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Lockheed Martin Lightning II

F-35 Joint Strike Fighter

Selected as the UK's

Joint Combat Aircraft (JCA)



(Above) The winning Lockheed Martin F-35 Lightening II Joint Strike Fighter.



(Above)  Artists impression of a joint proposal by McDonnell Douglas, British Aerospace and Northrop Grumman - an early loser.



(Above) Artists concept of the STOVL variant of the Boeing JAST / JSF proposal.

JSF Concept Demonstrator Aircraft

(Above) 18 September 2000 saw the first flight of the Boeing X-32A (Conventional and Carrier) concept demonstrator ...

 .... and (below) 24 October 2000 the first flight of the Lockheed Martin X-35A (Conventional) demonstrator



(Above) The  Lockheed Martin X-35B (STOVL variant) first flew on 23 June 2001, successfully demonstrating its vertical take off and landing ability.


JSF Preferred Weapon System Concept

(Below) Line diagram's of the Lockheed Martin F-35B STOVL and F-35C CV JSF "Preferred Weapon System Concept" configuration 240-4 (dating to about June 2006), reflecting weight reduction and other design changes made since 2002.

When the the upper F-35B is compared with the (lower) F-35C variant, notice the bulged area aft of the cockpit to house the lift fan and the two sets of inlet doors, the forward doors cover the main inlet for the lift fan, while the aft set covers the auxiliary intake for the engine.  Also note the reduced glazed canopy area, much smaller main wing and tailplane, and shorter engine nozzle.




(Above) An image from late 2004 of the weight reduced F35B.


(Above) Although the UK has officially selected the STOVL F-35B variant, it remains very interested in the US Navy's conventional F-35C variant - increasingly as land based replacement for the Tornado GR4 rather than for carrier based operations.


(Above) The latest (2006) artists impressions of the F-35C, reflecting recent design changes including a new larger wing.


(Above) First flight of the first F-35A prototype on 15 December 2006.


(Below) A now dated (2003 JSF data?) but still interesting comparison.



(Above) F-35B cutaway graphic by John Batchelor




Paris Air Show -  Le Bourget 2005

Joint Strike Fighter

This model of a UK F-35B is shown carrying a pair of Storm Shadow air-to-surface missiles, a pair of Meteor air-to-air missiles underwing, and an ASRAAM in the open weapons bay.  In practice the intregration of Meteor is unfunded, integration of Storm Shadow is being delayed, and ASRAAM will not be cleared for external carriage.



Relatively little data has yet been published regarding the specification of the Lockheed Martin JSF F-35 "Preferred Weapon System Concept" and the following is derived from a variety of sources:

Characteristic UK STOVL variant

Single Pratt and Whitney F135 (F119-PW-100 derivative with scaled-up fan and additional low-pressure turbine stage) reheated turbofan of up to 40,000lbs (179 kN ) in reheat.  Fitted with Rolls Royce designed rotating nozzle for STOVL operations.  39,000 lbs in vertical lift mode for STOVL version.  In 2006 the DoD cancelled that it wanted to plans to develop the General Electric/Rolls Royce  F136 engine as an alternative option.

The lift fan, developed by Rolls-Royce, will have 18500 lbs (82 kN) of thrust.

Empty 30,697 lb; internal fuel 13,400 lb; max external fuel 10,000 lb; max external payload 15,000 lb; max TOW over 50,000 lbs; bring-back load for vertical landing: about 5,000 lb payload plus fuel reserves 
Span:   35ft  
Length:   50.5ft
Height:   15 ft
Wing Area:   460 square feet
Max Speed:  Mach 1.8 clean
Combat Radius:   929 km (496 nm) unrefueled.
"Buddy" air-to-air refuelling system to be available.
Fly away unit cost  $54-61 million (FY2002)
Armament:   The F-35 (JSF) has two internal weapons bays in the fuselage , each of which can accommodate a single "Joint Direct Attack Munition (JDAM)" GPS-guided bomb and an AIM-120 Advanced Medium-Range Air to Air Missile (AMRAAM) - i.e. an internal load of two AIM-120 AMRAAMs and two bombs or other missiles.  The two bays have two doors each, with the AIM-120 AMRAAM missile fitted on a launch rail on the inner door.   The bomb can be up to  1135 kg, but the weapons bay has been shortened by 14 inches in the F-35B variant which is thus unable to accommodate some weapons such as the the 2000 lbs GBU-31 JDAM bomb which can be carried in the F-35A/C variants.  There are three external hardpoints (2270 kg, 1135 kg, 136 kg going out from the fuselage) under each wing for non-stealthy missions , plus one under the fuselage (450 kg) and missile rails on the wingtips (135 kg) suitable for small AAM's and electronic pods.  The inner pylon on each wing will be "wet" ( i.e. can take fuel drop tanks), while the outer pylon will be rated for up to 1,135 kilograms (2,500 pounds).

UK integrated weapons include a 1000lb laser guided bomb (1 per bay), the ASRAAM missile (2  per bay),  Brimstone anti-armour munitions, and Storm Shadow cruise missiles (1 only, carried externally).  The MBDA Meteor air-to-air missiles may also eventually be carried by UK aircraft, but LM has not been asked by the MOD(UK) to do any detailed engineering studies and the missile probably wont fit in the shortened weapons bay of the F-35B.

