials, and modelling and simulation.
Merger of JAST and CALF resulted in expanded flight test programme, involving two finalists; each to build two demonstrators, one with ASTOVL capability and the other to use conventional take-off and landing (CTOL).
Draft RFP issued December 1995, with USA and UK signing MoU on 20 December 1995, which committed UK to participate in four year weapons system concept demonstration (WSCD) phase. MoU also stipulated that UK must contribute some 10 per cent (approximately US$200 million) of demonstration phase costs as full collaborative partner.
Formal release of the final RFP for JSF was expected on 7 March 1996, but was delayed to June 1996, with contract award date in November 1996.
All WSCD contenders chose Pratt & Whitney's F119 (later redesignated F135) engine for their proposals, although a General Electric/Allison/Rolls-Royce team secured a US$7 million contract in March 1996 to examine alternative power plants. These were based on the General Electric F110 and YF120 engines, with the latter being chosen in May 1996 following Congressional directive aimed at fostering competition and also overcoming possible impact of developmental or operational problems with the F119. Further US$96 million multiyear contract awarded in February 1997 to cover technology maturation and core engine development of alternate F136 engine over four-year period. Original intent was to begin full-scale EMD of F136 in about 2004, but US$511 million cut in funding during FY04 to FY09 expected to result in two-year delay, with production engine not now likely to be available until 2013, at earliest.
On 16 November 1996, US Secretary of Defense, William J Perry announced that Boeing and Lockheed Martin had been chosen to participate in WSCD. Simultaneously, Boeing was awarded a US$661.8 million contract for the X-32, while Lockheed Martin received US$718.8 million for the X-35; in addition, Pratt & Whitney secured a contract worth US$804 million for the associated Engine Ground and Flight Demonstration Program. Subsequently, Northrop Grumman and British Aerospace joined Lockheed Martin team.
Australia, Canada, France, Germany, Greece, Israel, Singapore, Spain and Sweden were all briefed on JSF programme. For System Development and Demonstration (SDD) phase, four partnership options available. Most costly is Level 1, with responsibility for 10 per cent of cost; UK is only partner at this level. Italy and the Netherlands are Level 2 partners, each contributing about 5 per cent of cost. Level 3 involves payment of 1 to 2 per cent, with Denmark and Norway having teamed up to share burden, while Australia, Canada and Turkey meet the cost alone. Finally, Security Cooperation Participant Level involves smaller contribution of US$75 million; Israel and Singapore were first two subscribers, signing letters of intent in February 2003. Greece, Poland and South Korea are potential future additions and Taiwan may also acquire STOVL version in due course.
Lockheed Martin development included production of 91 per cent scale powered model of JAST demonstrator for wind-tunnel tests. Model JAST, with F100 engine, began trials at Pratt & Whitney's West Palm Beach, Florida, facility in February 1995; subsequently to outdoor hover test rig at NASA Ames and then installed in 24 x 36 m wind tunnel at Mountain View, California, for series of powered hover and transition tests which ran from December 1995 to 5 March 1996; total of 196 hours accumulated, representative of approximately 2,400 take-offs and landings with the vertical lift system. Midway through outdoor hover tests, design was reconfigured to eliminate canards.
Lockheed Martin design, development, construction and flight testing of full-scale demonstrator aircraft, required one initially to be flown as CTOL version (X-35A) to demonstrate land-based USAF model, before being reconfigured to serve as STOVL version (X-35B) for US Marine Corps, Royal Air Force and Royal Navy; other aircraft representative of carrier-capable US Navy model (X-35C). Although Fort Worth is team leader, both X-35 aircraft built at Palmdale, California, using rapid prototyping techniques.
Design of X-35 frozen as Configuration 220 13 June 1997 after Initial Design Review, at which time 11,000 hours of model testing accumulated. Development team joined by Northrop Grumman on 8 May 1997 and BAe (later BAE Systems) on 18 June 1997.
Release of engineering drawings in early September 1997 heralded start of parts production at Palmdale for demonstrator aircraft; by end of 1997, Lockheed Martin had completed about 70 per cent of required tooling and had conducted second interim programme review. X-35 final design review completed in September 1998 and coincided with roll-out of full-scale mockup at Fort Worth. Assembly of first aircraft began in April 1998, with main wing carry-through bulkhead installed in early August 1998, by which time manufacturing of large composites skins for upper and lower wing surfaces also complete; aircraft moved from assembly testing to factory floor on 18 September 1999, in readiness for installation of flight control surfaces and landing gear as well as systems checks.
Flight control system software tested on NF-16D VISTA in 1998 as part of integrated subsystem technology demonstration. Further trials using AFTI/F-16 in 1999-2000 involved all-electric flight control system and modular electric power system planned for JSF. JSF avionics also tested on Northrop Grumman's BAe One-Eleven Cooperative Avionics Test Bed (CATB), which was fitted with sensors, processors and software in 1999; trials begun of Northrop Grumman radar and distributed infra-red sensor system, Kaiser helmet-mounted display and Lockheed Martin core processor in first quarter 2000.
More than 100 hours of flight time accumulated by early September 2000 using CATB, when avionics development and integration process completed; successful demonstrations included automatic target cueing (ATC), whereby sensors acquire targets rapidly and automatically; electro-optical targeting system (EOTS); electronic warfare suite and electronically scanned radar. Subsequent testing included co-operative engagement between CATB and Northrop Grumman E-8C Joint STARS, demonstrating all-weather precision targeting and combat identification techniques for fixed and moving targets.
Design of JSF continued to be refined after selection of Configuration 230-1. By 1998, third version of Configuration 230 (230-3) had reduced area of USAF/USMC JSF wings by seven per cent, but increased USN variant's wing area by 11 per cent. Further redesign occurred in 1999, culminating in September with Configuration 230-5, which has enlarged wing to satisfy sustained turn performance requirement and strengthened to meet 9 g stress requirement for the CTOL variant; further main change involved redesign of lift-fan nozzle from D-shape extendible box to venetian blind-type box, offering dual benefits of simpler design and reduced weight for the STOVL configuration.
Redesign process continued into 2000, with Configuration 230-5 adding further refinements aimed at reducing weight and increasing payload bringback capability; resultant structural modification entailed weight reduction in several areas such as weapon bay and landing gear door assemblies. Configuration 230-5 finally submitted as Preferred Weapons System Concept design in mid-2000.
Significant programme events in latter part of 1998 and 1999 included first test run of basic Pratt & Whitney JSF119 engine (designated FX661) at West Palm Beach, Florida, facility on 11 June 1998; over 330 hours of developmental testing performed by end August 1999, validating complete X-35 flight envelope. Final altitude flight qualification testing undertaken with another engine (designated FX663) in fourth quarter of 1999. National Aerospace Laboratory low-speed wind tunnel in the Netherlands used for testing of scale models of JSF starting in June 1998; initial trials of lift fan system's clutch, fan and gearbox rigs at Indianapolis, Indiana, in May and June 1998; and installation of engine inlet duct in assembly tool at Palmdale at beginning of July 1998. Subsequently, also in July, over 50 hours of preliminary engine testing were completed at West Palm Beach, including vibration surveys, fan and core running-in, operating performance calibration and engine control stability assessment; next key phase of engine test programme involved altitude testing at Arnold Engine Development Center, Tennesse.
