F-35 Lightning II joint strike fighter (JSF) is a stealthy, supersonic multirole fighter developed by Lockheed Martin Aeronautics Company for the US Air Force, Navy and Marine Corps and programme partners from the North Atlantic Treaty Organization (Nato) and US allies.
The single-seat fighter was designated the F-35 Lightning II in July 2006. The JSF is available in three variants: F-35A, a conventional take-off and landing aircraft (CTOL); F-35B, a short take-off and vertical landing (STOVL) aircraft; and F-35C, a carrier variant (CV). A 70%-90% commonality is required for all variants.
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The USAF has a planned purchase programme of 1,763 F-35A air-to-ground strike aircraft to replace F-16 fighter aircraft and A-10, complementing F-22 aircraft. The USMC will acquire 353 F-35B STOVL jets and 67 F-35C CV aircraft to replace F/A-18B/C and AV-8B, while the US Navy plans to procure 260 F-35C jets to replace F/A-18B/C and A-6, complementing the F/A-18E/F. Together, the UK Royal Air Force and Royal Navy intend to operate a total of 138 F-35B jets.
More than 570 F-35 aircrafts were delivered by October 2020.
Lightning II Joint Strike Fighter (JSF) development
The Lockheed Martin JSF team includes Northrop Grumman, BAE Systems, Pratt and Whitney and Rolls-Royce. Final assembly of the aircraft took place at Lockheed Martin’s Fort Worth plant in Texas.
Major subassemblies were produced by Northrop Grumman Integrated Systems at El Segundo, California and BAE Systems at Samlesbury, Lancashire, England. BAE Systems is responsible for the design and integration of the aft fuselage, horizontal and vertical tails and the wing-fold mechanism for the CV variant, using experience from the Harrier STOVL programme. Terma of
Denmark and Turkish Aerospace Industries of Turkey are supplying sub-assemblies for the centre fuselage.
In January 2001, the UK MoD signed a memorandum of understanding to co-operate in the SDD (system development and demonstration) phase of JSF and, in September 2002, selected the STOVL variant to fulfil the future joint combat aircraft (FJCA) requirement. Following the contract award, other nations signed up to the SDD phase are: Australia, Canada, Denmark, Italy, Netherlands, Norway, Singapore and Turkey.
The development of the centre fuselage for the first international F-35 joint strike fighter began in October 2009. It was developed by Northrop Grumman, principally for the UK. The centre fuselage including composite air inlet ducts were supplied by Turkish Aerospace Industries (TAI).
The F-35B short take-off and vertical landing (STOVL) variant, designated BK-1, completed its assembly in November 2011. The variant was developed as part of the low-rate initial production (LRIP) 3 and its first flight took place in April 2012.
Training centre at Elgin Air Force Base and F-35 operational bases
An integrated training centre for the F-35 fighter programme was set up at Elgin Air Force Base in the US. The training centre was inaugurated in November 2010. The F-35 Lightning programme has eight pilot training bases – MCAS Beaufort, RAF Marham, Luke Air Force Base (AFB), Eglin AFB, Misawa Air Base, RAAF Base Williamtown, NAS Lemoore, and Cheongju Air Base. The aircraft also flies at Nevatim Air Base, NAS Patuxent River, MCAS Iwakuni, Hill AFB, Edwards AFB, Amendola Air Base, and Nellis Air Force Base.
Concept demonstration phase led by Boeing and Lockheed
The concept demonstration phase of the programme began in November 1996 with the award of contracts to two consortia, led by Boeing Aerospace and Lockheed Martin. The contracts involved the building of demonstrator aircraft for three different configurations of JSF, with one of the two consortia to be selected for the development and manufacture of all three variants.
In October 2001, an international team led by Lockheed Martin was awarded the contract to build JSF. An initial 22 aircraft (13 flying test aircraft and eight ground-test aircraft) are built in the programme’s system development and demonstration (SDD) phase. Flight testing was carried out at Edwards Air Force Base, California, and Naval Air Station, Patuxent River, Maryland.
In April 2003, JSF completed a successful preliminary design review (PDR). The critical design review (CDR) for the F-35A was completed in February 2006, for the F-35B in October 2006 and for the F-35C in June 2007. The first flight of the CTOL F-35A took place in December 2006.