A large number of weapons (including the AGM-84D-1 Harpoon and AGM-84H SLAM-ER missiles;  Mk.62 and Mk.63 Quickstrike mines; and UK Paveway II and III bombs) and pods that were originally planned for integration with the JSF have now been dropped or deferred.  Several more (including the AGM-65 Maverick and HARM missiles) may also be dropped or deferred.

The STOVL F-35B will not have a built-in gun, but it will be able to take a 25mm gun pod.

The F-35 Block 3 will reach Initial Operating Capability about 2015.  Various sources list the following weapons for internal carriage. 

* 25 mm GAU-12U cannon (F-35A only)
* AGM-154A JSOW (glide bomb, 450 kg) (F-35A/C only)
* BSU-33
* CBU-103/104/105 (WCDM)
* CBU-87/89 Cluster Munition
* GBU-12 Paveway II (500lb) LGB
* GBU-31 JDAM (2000lb) and GBU-31 JDAM PIP (F-35A/C only)
* GBU-32 JDAM (1000lb) and GBU-32 JDAM PIP
* GBU-38 JDAM (500lb) and GBU-38 JDAM PIP
* GBU-39 Small Diameter Bomb
* UK 1000 lbs LDGB
* UK AIM-132 ASRAAM (deferred to 2030)
* UK Brimstone (deferred to 2030)
On the external stations, the following missiles, bombs and tanks can be carried:
* 25 mm GAU-12 belly gun pod (F-35B/C only)
* 1815 litre-tank, 2270 litre-tank
* AGM-65 Maverick
* AIM-9X Sidewinder
* BDU-57/58/60 laser-guided training round
* CBU-99/100 Rockeye II Cluster Munition
* GBU-12 Paveway II (500lb) LGB
* GBU-10 Paveway II (2000lb) LGB
* GBU-16 Paveway II (1000lb) LGB
* GBU-24 Paveway III (2000lb) LGB
* GBU-31 JDAM (2000lb) and GBU-31 JDAM PIP
* Mk.82 BLU-111 (500lb) LDGB
* Mk.82 BLU-111 Ballute (500lb) HDGP
* Mk.83 BLU-110 (1000lb) LDGB
* Mk.83 BSU-85 LDGB
* Mk.84 BSU-84 (2000lb) LD/HDGP
* MXU-648 Cargo Pod
* UK Storm Shadow
* SUU-20/SUU-5003 practice bomb and rocket dispenser
* UK Paveway IV

The UK weapons were originally threshold weapons for JSF, e.g.  ASRAAM was in Block 3 (SDD), while Brimstone and Storm Shadow were in Block 4 and expected to enter service by 2022.  However it  was revealed in late 2005 that the MOD had cancelled or deferred the integration of UK weapons as a cost saving measure, and they now won't enter service until 2025.  There is also no requirement for the Meteor air-to-air missile to be fitted to UK JSF's, despite the lobbying of industry.

Crew:  Single-seat version only.
Recognition:   Similar appearance to the F-22 Raptor also designed by Lockheed Martin.  Slim profile with large forward-angled intakes mounted on fuselage. Large vertical and horizontal rear surfaces extending aft of single jetpipe.
Spares:  Highly common multi-service aircraft.  The original objective was 90 percent commonality for all service variants, which will significantly reduces manufacturing, support and training costs.  This has been subsequently revised to 70-90% parts commonality by cost, less by number.

Layout of weapons bays and hard points:

Internal weapons:


External weapons:




The Lockheed Martin F-35 Lightning II is the result of the USA's Defense Department's Joint Strike Fighter (JSF) program, which sought to build a multi-role fighter optimized for the air-to-ground role, designed to affordably meet the needs of the American and British armed services, with improved survivability, precision engagement capability, the mobility necessary for future joint operations, and reduced life cycle costs.  By using many of the same technologies developed for the F-22 Raptor, its hoped that the F-35 will be able to capitalize on commonality and modularity to maximize affordability.

Lockheed Martin is developing three major versions of the Joint Strike Fighter for the United States Navy, US Air Force and finally for the US Marine Corps.  The Royal Air Force and Royal Navy are currently expected the USMC variant, with minimum UK-only national modifications.  All versions have the same fuselage and internal weapons bay.  The F-35 has common outer mould lines with similar structural geometries, identical wing sweeps, and comparable tail shapes. The weapons are stored in in two parallel bays located aft or rear of the main landing gear. The canopy, radar, ejection system, subsystems, and avionics are all common among the different versions. The same core engine(s) can power the different versions of the F-35.

Other key systems on the F-35 include:

  1. Northrop Grumman advanced electronically scanned array (AESA) multi-function radar
  2. Snader/Litton Amecon electronic countermeasures equipment
  3. Lockheed Martin electro-optical targeting system
  4. Northrup Grumman distributed aperture infrared sensor (DAIRS) thermal imaging system
  5. Vision Systems International advanced helmet-mounted display


JSF Programme History

What is known today as the F-35 Joint Strike Fighter Program was originally known as the Joint Advanced Strike Technology (JAST) Program. The goal of the JAST program was not to have developed a new aircraft, but instead it was to mature the technologies that a new series of tactical aircraft could use.