Testing of first STOVL engine (designated FX662) undertaken initially at West Palm Beach; first run with lift fan engaged accomplished on 10 November 1998, with operation to 100 per cent speed following on 22 November; first series of tests included stress surveys and performance calibration and occupied about six weeks. Validation of STOVL propulsion system achieved in late August 1999, with high-power clutch engagement of shaft-driven lift fan, simulating seamless conversion from conventional wing-borne flight configuration to jet-borne flight configuration for STOVL approach ending with vertical landing.
Following this, on 9 December 1999, flight engine YF001 successfully installed on the X-35A demonstrator at Palmdale, with integration tests, including plumbing connections, data communications and electrical checks, beginning immediately thereafter.
In UK, DERA vectored-thrust advanced aircraft control (VAAC) Harrier T.Mk 4 completed 20 hour, 36 sortie, flight test programme in November 1998, during which a sidestick control column was evaluated by civilian and military pilots. Two-phase programme began with initial calibration to validate STOVL control laws and stick characteristics; subsequent evaluation included pattern work, approach and transition to hover and precision and aggressive hover tasks, resulting in confirmation that side-stick provides satisfactory control of STOVL aircraft at low speeds.
Lockheed Martin also reached preliminary agreement with partners over word-sharing arrangements to be implemented for large-scale production. Lockheed Martin has responsibility for forward fuselage, cockpit, wing edges and final assembly; Northrop Grumman to fabricate mid-fuselage and wing box, with BAE Systems producing tails and aft fuselage section.
Radar signature testing of full-scale pole model began in late 1999 at Helendale, California; this included measurement of radar cross-section, assessment of antenna performance and demonstration of the robustness of supportable low-observable materials.
Significant events in 2000 included X-35A flight readiness review in March. Subsequently, in April, testing associated with development and flight qualification of the JSF119-PW-611 engine for the X-35A and X-35C was completed after 193 hours of operating time. Final assembly and painting of X-35A in late May was followed by lengthy series of ground tests, including systems checkout, engine running at full military power and with full afterburner augmentation, and low- and medium-speed taxi tests. These extended into October and culminated in a successful first flight by X-35A Article 301 from Palmdale to Edwards on 24 October; by 6 November, further four flights had been made, including first by USAF pilot, and envelope had been expanded to 390 kt (722 km/h; 449 mph); first aerial refuelling (from KC-135) on 7 November; maiden supersonic flight 21 November, when 25 hours had been flown in 25 sorties. X-35A test programme completed on 22 November, whereupon Article 301 returned to Palmdale for conversion to X-35B. X-35C (Article 300) first flight took place on 16 December 2000 from Palmdale to Edwards AFB. Initial X-35C testing at Edwards was completed in early February 2001, with aircraft making transcontinental ferry flight via Fort Worth, Texas, to Navy test centre at Patuxent River, Maryland on 9-10 February for specialised trials.
Following installation of shaft-driven lift fan in late December 2000, X-35B STOVL version began series of hover-pit trials on 22 February 2001; these concluded 16 March and included 26 lift-fan clutch engagements from CTOL to STOVL mode at high rpm settings. Accelerated mission testing followed and was concluded on 6 April, with X-35B then being readied for flight trials; this process included installation of flight-ready lift fan. Taxi tests began 12 June 2001, followed by first brief vertical take-off and landing on 23 June, with sustained hover accomplished on next day. Initial testing at Palmdale completed successfully by 3 July, when X-35B flown to Edwards AFB for remainder of trials programme; notable events included first airborne transition from STOVL to conventional mode on 9 July; first vertical landing from wingborne flight on 16 July and 'Mission X' demonstrations involving short take-off, level supersonic dash and vertical landing on 20 and 26 July, before STOVL testing concluded on 30 July.
Both X-35 aircraft subsequently allocated to museums, with Article 300 going to the naval air museum at Patuxent River and Article 301 joining the Smithsonian collection in Washington, DC.
After study of test results and company proposals, the US Department of Defense announced on 26 October 2001 that Lockheed Martin would be awarded a US$19 billion contract to cover SDD of what now became known as the F-35. Scheduled to occupy 126 months, SDD began immediately. Simultaneously, it was revealed that Pratt & Whitney would receive a contract worth US$4 billion for development and production of the associated F135 engine. As a major partner, the UK will contribute US$2 billion towards total SDD expenditures of approximately US$30 billion. Majority of preliminary design review successfully concluded on 27 March 2003, with a few unresolved items concerning aircraft weight and weapons integration not finally resolved until end of June; next major hurdle is critical design review, scheduled for April 2004.
A total of 14 fully instrumented flying aircraft will be built at Fort Worth and assigned to SDD. Five will emerge as F-35As (USAF CTOL version); five will be F-35Cs (US Navy CV version); and the remaining four will be F-35Bs (US Marine Corps/UK STOVL version). Further eight non-flying airframes: two of each version as static test articles, plus another F-35C for drop testing and one pole-test airframe for radar signature evaluation. F-35A first flight scheduled for October 2005, 48 months into SDD, although Lockheed Martin is aiming for maiden flight on 28 August 2005. Just over 40 per cent of total planned flight testing by all JSF variants to be undertaken by F-35A, F-35B to fly after 53 months (making first vertical 'press-up' early 2006); and F-35C after 62 months (October 2006). Flight trials will be undertaken by Lockheed Martin at Fort Worth as well as joint industry/service teams at Edwards AFB, California (USAF) and NAS Patuxent River, Maryland (US Navy). Programme originally expected to involve almost 15,000 flight hours, although this reduced to 10,185 (about 5,700 sorties) according to most recent estimates.
Full funding for Low-Rate Initial Production (LRIP) is scheduled to begin in FY06, with the first delivery of an operational aircraft (an F-35A for the USAF) due in late 2008. F-35B will be first to attain IOC, in last quarter of FY10. Respective IOC dates for the F-35A and F-35C are final quarter of FY11 and final quarter of FY12, with the UK also expected to achieve IOC in FY12. Initial aircraft will be to Block 1 standard, with basic warfighting capability (including compatibility with JDAM and AIM-120 AMRAAM); additional weaponry for enhanced air-to-air, SEAD, close air support and interdiction will be added on Block 2 standard aircraft, while Block 3 will introduce more missiles and bombs and add deep strike capability. Lockheed Martin anticipates production rate of 17 aircraft per month at Fort Worth from 2011, but would like to achieve rate of 22 per month. With peak demand likely to be for about 30 a month, this could only be accomplished with second production centre. In early 2003, UK government commissioned Rand to perform feasibility study into creating second assembly line in UK.

