The Lockheed Martin F-35 Lightning II is a family of single-seat, single-engine, all-weather stealth multirole fighters undergoing final development and testing by the United States. The fifth generation combat aircraft is designed to perform ground attack, aerial reconnaissance, and air defense missions. The F-35 has three main models: the F-35A conventional takeoff and landing (CTOL) variant, the F-35B short take-off and vertical-landing (STOVL) variant, and the F-35C carrier-based Catapult Assisted Take-Off But Arrested Recovery (CATOBAR) variant.
The Lockheed Martin F-35 Lightning II,is being developed by Lockheed Martin Aeronautics Company for the US Air Force, Navy and Marine Corps and the UK Royal Navy.
The F-35 is descended from the X-35, which was the winning design of the Joint Strike Fighter (JSF) program. It is being designed and built by an aerospace industry team led by Lockheed Martin. Other major F-35 industry partners include Northrop Grumman, Pratt & Whitney and BAE Systems.
The Lockheed Martin F-35 Lightning II is being designed to be the world's premier strike aircraft through 2040. It is intended that its close and long-range air-to-air capability will be second only to that of the F-22 Raptor. Specifically the F-35’s requirements are that it be: four times more effective than legacy fighters in air-to-air combat, eight times more effective in air-to-ground battle combat, and three times more effective in reconnaissance and suppression of air defenses. These capabilities are to be achieved while still having significantly better range and require less logistics support than legacy aircraft.
The requirement is for: USAF F-35A air-to-ground strike aircraft, replacing F-16 and A-10, complementing F-22 (1763); USMC F-35B – STOVL strike fighter to replace F/A-18B/C and AV-8B (480); UK RN F-35C – STOVL strike fighter to replace Sea Harriers (60); US Navy F-35C – first-day-of-war strike fighter to replace F/A-18B/C and A-6, complementing the F/A-18E/F (480 aircraft).
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 on 30 October 2009. It is being 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. It will be delivered to the UK Ministry of Defence by 2012. The variant is being developed as part of the low-rate initial production (LRIP) 3 and is expected to produce 138 F-35Bs for the UK.
Design
Overview
The F-35 resembles a smaller, single-engine sibling of the twin-engine Lockheed Martin F-22 Raptor and drew elements from it. The exhaust duct design was inspired by the General Dynamics Model 200 design, proposed for a 1972 supersonic VTOL fighter requirement for the Sea Control Ship.Although several experimental designs have been developed since the 1960s, such as the unsuccessful Rockwell XFV-12, the F-35B is to be the first operational supersonic, STOVL stealth fighter.
Acquisition deputy to the assistant secretary of the Air Force, Lt. Gen. Mark D. "Shack" Shackelford has said that 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." Lockheed Martin states the F-35 is intended to have close- and long-range air-to-air capability second only to that of the F-22 Raptor.Lockheed Martin has said that the F-35 has the advantage over the F-22 in basing flexibility and "advanced sensors and information fusion".Lockheed Martin has suggested that the F-35 could replace the USAF's F-15C/D fighters in the air superiority role and the F-15E Strike Eagle in the ground attack role.
Structural composites in the F-35 are 35% of the airframe weight (up from 25% in the F-22).The majority of these are bismaleimide (BMI) and composite epoxy material.The F-35 will be the first mass produced aircraft to include structural nanocomposites, namely carbon nanotube reinforced epoxy.Experience of the F-22's problems with corrosion led to the F-35 using a gap filler that causes less galvanic corrosion to the airframe's skin, designed with fewer gaps requiring filler and implementing better drainage.The relatively short 35-foot wingspan of the A and B variants is set by the F-35B's requirement to fit inside the Navy's current amphibious assault ship parking area and elevators; the F-35C's longer wing is considered to be more fuel efficient.