JAST was chartered to mature technologies, develop requirements, and demonstrate concepts for affordable next-generation joint strike warfare.  As JAST plans took shape, it became apparent that JAST would be funding one or more concept demonstrator aircraft starting in 1996–about the time the Anglo-American ASTOVL program planned to enter its Phase III (full-scale flight demonstrators).  The ASTOVL project, as an advanced technology concept for a future joint-service strike/fighter, appeared consistent with the JAST charter.  It was therefore agreed by the management of both programs, that JAST would become the U.S. service “sponsor” for the flight demonstration phase of ASTOVL, if Phase II were successful and if the concept appeared to be able to satisfy the requirements of at least two of the three U.S. services participating in JAST. However, FY95 budget legislation passed in October 1994 by the U.S. Congress directed that ASTOVL be merged into JAST immediately and this occurred in in November 1994; the programme being renamed Joint Strike Fighter (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, the UK having agreed to fund 35% of the ASTOVL portion of JSF on 28 October 1994. 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 to participate in event of securing contract. Boeing also 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). Both variants to be built on common assembly line, with production for US and UK military expected to total around 3,000, including just over 750 ASTOVL-configured aircraft.

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. X-32 and X-35 designations allocated to demonstration phase which was planned to conclude in February 2001, although it now appears likely to continue until mid-year; successful teams will each build two aircraft, with CTOL version to fly first. STOVL versions to fly second and participate in assessment and demonstration of hover and transition qualities.

Three candidates were in contention for WSCD, originating from Boeing, Lockheed Martin and McDonnell Douglas/British Aerospace/Northrop Grumman.

All three contenders chose Pratt & Whitney's F119 engine for their WSCD 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 YF120-FX version over four year period; this likely to result in follow-on development programme starting in 2001, culminating in full-scale SDD from 2004. If necessary, it is planned that the F120 engine will be available from the 72nd production aircraft onwards.

On 16 November 1996, US Secretary of Defense, William J Perry announced that Boeing and Lockheed Martin had been chosen to participate in forthcoming WSCD and that the team headed by McDonnell Douglas had been eliminated. Simultaneously, Boeing was awarded a US$661.8 million contract for the next phase of the JSF programme, while Lockheed Martin received US$718.8 million; 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.

The  Concept Demonstration Phase (CDP) of the JSF programme began in November 1996 and completed in October 2001.   The UK was a full collaborative partner in the CDP and contributed $200 million to the approximately $2 billion costs.  UK staff were fully integrated into the activities of the JSF Program Office. A number of other countries also participated in this phase, though not as full partners.

Boeing and Lockheed Martin each received CDP contracts from the US DoD, each worth some $700 million.  British Aerospace (now BAE Systems) was a partner in the failed McDonnell Douglas (now part of Boeing) JSF bid.  BAE Systems and also Northrop Grumman later teamed with the Lockheed Martin programme to help build their two concept demonstration X-35 Joint Strike Fighter aircraft.   BAE is provided expertise in the areas of short takeoff and vertical landing technologies, systems integration, and low-cost design and manufacturing

The Concept Demonstration Phase was intended to accomplish the following key objectives:

  • develop fully validated and affordable operational requirements;

  • demonstrate key technologies (including Concept Demonstration Aircraft) to reduce life cycle cost of the weapon system;

  • develop mature weapon system concept designs and proposals for Engineering and Manufacturing Development (EMD - equivalent to UK Full Development), later renamed System Development and Demonstration (SDD).

Boeing's X-32 design incorporated a direct-lift concept using a two-dimensional thrust vectoring propulsion nozzle and swiveling retractable lift nozzles for the X-32B STOVL version; the X-32A CTOL derivative lacks STOVL features. Trials with a 94 per cent scale YF119-powered model of the STOVL configuration began at Tulalip, near Seattle, during 1995, as part of more than 5,300 hours of JAST/JSF-related testing which was completed in second quarter of 1996.

Lockheed Martin's X-35 design has a trapezoidal wing planform which initially featured foreplanes, although these since deleted; STOVL version embodies a lift fan, shaft-driven by a modified F119 with a vectoring lift/cruise nozzle developed by Rolls-Royce; lift fan replaced by extra fuel in the CTOL version. Lockheed Martin also turned to Russia for technical expertise, purchasing design data from Yakovlev; and used an 86 per cent subscale model (originally developed for the CALF project and fitted with a Pratt & Whitney F100-PW-220 engine plus an Allison shaft-driven lift fan) for testing. This was initially hover tested on an outdoor stand at NASA's Ames Research Center during July and August 1995, before being installed in the 24 × 36 m wind tunnel at Mountain View, California, in September for aerodynamic hover and transition trials which began in December. Wind-tunnel testing concluded on 5 March 1996, marking end of three-year effort to design, build and test large-scale powered model of VTOL version of JSF; this included 196 hours of propulsion system testing in 1995-96, representative of about 2,400 vertical take-offs and landings.

