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The Lockheed Martin F-35 Lightning II is a fifth-generation, single-seat, single-engine stealth multirole fighter, that can perform close air support, tactical bombing, and air defense missions. The F-35 has three different models; one is the conventional takeoff and landing variant, the second is short takeoff and vertical-landing variant, and the third is a carrier-based variant.
The F-35 is descended from the X-35, the product of the Joint Strike Fighter (JSF) program. Its development is being principally funded by the United States and the United Kingdom, with other partner governments providing additional funding. It is being designed and built by an aerospace industry team led by Lockheed Martin with Northrop Grumman and BAE Systems as major partners. Demonstrator aircraft flew in 2000, with the first flight on 15 December 2006.
The F-35B STOVL variant was in danger of missing performance requirements in 2004 because it weighed too much – reportedly, by 2,200 pounds (1,000 kg) or 8 percent. In response, Lockheed Martin added engine thrust and shed more than a ton by thinning the aircraft's skin; shrinking the weapons bay and vertical stabilizers; rerouting some thrust from the roll-post outlets to the main nozzle; and redesigning the wing-mate joint, portions of the electrical system, and the portion of the aircraft immediately behind the cockpit.
On 7 July 2006, the US Air Force officially announced the name of the F-35: Lightning II, in honor of Lockheed's World War II-era twin-prop P-38 Lightning and the Cold War-era jet, the English Electric Lightning. English Electric Company's aircraft division was a predecessor of F-35 partner BAE Systems. Lightning II was also an early company name for the aircraft that became the F-22 Raptor.
On 19 December 2008, Lockheed Martin rolled out the first weight-optimized F-35A (designated AF-1). It is the first F-35 to be produced at a full-rate production speed – the assembly line moves at 50 inches (127 centimeters) per hour – and is structurally identical to final production F-35As that will be delivered starting in 2010.
As of 5 January 2009, six F-35s are complete, including AF-1 and AG-1, and 17 are in production. "Thirteen of the 17 in production are pre-production test aircraft, and all of those will be finished in 2009," said John R. Kent, acting manager of F-35 Lightning II Communications at Lockheed Martin Aeronautics Company. "The other four are the first production-model planes, and the first of those will be delivered in 2010 to the U.S. Air Force, and will go to Eglin."
On 6 April 2009, US Secretary of Defense Robert Gates proposed speeding up production for the US to buy 2,443 F-35s.
On 21 April 2009 media reports, citing Pentagon sources, said that during 2007 and 2008, computer spies managed to copy and siphon off several terabytes of data related to F-35's design and the electronics systems, potentially enabling the development of defense systems against the aircraft. However, Lockheed Martin has rejected suggestions that the project has been compromised, saying that it "does not believe any classified information had been stolen".
On 9 November 2009, Ashton Carter, undersecretary of defense for acquisition, technology and logistics, acknowledged that the Pentagon "joint estimate team" (JET) had found possible future cost and schedule overruns in the project and that he would be holding meetings to attempt to avoid these.
The F-35 appears to be a smaller, slightly more conventional, single-engine sibling of the sleeker, twin-engine F-22 Raptor, and indeed drew elements from it. The exhaust duct design was inspired by the General Dynamics Model 200 design, which was proposed for a 1972 supersonic VTOL fighter requirement for the Sea Control Ship.[23] For specialized development of the F-35B STOVL variant, Lockheed consulted with the Yakovlev Design Bureau, purchasing design data from their development of the Yakovlev Yak-141 "Freestyle".[24][25] Although several experimental designs have been built and tested since the 1960s including the Navy's unsuccessful Rockwell XFV-12, the F-35B is to be the first operational supersonic STOVL fighter.
The F-35 is designed to be America's "premier surface-to-air missile killer and is uniquely equipped for this mission with cutting edge processing power, synthetic aperture radar integration techniques, and advanced target recognition."[26]
Some 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 target identification and weapon delivery, and to relay information quickly to other command and control (C2) nodes;
- High speed data networking including IEEE 1394b and Fibre Channel.
- The Autonomic Logistics Global Sustainment (ALGS), Autonomic Logistics Information System (ALIS) and Computerized Maintenance Management System (CMMS) help ensure aircraft uptime with minimal maintenance manpower.