A United States Navy study found that the F-35 will cost 30 to 40 percent more to maintain than current jet fighters; not accounting for inflation over the F-35's operational lifetime. A Pentagon study concluded a $1 trillion maintenance cost for the entire fleet over its lifespan, not accounting for inflation.The F-35 program office found that as of January 2014, costs for the F-35 fleet over a 53-year life cycle was $857 billion. Costs for the fighter have been dropping and accounted for the 22 percent life cycle drop since 2010.Lockheed stated that by 2019, pricing for the fifth-generation aircraft will be less than fourth-generation fighters. An F-35A in 2019 is expected to cost $85 million per unit complete with engines and full mission systems, inflation adjusted from $75 million in December 2013.
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| An F-35A powerplant on display, 2014 |
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| The Pratt & Whitney F135 engine with Rolls-Royce LiftSystem, including roll posts, and rear vectoring nozzle for the F-35B, at the 2007 Paris Air Show |
Two different jet engines are being developed for the F-35; the Pratt & Whitney F135 and the General Electric/Rolls-Royce F136. The STOVL versions of both powerplants use the innovative 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 than the preceding generation of STOVL designs, such as the Harrier Jump Jet.
The F135 and F136 engines are not designed to supercruise.However, the F-35 can briefly fly at Mach 1.2 for 150 miles.The F135 is the second (radar) stealthy afterburning jet engine. Like the Pratt & Whitney F119 from which it was derived, the F135 has suffered afterburner pressure pulsations, or 'screech' at low altitude and high speed.The F-35 has a maximum speed of over Mach 1.6. With a maximum takeoff weight of 60,000 lb (27,000 kg), the Lightning II is considerably heavier than the lightweight fighters it replaces.
The LiftSystem is composed of a lift fan, driveshaft, clutch, 2 roll posts and a "3 Bearing Swivel Module" (3BSM). 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 driveshaft 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.
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 potentially risky, the lift system has been made to work to the satisfaction of DOD officials.
Armament
The F-35A is armed with a GAU-22/A, a four-barrel version of the 25 mm GAU-12 Equalizer cannon.The cannon is mounted internally with 182 rounds for the F-35A or in an external pod with 220 rounds for the F-35B and F-35C; the gun pod has stealth features.The F-35 has two internal weapons bays, and external hardpoints for mounting up to four underwing pylons and two near wingtip pylons. The two outer hardpoints can carry pylons for the AIM-9X Sidewinder and AIM-132 ASRAAM short-range air-to-air missiles (AAM) only.The other pylons can carry the AIM-120 AMRAAM BVR AAM, , AGM-158 Joint Air to Surface Stand-off Missile (JASSM) cruise missile, and guided bombs. The external pylons can carry missiles, bombs, and external fuel tanks at the expense of increased radar cross-section, and thus reduced stealth.
There are a total of four weapons stations between the two internal bays. Two of these can carry air-to-surface missiles up to 2,000 lb (910 kg) in A and C models, or two bombs up to 1,000 lb (450 kg) in the B model; the other two stations are for smaller weapons such as air-to-air missiles.The weapon bays can carry AIM-120 AMRAAM, AIM-132 ASRAAM, the Joint Direct Attack Munition (JDAM), Paveway series of bombs, the Joint Standoff Weapon (JSOW), Brimstone anti-tank missiles, and cluster munitions (Wind Corrected Munitions Dispenser).An air-to-air missile load of eight AIM-120s and two AIM-9s is possible using internal and external weapons stations; a configuration of six 2,000 lb (910 kg) bombs, two AIM-120s and two AIM-9s can also be arranged.The Terma A/S multi-mission pod (MMP) could be used for different equipment and purposes, such as electronic warfare, aerial reconnaissance, or rear-facing tactical radar.