CURRENT VERSIONS: Three variants of basic design, optimised for the mission requirements of different armed services. As currently envisaged, basic company designation for operational JSF is Configuration 240-1, with following variants expected to enter service with US armed forces.
F-35A: Land-based CTOL derivative for USAF. Evaluated by X-35A between 24 October and 22 November 2000.
F-35B: STOVL version for US Marine Corps, Royal Air Force and Royal Navy. Engine-driven lifting fan behind cockpit replaces some fuel. Wing folding originally specified on Royal Navy version only, but requirement since dropped. Broader and higher spine behind cockpit to accommodate lifting fan and air intake; shortened cockpit canopy replaces blister-type glazing of F-35A and B. Evaluated by X-35B between 23 June and 30 July 2001; final flight on 6 August 2001 was from Edwards AFB to Lockheed Martin facility at Palmdale.
F-35C: Carrier-based CTOL (CV). Wing, fin and elevator areas increased by chord extension; ailerons in addition to flaperons on wing; enlarged control surfaces and modified control system; strengthened landing gear with catapult launch bar on twin-wheel nose leg; concealed arrester hook; and folding wing. Evaluated by X-35C between 16 December 2000 and 10 March 2001 from test centres at Edwards AFB and Patuxent River, Maryland (from 10 February 2001).
EA-35B: Lockheed Martin studies into potential two-seat electronic attack version that could replace Marine Corps EA-6B from about 2015. Would retain internal weapons carriage capability, with sensors and jamming equipment embedded in fuselage and wings.