Further international interest resulted in three European nations joining JSF programme as limited collaborative partners at cost of US$10 million each, spread over five year period; Netherlands and Norway signed MoU committing them to participate in WSCD programme on 16 April 1997, with Denmark following suit later in year. In each case, JSF viewed as potential replacement for F-16 Fighting Falcon; Italy became `informed partner' in April 1998 and announced intention in January 1999 of deeper involvement; Turkish partnership agreement signed 16 June 1999 as Foreign Military Sales customer (fourth-level participation). Other nations known to have expressed interest include Australia, Canada, France, Germany, Greece, Israel, Singapore, Spain and Sweden, which have all been briefed on JSF programme. For engineering and manufacturing development phase, four partnership options available.  Most costly is Level 1, which entails responsibility for 10 per cent of cost; UK is only partner at this level. Italy, Netherlands and Turkey are Level 2 partners, each contributing 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 Canada meets the cost alone.  Finally, Foreign Military Sales Level involves minimum contribution of US$75 million, but no subscribers by mid-2000.

1997-2000 saw the successful completion of initial and final design reviews. Lockheed Martin passed initial design review milestone in mid-June 1997, with Boeing following suit at beginning of September 1997, allowing both companies to begin the fabrication and assembly process.  Final design review hurdle passed by Lockheed Martin in third quarter of 1998, with Boeing candidate completing this in fourth quarter; by then, both manufacturers reporting good progress with assembly of prototypes and Lockheed Martin had produced a full-size mock-up.

Notable power plant-related events and developments during same period include critical design review (CDR) of Pratt & Whitney F119 derivatives (SE611 for X-35; SE614 for X-32). CDR began in August 1997 and was completed successfully in third quarter of year, allowing work to start on assembly of both basic types of engine in October; ground testing of all four engine variants began during 1998, with SE611C for X-35A, SE611S for X-35B, SE614C for X-32A and SE614S for X-32B.

Multifunction integrated RF system/multifunction nose array (MIRFS/MFA) avionics package also specified for JSF during latter half of 1997; Northrop Grumman Electronic Systems and Sensors Division in competition with Raytheon Systems Company, with selection of winning equipment expected in 2001. Earlier, on 4 June 1997, Raytheon chosen to provide integrated core processor for Lockheed Martin X-35.

On armament front, consideration was given to development of advanced 25 mm calibre gun at cost of about US$60 million. This idea subsequently abandoned and Boeing/Mauser proposal for 27 mm gun adopted by both JSF teams in May 1999; integral carriage a possibility and has been endorsed by USAF, although US Navy has no requirement for a gun and is concerned about potential penalties associated with provision of integral armament; USMC known to prefer pod-mounted weapon and Royal Navy likely to follow suit.

Plans also revealed for various test projects allied to JSF programme. First announcement, in October 1997, concerned use of UK Defence Evaluation and Research Agency (DERA) vectored-thrust aircraft advanced control (VAAC) first-generation Harrier two-seater in testing flight control systems, which duly took place in 1998. Lockheed Martin revealed plans, in November 1997, to employ AFTI/F-16 for integrated subsystem technology demonstration of electrically operated flight control actuator system and modular 270 V DC electrical power system. Installation completed in 1998, with aircraft used for six month test and evaluation programme at Edwards AFB, California, during 1999.

JSF acquisition planning little affected by Quadrennial Defense Review of May 1997 and production run of successful design for US and UK still expected to number at least 3,000, following RAF revelation in May 1997 that it was considering CTOL version as replacement for Harrier GR. Mk 7. Subsequently, in June, USAF launched year-long study of plans to include some STOVL-configured aircraft in overall purchase as replacement for A-10 Thunderbolt II in CAS/BAI role; further announcement on 23 September 1997 revealed that USAF considering buying sufficient STOVL JSFs to equip two Fighter Wings (approximately 200 aircraft in total, including allowance for pilot training and maintenance requirements).

First flights of both companies conventional demonstrators occurred in Autumn 2000, although first flights of the STOVL demonstrators were badly delayed and not occur until March (Boeing X-32B and June (Lockheed Martin X-35B). This is of course affected the progress of the source selection process for the Prime Contractor which began in early February 2001 when Boeing and Lockheed Martin submitted their engineering and manufacturing proposals, and was completed on 15 August when final proposals, including the data from the STOVL flight test programmes, were submitted.  

Inevitably this delayed completion of the current Concept Demonstration Phase which did not complete until 26 October 2001, when it was announced that Lockheed Martin had had been selected as prime contractor for the next SDD Phase.  Entry into this occurred in November 2001.  During the SDD phase the winning bidder will produce the service standard or preferred weapon systems concept JSF.

Lockheed Martin had hoped to fly its demonstrators in first half of 2000, but it was not until 24 October 2000 that the X-32A first flew.  By this time Lockheed Martin had modified its original plan; its initial aircraft was still used to test CTOL as the X-35A, before then being reconfigured as the X-35B for the STOVL demonstration. On completion of its flight testing the X-32A was returned to the factory and its first flight as a X-32B occurred on 23 in June 2001.  The second aircraft, which was originally to be used as STOVL demonstrator, instead emerged as a X-35C with carrier-compatible attributes of US Navy version and first flew on 16 December 2000. 