Low-rate initial production (LRIP) for the F-35A/B was approved in April 2007 with an order for two CTOL aircraft. An LRIP 2 contract for six CTOL aircraft was placed in July 2007. The STOVL F-35B was rolled out in December 2007 and made its first flight, a conventional take-off and landing, in June 2008. STOVL flights began in early 2009. An LRIP contract for six F-35B
STOVL aircraft was placed in July 2008. The F-35C took off on its first flight in November 2011.
Agreements with participating nations
By the end of 2006, Australia, Canada, the Netherlands and the UK had signed the MoU for the F-35 Production, Sustainment and Follow-on Development (PSFD) phase.
Norway and Turkey (requirement 100 F-35A) signed in January 2007, while Denmark and Italy (requirement 131 F-35A and B) signed in February 2007.
Participating nations were to sign up to the initial operation test and evaluation (IOT&E) phase by the end of February 2009. In October 2008, Italy announced that it intended not to participate in the IOT&E.
The US and the UK are tier one partners in the F-35 JSF programme. Italy and The Netherlands are tier two partners, while Denmark, Norway, Turkey, Australia, and Canada are tier three partners.
Orders and deliveries
The USAF ordered 32 new F-35A aircraft in 2010. USMC ordered 16 F-35B aircraft and is considering more 13 more aircraft. The USN ordered seven F-35Bs aircraft in 2009, and 12 F-35s were delivered to the US in 2011.
The UK ordered two F-35B’s in 2009 and one F-35C in 2010. The Netherlands ordered three F-35A aircraft, one in 2010 and two in 2011. Australia decided to purchase 14 F-35A aircraft in October 2010.
In May 2008, Israel requested the sale of 25 F-35A aircraft with 50 options. Israel ordered 20 F-35I variant aircraft in 2010 following the Israeli Government’s decision to select the F-35 as its next-generation aircraft. In June 2011, the Norwegian Parliament unanimously approved the funding of four F-35 Lightning II training jets to stabilise Norway’s future air-combat capability requirements.
Canada also announced its choice of F-35 aircraft for its future fighter requirements. The Italian Parliament has approved the purchase of 131 F-35 aircraft and construction of a final assembly facility at Cameri Air Base.
In October 2019, the US Department of Defense (DoD) reached an agreement worth $34bn with Lockheed Martin for the purchase of 478 additional F-35 aircraft across Lots 12-14. The deal covers the delivery of aircraft to the US and its partner nations.
Design differences between variants of the Joint Strike Fighter
In order to minimise the structural weight and complexity of assembly, the wingbox section integrates the wing and fuselage section into one piece. To minimise radar signature, sweep angles are identical for the leading and trailing edges of the wing and tail (planform alignment).
The fuselage and canopy have sloping sides. The seam of the canopy and the weapon bay doors are sawtoothed and the vertical tails are canted at an angle.
The marine variant of JSF is very similar to the air force variant, but with a slightly shorter range because some of the space used for fuel is used for the lift fan of the STOVL propulsion system.
The main differences between the naval variant and the other versions of JSF are associated with the carrier operations. The internal structure of the naval version is very strong to withstand the high loading of catapult-assisted launches and tailhook arrested landings.
The aircraft has larger wing and tail control surfaces for low-speed approaches for carrier landing. Larger leading edge flaps and foldable wingtip sections provide a larger wing area, which provides an increased range and payload capacity.
The canopy (supplied by GKN Aerospace), radar and most of the avionics are common to the three variants.
The centre fuselage assembling process includes loading of an all-composite air inlet duct into a special tooling structure called a jig, followed by 18 major steps such as bonding metal frames around the duct. The frames serve to brace and position the duct properly within the centre fuselage.
Cockpit and avionics systems
L-3 Display Systems, now part of L3Harris, has been developing the panoramic cockpit display system, which will include two 10in×8in active matrix liquid crystal displays and display management computer.
The following will also supply F-35 avionics systems:
· BAE Systems Avionics – side stick and throttle controls
· Vision Systems International (a partnership between Kaiser Electronics and Elbit of Israel) – advanced helmet-mounted display
· BAE Systems Platform Solutions – alternative design helmet-mounted display, based on the binocular helmet being developed for the Eurofighter Typhoon
· Ball Aerospace – communications, navigation and integration (CNI) integrated body antenna suite (one S-band, two UHF, two radar altimeter, three L-band antennas in each aircraft)
· Harris Corporation (now L3Harris) – advanced avionics systems, infrastructure, image processing, digital map software, fibre optics, high-speed communications links and part of the communications, navigation and information (CNI) system
· Honeywell – radar altimeter, inertial navigation / global positioning system (INS/GPS) and air data transducers
· Raytheon – 24-channel GPS with digital anti-jam receiver (DAR).