CUSTOMERS: Two X-35 demonstrators; initial planning called for some 3,000 F-35s for USA and UK, but US Navy and Marine Corps requirement cut significantly in 2003. UK confirmed on 30 September 2002 that F-35B (STOVL) version will be procured for both RAF and Royal Navy, with service introduction during 2012. Orders also expected from Australia (up to 100, possibly including some configured for long-range surveillance and reconnaissance), Canada, Denmark, Israel, Italy, Netherlands, Norway, Singapore and Turkey.

COSTS: At time of down select for SDD phase, unit cost of USAF F-35A quoted as US$37.3 million, with CV/STOVL versions costing under US$50 million each, US$3.41 billion SDD funding for FY03, following US$1.52 billion appropriation in FY02; requests for FY04 and FY05 are US$4.37 billion and US$4.47 billion respectively. Fly away costs mentioned in connection with Italian involvement quoted as US$36.6 million for CTOL version, US$47.4 million for CV version and US$45.3 million for STOVL version. UK purchase of 150 F-35Bs estimated to cost around UK £10 billion.

DESIGN FEATURES: Trapezoidal mid-wing configuration, optimised for low observability. Twin tailfins; internal weapon bays. Wing and tailplane leading-edges swept back approximately 33°; trailing-edges swept forward approximately 14°; fins swept back approximately 42° and canted outward at tips by approximately 25°. Twin 'divertless' fibre-placed graphite/epoxy composites engine air intakes with no moving parts produced by ATK. All-electric flight control system.
STOVL version employs a lifting fan behind the cockpit, driven by a shaft from the single engine; inlet and outlet are covered by doors, except when in use; original side-hinged bi-fold hatch of X-35B replaced in early 2003 by single-piece cantilever inlet door hinged at rear. Other changes related to thermal management also incorporated at this time, to satisfy requirement to operate on 49°C (120°F) day. The resultant cold air barrier prevents hot air from being reingested when on or near the ground.

FLYING CONTROLS: All-electric flight control system for movement of primary flight control surfaces (flaps, tailerons and rudder) incorporating Parker Hannifin electrohydrostatic actuators. Moog leading-edge flap drive system. Flight control computer originally to be supplied by Honeywell, but replaced by advanced Lockheed Martin unit in third quarter of 1998 to eliminate anticipated throughput problems arising from growth in flight control software.

LANDING GEAR: Retractable tricycle type; mainwheels retract inwards; nosewheel(s) forward. Single wheels on each unit, except twin nosewheels and catapult towbar on F-35C, which also has reinforced gear for deck landings. Tyres will feature embedded transponder including integrated circuit and capacitive pressure sensor to facilitate monitoring of pressure and condition. Dunlop selected to provide 34 x 11.OR16 radial main tyres for SDD phase of STOVL F-35B version; Honeywell to develop wheels and brakes, with Crane Hydro-Aire supplying brake control and anti-skid system.