Boeing formally unveiled its X-32A and X-32B variants at Palmdale on 14 December 1999; X-32A CTOL version was then expected to make its first flight by April 2000 with the X-32B STOVL derivative following in mid-2000. However, maiden flight of X-32A was delayed until 18 September 2000. This took place from Palmdale, with aircraft landing at Edwards AFB at end of 20-minute sortie; landing gear locked down throughout and not retracted until 10th flight on 10 October.  The X-32A completed flight testing on Feb. 3 after 66 flights and 50.4 flight hours with six different Boeing and government pilots. The X-32A demonstrated conventional takeoff and landing for the U.S. Air Force and carrier-approach flying qualities for the U.S. Navy.  The first flight of the Boeing X-32B finally took place on 29 March 2001. There is no X-32C CV variant as the X-32A also successfully undertook all the carrier approach testing. 

jsf-devsm.gif (10611 bytes)

Top,  JSF Programme Schedule as planned in 2001.

Upper Middle, JSD SDD Schedule as planned in October 2003.

Lower Middle, Proposed revised plan as at June 2004

Bottom, JSD SDD Schedule as planned in September 2005 after slippage.

(click on image for full size chart)

Following assessment of proposals and flight test results, selection of the winning JSF design was originally expected to occur in May-June 2001, at which time the engineering and manufacturing development (EMD) contract was due to be awarded; however the EMD go-ahead slipped as result of both programme delays and the Strategic Defense Review undertaken by the new Bush Administration and was delayed until 26 October 2001.

The Final Joint Operational Requirements Document (JORD) was issued in March 2000, providing a basis for proposals for the EMD phase following the WSCD.  Lockheed Martin was selected on 26 October 2001 as prime contractor for the $18.9 billion System Development and Demonstration (SDD) phase - the renamed EMD phase.  SDD started in November 2001 and will extend to 2008, with the first flight of an SDD-dedicated JSF set for 2005, followed by the start of operational testing in 2008.  Lockheed Martin will produce 14 flying models and seven ground-test vehicles under the initial development contract, with all three planned variants represented.

Delivery of the first operational aircraft is scheduled for early in FY08 and the US production rate is expected to rise to a peak of 122 per year by 2011. Current plans envisage a start to be made on quantity production of the successful design in 2004, with procurement of long-lead items for phase one of low-rate initial production (LRIP 1); this will involve a total of 12 aircraft, with the first delivery in 2008, subject to release of full funding in 2005.  Thereafter, three more LRIP batches are to be purchased, for delivery between the third quarter of 2007 and 2010, before the initial phase of full-rate production (FRP 1) is launched with long-lead items in 2007; this will be dependent upon full funding being approved in 2008, coincident with the JSF attaining IOC.  Production for the UK and USA (i.e. excluding export orders) will reach 13 aircraft per month in 2013, and the lines production capacity will be "considerably" greater than that.

Affordability is a key consideration for JSF and is dictating some compromises on the part of the different elements of the US armed forces in order to meet unit flyaway cost targets; in first quarter of 1997, all versions comfortably within or below specified cost, with the target prices (FY1997) being US$28 million for the CTOL version, US$35 million for the STOVL version and US$38 million for the carrier-capable version.  Subsequent statements have indicated FY2002 prices of $40 million, $45-50 million and $50 million respectively.

Following a request from Lockheed Martin, in October 2004 the Pentagon’s Defence Appropriations Board (DAB) approved a slip of about 12 months in the JSF development program, the first flight of the CTOL F-35A aircraft, moving from Fall 2005 to August 2006, and first flight of the STOVL variant to 2007. The DAB also approved a slip of 12 months for the commencement of low rate initial production (LRIP) of the JSF, now due to start in late 2007.  Lockheed Martin requested the slip so it could have more time to address weight issues on the aircraft, primarily in the STOVL F-35B model for the US Marines and UK. 

Michael Wynne, undersecretary of defense for acquisition, technology and logistics, announced on 1 June 2005 that he had cleared the JSF Joint Programme Office (JPO) to proceed with a revised timeline and updated acquisition strategy, but Pentagon officials decline to elaborate.

Wynne's approval allows the JPO to begin negotiations with Lockheed about revising the original $18 billion contract awarded in 2001, which covered a 10-year-long system development and demonstration (SDD) phase, excluding engine development.  The new contract is expected to add at least two years to the SDD plan and raise costs by $4-5 billion.   Details of the new schedule are still unclear, but the House Armed Services Committee (HASC) argues the JPO now wrongly plans to launch low-rate initial production (LRIP) in 2007, the same year in which the inaugural "weight-optimised" JSF aircraft is now scheduled to reach first flight.  The HASC inserted a provision that would force the JPO to delay LRIP launch until 2008.  The HASC provision, however, would probably delay the programme by another one or two years, which could add billions more in costs. Programme insiders also point out that the JSF design has been under development since 1995, so there is little risk of any major surprises surfacing after first flight in 2007.  Further, the LRIP aircraft are needed as training aircraft, and are not required to be in the weight-optimised design configuration.