Weapons and armaments
Weapons are carried in two parallel bays located in front of the landing gear. Each weapons bay is fitted with two hardpoints for carrying a range of bombs and missiles.
Weapons to be cleared for internal carriage include: JDAM (joint direct attack munition), CBU-105 WCMD (wind-corrected munitions dispenser) for the sensor-fused weapon, JSOW (joint stand-off weapon), Paveway IV guided bombs, small diameter bomb (SDB), AIM-120C AMRAAM air-to-air missile and Brimstone anti-armour missile; for external carriage: JASSM (joint air-to-surface stand-off missile), AIM-9X Sidewinder, AIM-132 ASRAAM and Storm Shadow cruise missile.
In September 2002, General Dynamics Armament and Technical Products was selected as the gun system integrator. General Dynamics was awarded a contract for the internally mounted 25mm GAU-22/A gun system for the air force CTOL variant in November 2008. General Dynamics is developing an external gun system for the carrier and marine variants.
Fire control and targeting technology
Lockheed Martin Missile & Fire Control and Northrop Grumman Electronic Sensors and Systems are jointly responsible for the JSF electro-optical system. A Lockheed Martin electro-optical targeting system (EOTS) provides long-range detection and precision targeting, along with the Northrop Grumman DAS (distributed aperture system) thermal imaging system.
EOTS is based on the Sniper XL pod developed for the F-16, which incorporates a mid-wave third-generation FLIR, dual mode laser, CCD TV, laser tracker and laser marker. BAE Systems Avionics in Edinburgh, Scotland provides the laser systems.
DAS consists of multiple infrared cameras (supplied by Indigo Systems of Goleta, California) providing 360° coverage using advanced signal conditioning algorithms. As well as situational awareness, DAS provides navigation, missile warning and infrared search and track (IRST). EOTS is embedded under the aircraft’s nose, and DAS sensors are fitted at multiple locations on the aircraft.
AESA radar and integrated electronic warfare suite
Northrop Grumman Electronic Systems developed the advanced electronically scanned array (AESA) AN/APG-81 multi-function radar. The AN/APG-81AESA combines an integrated radio frequency subsystem with a multifunction array.
The radar system also incorporates the agile beam steering capabilities developed for the APG-77. Northrop Grumman delivered the first radar to Lockheed Martin in March 2005 for flight testing. The 500th AN/APG-81 fire control radar was delivered in November 2019.
BAE Systems information & electronic warfare systems (IEWS) is responsible for the JSF integrated electronic warfare suite, which is installed internally and have some subsystems from Northrop Grumman.
Contractors involved
Systems and suppliers were provided by Honeywell, Goodrich and Paker Aerospace. Collins Aerospace and Elbit Systems formed a joint venture to advanced helmet-mounted display systems for the F-35 programme.
In March 2020, Lynx Software Technologies and Core Avionics & Industrial were selected for supporting the development of the panoramic cockpit display electronic unit (PCD-EU).
Pratt & Whitney won a contract to undertake an F135 upgrade study and operational assessment by the F-35 Joint Program Office to identify propulsion system growth needs for Block 4.2 F-35 aircraft and above in October 2020.
The aircraft development included other suppliers such as ATK Composites, Vought Aircraft Industries, Smiths Aerospace, Honeywell, Parker Aerospace, Moog, EDO Corporation, Goodrich and Stork Aerospace.
Propulsion of the Joint Strike Fighter variation aircraft
All three variants are powered by the Pratt and Whitney low-bypass augmented turbofan F-135 engine, a derivative of the F119 fitted on the F-22.
Each engine is fitted with two BAE Systems full authority digital electronic control (FADEC) systems. Hamilton Sundstrand is providing the gearbox.
On the F-35B, the engine is coupled with a shaft-driven lift fan system for STOVL propulsion. The counter-rotating lift fan, developed by Rolls-Royce Defence, can generate more than 20,000lb of thrust. Doors installed above and below the vertical fan open as the fin spins up to provide vertical lift.
The main engine has a three-bearing swivelling exhaust nozzle. The nozzle, which is supplemented by two roll control ducts on the inboard section of the wing, together with the vertical lift fan provide the required STOVL capability.