The Teen Series of fighters (F-15, F-16, F/A-18) were notable for always carrying large external fuel tanks, but as a stealth aircraft the F-35 must fly most missions on internal fuel. Unlike the F-16 and F/A-18, the F-35 lacks leading edge extensions (LEX) and instead uses stealth-friendly chines for vortex lift in the same fashion as the SR-71 Blackbird.[30] The small bumps just forward of the engine air intakes form part of the diverterless supersonic inlet (DSI) which is a simpler, lighter and stealthier means to ensure high-quality airflow to the engine over a wide range of conditions.[31]
In spite of being smaller than the F-22, the F-35 has a larger radar cross section. It is said to be roughly equal to a metal golf ball rather than the F-22's metal marble.[32]
The F-35 features a full-panel-width "panoramic cockpit display" (PCD) glass cockpit, with dimensions of 20 by 8 inches (50 by 20 centimeters).[33] A cockpit speech-recognition system (Direct Voice Input) is planned to improve the pilot's ability to operate the aircraft over the current-generation interface. The F-35 will be the first US operational fixed-wing aircraft to use this system, although similar systems have been used in AV-8B and trialled in previous US jets, particularly the F-16 VISTA.[34] In development the system has been integrated by Adacel Systems Inc with the speech recognition module supplied by SRI International.[35] The pilot flies the aircraft by means of a right-hand side stick and left-hand throttle.
A helmet-mounted display system (HMDS) will be fitted to all models of the F-35. A helmet-mounted cueing system is already in service with the F-15s, F-16s and F/A-18s.[36] While some fighters have offered HMDS along with a head up display (HUD), this will be the first time in several decades that a front-line tactical jet fighter has been designed to not carry a HUD.[37]
The Martin-Baker US16E ejection seat is used in all F-35 variants.[38] The US16E seat design balances major performance requirements, including safe-terrain-clearance limits, pilot-load limits, and pilot size. It uses a twin-catapult system that is housed in side rails.[39]
The F-35 includes an advanced, powerful sensor suite.[40] The main sensor on board the F-35 is its AN/APG-81 AESA-radar, designed by Northrop Grumman Electronic Systems.[41] It is augmented by the Electro-Optical Targeting System (EOTS) mounted under the nose of the aircraft, designed by Lockheed Martin.[42] This gives the same capabilities as the Lockheed Martin Sniper XR without compromising the aircraft's stealth.[43][44] A version of the EOTS will also be used by the General Atomics Avenger.
Six additional passive infrared sensors are distributed over the aircraft as part of Northrop Grumman's AN/AAQ-37 distributed aperture system (DAS),[45] which acts as a missile warning system, reports missile launch locations, detects and tracks approaching aircraft spherically around the F-35, and replaces traditional night vision goggles for night operations and navigation. All DAS functions are performed simultaneously, in every direction, at all times. The F-35's AN/ASQ-239 (Barracuda) Electronic Warfare systems are designed by BAE and include Northrop Grumman components.[46] The communications, navigation and identification (CNI) suite is designed by Northrop Grumman and includes the Multifunction Advanced Data Link (MADL). The F-35 will be the first jet fighter that has sensor fusion that combines both radio frequency and IR tracking for continuous target detection and identification in all directions which is shared via MADL to other platforms without compromising their low observability.[47]
Unlike older generations of aircraft, such as the F-22, all software for the F-35 is written in C++ for faster code development. The Integrity DO-178B real-time operating system (RTOS) from Green Hills Software runs on COTS Freescale PowerPC processors.[48]
The F-35's main engine is the Pratt & Whitney F135. The General Electric/Rolls-Royce F136 is being developed as an alternate engine.[49] The STOVL versions of both powerplants use the Rolls-Royce LiftSystem, patented by Lockheed Martin and built by Rolls-Royce. This system is more like the Russian Yak-141 and German VJ 101D/E[50] than the preceding generation of STOVL designs, such as the Harrier Jump Jet in which all of the lifting air went through the main fan of the Rolls-Royce Pegasus engine.
The LiftSystem is composed of a lift fan, drive shaft, two roll posts and a "Three Bearing Swivel Module" (3BSM).[51] The 3BSM is a thrust vectoring nozzle which allows the main engine exhaust to be deflected downward at the tail of the aircraft. The lift fan near the front of the aircraft provides a counter-balancing thrust. Somewhat like a vertically mounted turboprop within the forward fuselage, the lift fan is powered by the engine's low-pressure (LP) turbine via a drive shaft and gearbox. Roll control during slow flight is achieved by diverting pressurized air from the LP turbine through wing mounted thrust nozzles called Roll Posts.[52]
The F-35B lift fan achieves the same 'flow multiplier' effect as the Harrier's huge, but supersonically impractical, main fan. Like lift engines, this added machinery is just deadweight during horizontal flight but provides a net increase in payload capacity during vertical flight. The cool exhaust of the fan also reduces the amount of hot, high-velocity air that is projected downward during vertical takeoff (which can damage runways and aircraft carrier decks). Though complicated and risky, the lift system has been made to work to the satisfaction of DOD officials.
To date, F-136 funding has come at the expense of other parts of the program, reducing the number of aircraft built and increasing their costs.[53] However, the F-136 team has claimed that their engine has a greater temperature margin which may prove critical for VTOL operations in hot, high altitude conditions.[54]
The F135/F136 engines are not designed to supercruise[55] in the F-35.
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