F-35 Preferred Weapons System Concept 

While the Lockheed Martin JSF design has been refined since the beginning of development of the X-35 demonstrator, the basic design remains the same. The USAF CTOL variant defines a basis for the Lockheed Martin JSF family. The USN CV variant will have a larger wing and tail, giving it better range and carrier landing characteristics. The wing will feature folding wingtips. Of course, the CV variant will have stronger landing gear and an arrester hook.

The Air Force CTOL variant will have a refueling-boom socket behind the cockpit. The CV and STOVL variants will have an extendable refueling probe on the right side of the nose. The tricycle landing gear, with a forward retracting nosewheel and inward-retracting main gear, has single wheels on all assemblies in the CTOL and STOVL variants. The CV variant differs in having twin wheels on the nose gear.

The F-35's airframe makes heavy use of composite materials, with much work placed on reducing the cost of composite assemblies, which have traditionally been extremely expensive. In fact, the F-35 has been designed to be as cheap to manufacture as possible, using the latest computer-aided design and manufacturing tools. All flight controls are electric, in principle providing easier maintenance and greater combat survivability than hydraulic systems.

The production F-35 will be powered by a modified version of the P&W F119 designated the "F135". While it is as powerful as the original F119, it is much cheaper, as it uses lower-cost components at the expense of an increase in weight.

Although the P&W F119 engine was selected as the basis for the different engine options of the JSF, in 1995 the US Congress indicated a need for an "Alternate Engine" as a backup plan. The GE F120, originally designed for the F-22 Raptor program in competition with the P&W F119, was selected as the Alternate Engine, and refinements to the F120 for JSF are under development by a collaboration of GE, Allison, and Rolls-Royce.

The shaft-driven lift fan for the STOVL JSF is built by Rolls-Royce / Allison, and provides up to 8,150 kilograms (18,000 pounds) of lift thrust. The engine intake ducting is arranged in a "serpentine" fashion to eliminate radar reflections from the compressor blades.

The F-35 has two weapons bays, each of which can accommodate a single "Joint Direct Attack Munition (JDAM)" GPS-guided bomb and an AIM-120 Advanced Medium-Range Air to Air Missile (AMRAAM). The CV and CTOL variants will be able to carry two 900 kilogram (2,000 pound) JDAMS internally, while the STOVL variant will be limited to internal carriage of two 450 kilogram (1,000 pound) JDAMs.  The CV and CTOL variants have bulged weapons bays to accommodate the larger munitions.  The two bays have two doors each, with the AMRAAM fitted on a launch rail on the inner door.

Four stores pylons can be attached to all variants to provide a much larger warload at the expense of stealth. The inner pylon on each wing is rated for up to 2,270 kilograms (5,000 pounds), while the outer pylon is rated for up to 1,135 kilograms (2,500 pounds).

Only the USAF CTOL variant has a built-in gun, in the left wingroot.  Originally an "Advanced 27 Millimeter Cannon", an improved version of the Mauser BK-27 revolver-type cannon was preferred, but it has apparently been dropped in favour of a cheaper alternative, the 25mm GAU-12U 25mm.  The other variants do not have a built-in gun, but can accommodate a 20mm M61 belly mounted gun pod. 

The JSF will carry a sophisticated avionics suite. Northrop Grumman is working on the sensor suite for the Lockheed Martin F-35. The initial design assumption was that the JSF would be a consumer of sensor data, obtaining information from specialized intelligence-gathering aircraft, satellites, and other sources.  This approach promised to keep costs of the JSF down.

However, as the pieces began to fit together, something different emerged. This was partly due to the "bottom-up" realization that the new technologies being developed for the JSF were far more powerful than had been considered; and to the "top-down" realization that the numbers of expensive specialized intelligence-gathering aircraft would be small, while there could be thousands of JSFs.

Now the JSF is seen more as a producer of sensor data, with each aircraft interacting through high-speed data links with other aircraft to provide greater electronic domination of the battlespace.  If the other aircraft are JSFs, they will be able to cooperate to provide a capability greater than the mere sum of the parts.

The heart of the JSF's sensors will be the Raytheon "Multifunction Integrated Radio-Frequency System (MIRFS)", based on the APG-77 "active electronically scanned array (AESA)" developed for the Lockheed Martin F-22 Raptor.  The JSF's MIRFS will provide a range of functions, acting as a multimode radar, active jamming system, passive electronic defense system, and communications system. MIRFS will generate signals over a wide range of frequencies and pulse patterns in an unpredictable fashion to ensure "low probability of intercept", allowing the F-35 to "see but not be seen."

An AESA consists of an array of "transmitter-receiver (T/R)" modules linked by high-speed processors. Different T/R modules in the array can be allocated to different tasks, with more modules allocated to tasks that require greater power or sensitivity. The JSF's MIRFS will use improved technology compared to the F-22's APG-77, but airframe constraints mean that it will have fewer T/R modules, limiting it to about two-thirds the range (165 kilometers / 90 nautical miles) of the APG-77.

The F-35 will also be fitted with additional sensor systems, including a an "infrared search and track (IRST)" system for defense and air-to-air combat, and a targeting system for precision attack on ground targets.

The IRST system is known as the "distributed aperture infrared system (DAIRS or DAS)". DAS includes of six IR sensors mounted on different points of the fuselage to provide full-sphere IR detection and tracking. It will be able to identify and pinpoint both incoming missiles and airborne targets.