Lockheed Martin states that the weapons load can be configured as all-air-to-ground or all-air-to-air, and has suggested that a Block 5 version will carry three weapons per bay instead of two, replacing the heavy bomb with two smaller weapons such as AIM-120 AMRAAM air-to-air missiles.Upgrades are to allow each weapons bay to carry four GBU-39 Small Diameter Bombs (SDB) for A and C models, or three in F-35B.Another option is four GBU-53/B Small Diameter Bomb IIs in each bay on all F-35 variants.The F-35A has been outfitted with four SDB II bombs and an AMRAAM missile to test adequate bay door clearance,as well as the C-model, but the VTOL F-35B will not be able to carry the required load of four SDB IIs in each weapons bay upon reaching IOC due to weight and dimension constraints; F-35B bay changes are to be incorporated to increase SDB II loadout around 2022 in line with the Block 4 weapons suite.The Meteor (missile) air-to-air missile may be adapted for the F-35, a modified Meteor with smaller tailfins for the F-35 was revealed in September 2010; plans call for the carriage of four Meteors internally.The United Kingdom planned to use up to four AIM-132 ASRAAM missiles internally, later plans call for the carriage of two internal and two external ASRAAMs.The external ASRAAMs are planned to be carried on "stealthy" pylons; the missile allows attacks to slightly beyond visual range without employing radar.
Norway and Australia are funding an adaptation of the Naval Strike Missile (NSM) for the F-35. Under the designation Joint Strike Missile (JSM), it is to be the only cruise missile to fit the F-35's internal bays; according to studies two JSMs can be carried internally with an additional four externally.The F-35 is expected to take on the Wild Weasel mission, though there are no planned anti-radiation missiles for internal carriage.The B61 nuclear bomb was initially scheduled for deployment in 2017;as of 2012 it was expected to be in the early 2020s,and in 2014 Congress moved to cut funding for the needed weapons integration work.Norton A. Schwartz agreed with the move and said that "F-35 investment dollars should realign to the long-range strike bomber".NATO partners who are buying the F-35 but cannot afford to make them dual-capable want the USAF to fund the conversions to allow their Lightning IIs to carry thermonuclear weapons. The USAF is trying to convince NATO partners who can afford the conversions to contribute to funding for those that cannot. The F-35 Block 4B will be able to carry two B61 nuclear bombs internally by 2024.
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| AN/APG-81 AESA-radar |
Northrop Grumman Electronic Systems is developing the advanced electronically scanned array (AESA) AN/APG-81 multi-function radar. The AN/APG-81AESA will combine an integrated radio frequency subsystem with a multifunction array.
The radar system will also incorporate 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 F-35's radar-absorbent materials are designed to be more durable and less maintenance-intensive than those of its predecessors. At optimal frequencies, the F-35 compares favorably to the F-22 in stealth, according to General Mike Hostage, Commander of the Air Combat Command.Like other stealth fighters, however, the F-35 is more susceptible to detection by Low-frequency radars due to the Rayleigh scattering resulting from the aircraft's physical size. However, such radars are also conspicuous, susceptible to clutter, and have low precision.Although fighter-sized stealth aircraft could be detected by low-frequency radar, missile lock and targeting sensors primarily operate in the X-band, which F-35 RCS reduction is made for, so they cannot engage unless at close range.Because the aircraft's shape is important to the RCS, special care must be taken to match the "boilerplate" during production.Ground crews require Repair Verification Radar (RVR) test sets to verify the RCS after performing repairs, which is not a concern for non-stealth aircraft.