POWER PLANT: One 178kN (40,000 lb) class (111 kN; 25,000 lb st dry thrust) Pratt & Whitney F135 (formerly JSF119-PW-611; F119 derivative) turbofan. Rolls-Royce three-bearing swivel-duct nozzle on -611S version to deflect thrust downwards for STOVL, plus a Rolls-Royce engine-driven fan behind cockpit and a bleed air reaction control valve in each wingroot to provide stability at low speeds. For F-35B, total vertical lift of 177 kN (39,700 lb st) comprises some 40 per cent from main nozzle, 48 per cent from fan and 12 per cent from reaction control valves. F-35A has in-flight refuelling receptacle on spine; US Navy and Marine Corps require retractable probe on starboard side. JP-5 or JP-8 fuel. General Electric/Rolls-Royce F136 turbofan with same performance characteristics under development as alternative powerplant.

ACCOMMODATION: Pilot only; canopy by Sierracin; canopy frame assembly by Smiths Aerospace. STOVL versions have canopy of reduced length. Martin-Baker Mk 16E lightweight ejection seat in X-35s; F-35 expected to have new seat resulting from Joint Ejection Seat Program (JESP).

SYSTEMS: Hamilton Sundstrand 80 kW engine-driven switched-reluctance starter/generator providing two independent channels of 270 V DC electrical power; electric distribution units, power panels, power distribution centres, batteries and battery charger equipment provided by Smiths Industries; electrical wiring on SDD aircraft by Stork Aerospace of the Netherlands; Honeywell thermal- and energy-management module (T/EMM) combining functions of auxiliary and emergency power units and environmental control system; 270 V DC lithium ion emergency battery. Weapons bay door drive system by TRW Aeronautical Systems.

AVIONICS: Comms: TRW to provide next-generation CNI (communications, navigation and identification) avionics for F-35; package will include VHF/UHF radio, Have Quick I/II, SINCGARS/SIP, SatCom, IFF/SIF transponder, ILS, MLS, ACLS, Tacan. infra-flight data link, Link 4A, Link 16/JTIDS and weapons data link.
Radar: Northrop Grumman MIRFS/MFA (multifunction integrated RF system/multifunction nose array) combines active electronically scanned array (AESA) radar, electronic warfare and communications functions planned for production F-35.
Flight: Lockheed Martin Tactical Defense Systems Integrated Core Processor (ICP) incorporating open system architecture.
Instrumentation: Kaiser 200 x 500 mm (8 x 20 in) single flat panel MFD. Meggitt secondary flight display system. Kaiser/Vision Systems International selected in third quarter of 1999 to provide advanced integrated helmet-mounted display system.
Mission: Northrop Grumman conformal array multifunction imaging IR sensor system under development for JSF; electro-optical distributed aperture system (EODAS) functions include air-to-air search-and-track, target cueing and missile warning, and air-to-ground surface-target tracking; uses six CMC Electronics conformal compact lightweight imaging IR sensors around airframe and seventh in targeting system pod, with combined data providing all-aspect multifunction imaging to pilot via wide-angle helmet-mounted display, overlaid with target and threat data information. Lockheed Martin internal Electro-Optical Targeting System (EOTS) can be used when engaging targets on the ground and in the air.
Self-defence: EW capability incorporated into MIRFS/MFA. BAE Systems is prime contractor for EW equipment and systems integration; Litton Amecom to supply low-cost ESM equipment.

ARMAMENT: Internal cannon (in port engine air intake trunk upper surface) specified by USAF and under consideration by US Navy; Boeing/Mauser BK 27 originally selected, but replaced by General Dynamics GAU-12 25 mm weapon in fourth quarter of 2002. US Marine Corps and UK variants to have 'missionised' 25 mm cannon in low-observables pod. Internal weapon bays, incorporating pneumatic weapon suspension and release equipment by EDO; USAF, USN and USMC weapons fit is two AIM-120C AMRAAMs and two GBU-31 JDAM bombs. Other weapons expected to be used by the F-35 include CBU-105 WCMD Sensor Fuzed Weapon, GBU-12 Paveway II, AGM-154 JSOW, AIM-132 ASRAAM and GBU-32 JDAM, all for internal carriage; externally carried weapons are expected to include AGM-158 JASSM, Storm Shadow cruise missile and the AIM-9X Sidewinder. Optional external stores on four hardpoints, which can accommodate fuel tanks or up to 6,800 kg (15,000 lb) additional ordnance.