Targeting functions will be provided by the "electro-optical targeting system (EOTS)", featuring a forward-looking infrared (FLIR) imager, a CCD TV camera, a targeting laser, and a laser spot tracker. Unlike typical contemporary targeting systems, EOTS is not turret-mounted. It has a wide aperture that is blended into the aircraft's nose contours, covered by a window that is opaque to radar, and remains operational through the entire mission. It is derived from technology developed for the Lockheed Martin "Sniper" targeting pod.

Software will collect the inputs from all the sensors, as well as inputs relayed over a high-speed datalink, to provide sensor fusion and seamless data display.

The software will be executed on an "integrated core processor (ICP)". The ICP serves as a central "brain" for the aircraft, integrating all the other electronics systems and coordinating them for display to the pilot, and also executing the pilot's commands. This system is vitally important, since the JSF is a single-seat aircraft, and the pilot will need help to carry out his or her mission.

Northrop Grumman has selected a "commercial off-the-shelf (COTS)" processor system for the ICP. The JSF ICP is cheaper than the F-22's "Integrated Core Processor", which was designed a decade ago, but is an order of magnitude more powerful.

One of the functions of the central processing system is to provide "automatic target recognition and classification (ATRC)". It can often identify specific targets, and if it can't say exactly what a target is, it can at least show which targets are different.

The processing power of the JSF has presented the electronics system developers with a formidable software challenge. The F-22 Raptor uses about 2.5 million lines of software, but the JSF will use about twice that many. The JSF not only has a more advanced electronics system, but it must operate in both air-to-air and air-to-ground modes, and will be built in three different versions. The software is being designed in a modular or "layered" fashion to permit modification and growth.

The current plan is to have a comprehensive but minimal software suite for JSF operational introduction, and provide software updates to bring the JSF up to full operational capability. JSF electronics system designers hope to leverage off work done for the F-22 Raptor.

The pilot will receive inputs from the JSF's electronic systems using an advanced cockpit layout, featuring a full-panel-width display, with dimensions of 20 by 50 centimetres (8 by 20 inches), plus a secondary flight display array, along with "hands on throttle and stick" controls. It does not have a "head-up display", however, with this function taken over by a "helmet-mounted display" being developed by Visions Systems International, a collaboration of Kaiser Electronics and Elbit of Israel.

The "smarts" of the JSF will be particularly appreciated by pilots flying the STOVL version. Short takeoffs in the Harrier are a troublesome affair that require the pilot to have "three hands": one for the throttle, one for the stick, and the third for the lever that controls the direction of the Harrier's swiveling exhaust nozzles. A JSF pilot, in contrast, will simply fly the plane with stick and throttle, with the software handling the fine details of short takeoff.

While the Harrier has reaction control thrusters driven by engine bleed to provide low-speed manoeuvrability, the F-35 simply modulates the four-points of its vertical-lift system -- the pivoting exhaust, the two wing exhaust ducts, and the lift fan -- to provide control. This would be difficult or impossible to do under direct pilot control.

The X-35 prototypes are fitted with a Martin-Baker Mk.16E ejection seat. Production aircraft are supposed to use a new seat from the "Joint Ejection Seat Program".

JSF Requirements
(2004 estimates)



US Air Force 1,763 Multi-role (primary air-to-ground) fighter to replace the A-10 and F-16; and to complement F-22.   F-35A and F-35B variants.  IOC* 2012
US Navy 680 Multi-role stealthy strike fighter to complement F/A-18E/F. F-35C variant. IOC 2013
US Marine Corps Multi-role STOVL fighter to replace AV-8B and F/A-18C/D.  F-35B and possibly F-35C variants. IOC 2012
UK (Royal Navy and Royal Air Force) 150 Supersonic fighter to replace Sea Harrier FA.2 and Harrier GR.7/9.  F-35B variant. IOC  2014.



* IOC = Initial Operational Capability

Note that in June 2006 the JSF programme office revealed that the UK's buy has been reduced to 138 for sustainment and follow-on development (PSFD) memorandum of understanding now being negotiated for signature in late 2006.

(Above) Indicative LRIP schedule data

By December 2015, 12 aircraft a month for will be delivered to the USA, three aircraft a month to JSF partners, and up to seven aircraft a month would be available for export via the US Foreign Military Sales (FMS) programme.  The indicative LRIP schedule remains dependent upon final orders placed by partner nations, which will form a key element of the multi-nation production, sustainment and follow-on development (PSFD) memorandum of understanding now being negotiated for signature in late 2006.

The first JSFs will be built to Block 1 configuration, capable of carrying Boeing GBU-31 Joint Direct Attack Munitions (JDAMs) and Raytheon AIM-120 Advanced Medium-Range Air-to-Air Missiles (AMRAAMs). In 2011, Block 2 aircraft with increased capability will be delivered. And in late 2012, the first Block 3 JSFs that are fully compliant with the Operational Requirements Document (ORD) will be handed over.

Also by 2012, the USMC and USAF will have an Initial Operating Capability (IOC) with the JSF.  Under current plans, the US Navy and UK will reach IOC one and two years later respectively. 