Acoustic
In 2008, the Air Force revealed that the F-35 would be about twice as loud at takeoff as the McDonnell Douglas F-15 Eagle and up to four times as loud during landing.Residents near Luke Air Force Base, Arizona and Eglin Air Force Base, Florida, possible F-35 bases, requested environmental impact studies be conducted regarding the F-35's noise levels.In 2009, the city of Valparaiso, Florida, adjacent to Eglin AFB, threatened to sue over the impending F-35 arrival; this lawsuit was settled in March 2010.In 2009, testing reportedly revealed the F-35 to be: "only about as noisy as an F-16 fitted with a Pratt & Whitney F100-PW-200 engine...quieter than the Lockheed Martin F-22 Raptor and the Boeing F/A-18E/F Super Hornet."An acoustics study by Lockheed Martin and the Air Force found F-35's noise levels to be comparable to the F-22 and F/A-18E/F.A USAF environmental impact study found that replacing F-16s with F-35s at Tucson International Airport would subject more than 21 times as many residents to extreme noise levels.The USN will need to redesign hearing protection for sailors to protect against the "thundering 152 decibels" of the F-35.The Joint Strike Fighter program office found in October 2014 that the F-35B's take-off noise was only two decibels higher than a Super Hornet, a virtually indistinguishable difference to the human ear, and is even 10 decibels quieter when flying formations or landing.
Cockpit
The F-35 features a full-panel-width "panoramic cockpit display (PCD)", with dimensions of 20 by 8 inches (50 by 20 centimeters). A cockpit speech-recognition system (Direct Voice Input) is planned to improve the pilot's ability to operate the aircraft over the current-generation. The F-35 will be the first U.S. operational fixed-wing aircraft to use this system, although similar systems have been used in AV-8B and trialled in previous U.S. jets, particularly the F-16 VISTA. In development the system has been integrated by Adacel Systems Inc with the speech recognition module supplied by SRI International.
A helmet mounted display system (HMDS) will be fitted to all models of the F-35. While some fourth-generation fighters (such as the Swedish JAS 39 Gripen) 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.
Problems with the Vision Systems International helmet-mounted display led Lockheed Martin-Elbit Systems to issue a draft specification for alternative proposals in early 2011, to be based around the Anvis-9 night vision goggles.BAE Systems was selected to provide the alternative system in late 2011.The BAE Systems alternative helmet was to include all the features of the VSI system.,however, adopting the alternative helmet would have required a cockpit redesign,but in 2013 development on the alternative helmet was halted due to progress on the baseline helmet
The pilot flies the aircraft by means of a right-hand side-stick and left-hand throttle, both of which are supplied by BAE Systems.
The Martin-Baker US16E ejection seat is used in all F-35 variants. 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.
Sensors and avionics
The F-35's sensor and communications suite has situational awareness, command and control and network-centric warfare capabilities.The main sensor on board is the AN/APG-81 Active electronically scanned array-radar, designed by Northrop Grumman Electronic Systems.It is augmented by the nose-mounted Electro-Optical Targeting System (EOTS),it provides the capabilities of an externally mounted Sniper Advanced Targeting Pod pod with a reduced radar cross-section.The AN/ASQ-239 (Barracuda) system is an improved version of the F-22's AN/ALR-94 electronic warfare suite, providing sensor fusion of Radio frequency and Infrared tracking functions, advanced radar warning receiver including geolocation targeting of threats, multispectral image countermeasures for self-defense against missiles, situational awareness and electronic surveillance, employing 10 radio frequency antennae embedded into the edges of the wing and tail.In September 2015, Lockheed unveiled the "Advanced EOTS" that offers short-wave infrared, high-definition television, infrared marker, and superior image detector resolution capabilities. Offered for the Block 4 configuration, it fits into the same area as the baseline EOTS with minimal changes while preserving stealth features.
Six additional passive infrared sensors are distributed over the aircraft as part of Northrop Grumman's electro-optical AN/AAQ-37 Distributed Aperture System (DAS),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 devices. All DAS functions are performed simultaneously, in every direction, at all times. The electronic warfare systems are designed by BAE Systems and include Northrop Grumman components.Functions such as the Electro-Optical Targeting System and the electronic warfare system are not usually integrated on fighters.The F-35's DAS is so sensitive, it reportedly detected the launch of an air-to-air missile in a training exercise from 1,200 mi (1,900 km) away, which in combat would give away the location of an enemy aircraft even if it had a very low radar cross-section.
The electronic warfare and electro-optical systems are intended to detect and scan aircraft, allowing engagement or evasion of a hostile aircraft prior to being detected.The CATbird avionics testbed has proved capable of detecting and jamming radars, including the F-22's AN/APG-77.The F-35 was previously considered a platform for the Next Generation Jammer; attention shifted to using unmanned aircraft in this capacity instead.Several subsystems use Xilinx FPGAs;these COTS components enable supply refreshes from the commercial sector and fleet software upgrades for the software-defined radio systems.
Lockheed Martin's Dave Scott stated that sensor fusion boosts engine thrust and oil efficiency, increasing the aircraft's range.Air Force official Ellen M. Pawlikowski has proposed using the F-35 to control and coordinate multiple unmanned combat aerial vehicles (UCAVs). Using its sensors and communications equipment, a single F-35 could orchestrate an attack made by up to 20 armed UCAVs.
First flights of Lockheed's F-35 variations
The F-35C took off on its first flight in November 2011. The F-35A fighter was delivered to Eglin Air Force Base in October 2011 and is under functional test; the F-35B was inaugurated in October 2011.
The first flight of the F-35 is powered by the GE Rolls-Royce F136 engine. Critical design review was completed in February 2008.
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. Denmark and Italy (requirement 131 F-35A and B) signed in February 2007. In May 2008, Israel requested the sale of 25 F-35A aircraft with 50 options.
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.
In September 2004, Lockheed Martin announced that, following concerns over the weight of the STOVL F-35B, design changes had reduced the aircraft weight by 1,225kg while increasing propulsion efficiency and reducing drag. The weight requirements will also call for a smaller internal weapons bay than on the other variants.
Training centre at Elgin Air Force Base and F-35 operational bases
An integrated training centre for the F-35 fighter programme has been set up at Elgin Air Force Base in the US. The training centre was inaugurated in November 2010 and will be fully operational by 2013.
A total of 11 base locations were unveiled for the F-35 Lightning joint strike fighter. Of the 11, six were selected to carry out operations and five to be training bases.
The six bases implementing F-35 operations are Burlington International Airport Guard Station, Vermont; Hill AFB, Utah; Jacksonville International Airport Air Guard Station, Florida; Mountain Home AFB, Idaho; Shaw AFB, South Carolina; and McEntire Air Guard Base, South Carolina. The five bases for training purposes are Boise Air Terminal Air Guard Station, Idaho; Eglin Air Force Base, Florida; Holloman Air Force Base, New Mexico; Luke AFB, Arizona; and Tucson International Airport Air Guard Station, Arizona.
The selected locations will be finalised after implementing environmental impact analysis.
Accidents
On 23 June 2014, an F-35A preparing to take off on a training flight at Eglin Air Force Base experienced a fire in the engine area. The pilot escaped unharmed. The accident caused all training to be halted on 25 June, and all flights halted on 3 July.During the incident investigation, engine parts from the burned aircraft were discovered on the runway, indicating it was a substantial engine failure.The fleet was returned to flight on 15 July with restrictions in the flight envelope.Preliminary findings suggests that excessive rubbing of the engine fan blades created increased stress and wear and eventually resulted in catastrophic failure of the fan.
In Early June 2015, the USAF Air Education and Training Command (AETC) issued its official report on the incident. It found that the incident was the result of a failure of the third stage rotor of the engine's fan module. The report explained that "pieces of the failed rotor arm cut through the engine's fan case, the engine bay, an internal fuel tank, and hydraulic and fuel lines before exiting through the aircraft's upper fuselage". Pratt and Whitney, the engine manufacturers, developed two remedies to the problem. The first is an extended "rub-in" to increase the gap between the second stator and the third rotor integral arm seal. The second is the redesign to pre-trench the stator. Both should be complete by early 2016. Cost of the problem was estimated at USD 50 million. All aircraft resumed operations within 25 days of the incident.