Weight Problems

In late 2003 it became apparent that the F-35 aircraft, and in particular the STOVL F-35B variant was suffering from severe weight problems (3300lbs) that would seriously affect its performance and ability to meet key performance parameters.  Lockheed-Martin management finally recognised the seriousness of the problems and assigned a "Tiger Team" to address the issue.  In August 2004 JSF program officials said that they had identified 2,700 lb.(1,225 kilograms) in weight or weight equivalent reductions for the STOVL aircraft using strategies that include:

  • Reducing the distance between interior structural elements in the wing so the aircraft's exterior skin can be thinner.

  • Reducing the size of the weapons bays by 14 in. as well as the size of the vertical tails.

  • Rounding the shape, the loft line, of the fuselage behind the cockpit to hold more fuel. That was one of several changes that decreased drag.

  • Redesigning the electrical system to decrease the battery size and the amount of wiring.

  • Redesigning the wing-mate joint.

  • Rerouting some thrust from the roll post outlets to the main engine thrust.

Additional equivalent weight reductions will result from changing carrier operations requirements from those demanded for the Harrier including instrument flight patterns and vertical hover rate ratios.

The original empty weight of F-35B was 13,600 kg, and after the weight-reduction plan, it is about 12,420 kg now.

The weapons bay reduction will eliminate certain weapons from the STOVL configuration, including the Joint Standoff Weapon and 2,000-lb. bombs.  However, L-M  doesn't see that as an impediment to the proposed USAF buying  the STOVL variant aircraft.  Since USAF F-35B's will be dedicated to close air support it won't need large weapons, instead, it would likely carry 250-lb.-class small-diameter bombs.  Reportedly the UK, which in 2002 was delighted when L-M declared that the F-25B could have the same large weapons bay as the F-35A/C, is now less than happy about the change back - UK JSF aircraft will have to fulfil a far broader range of missions than USMC or USAF STOVL F-35's. 

The Lockheed Martin team also recaptured a 600-lb. equivalent reduction by redesigning the auxiliary inlet on top of the JSF's fuselage for better pressure recovery, said Tom Burbage, Lockheed Martin executive vice president and general manager for JSF. Predictions are that the changes will decrease takeoff roll by 100 ft., he said, and allow the bring-back weight for a carrier recovery to include two 1,000-lb. bombs, two air-to-air missiles and reserve fuel. Critical design review is slated for late 2005 with first flight of the production-configured aircraft in the summer of 2006 and funding for low-rate initial production to begin in 2007. Production in 2014-15 is expected to reach one aircraft per day.

Technical Performance

The original target performance specification and criteria specified for JSF were:


U.S. Air Force U.S. Marine Corps
U.K. Royal Navy
U.S. Navy
Variants Conventional Takeoff and Landing (CTOL) Short Takeoff and Vertical Landing (STOVL) Carrier-based (CV)
Unit Cost FY94$ $28M $35M $38M
Propulsion Baseline: Pratt & Whitney F119-PW-100 derivative from F-22 Raptor
Alternate Engine: General Electric F120 core
Empty Weight ~22,500 lbs ~24,000 lbs
Internal Fuel 15,000 lbs 16,000 lbs
Payload 13,000 lbs 17,000 lbs
Maximum Takeoff Weight

~50,000 lbs

Length 45 feet
Wingspan 30 feet 30 feet 36 feet (no wing folds)
Speed supersonic
Combat Radius  over 600 nautical miles
(with Internal fuel (design and overload) plus internal air-to-air and internal air-to-ground ordnance)
Crew one


A F-35 launching from an Invincible,
a sight that will now never be seen

These specifications are rather vague and demanding, the detailed target specification being secret.   However it is thought that the DoD and the JSF Project Office had to relax the specification (lower max speed, reduced combat radius, etc.) issued to the manufacturers in the final Joint Operational Requirements Document (JORD) in order to contain costs within the target costs.

The dimensions of the JSF STOVL variant were originally set by the maximum size of aircraft that the lifts of the Royal Navy's existing Invincible class carriers could accommodate.  However the UK no longer intends to operate the JSF from the Invincible-class, and by 1999 at the latest was no longer insistent on these dimensions.  Instead the UK plans to build a new class of aircraft carriers, designed specifically with JSF in mind.

In October 2003, the JSF performance parameters were as follows:

Key Performance Parameter U.S. Marine Corps U.S. Air Force U.S. Navy U.K.
Radio Frequency Signature Very Low Observable
Combat Radius 450 nm
USMC Profile
590 nm
USAF Profile
600 nm
USN Profile
450 nm
UK Profile
Sortie Generation 4 Surge
3 Sustained
3 Surge
2 Sustained
3 Surge
2 Sustained
3 Surge
2 Sustained
Logistics Footprint < 8 C-17 equivalent loads (20 PAA) < 8 C-17 equivalent loads (24 PAA) < 46,000 cu ft
243 ST
< 21,000 cu ft
102 ST
Mission Reliability 95% 93% 95% 95%
Interoperability Meet 100% of critical, top-level Information Exchange Requirements
Secure Voice and Data
STOVL Mission Performance
Short Take-Off Distance

Vertical Lift Bring Back


2 x 1K JDAM,
2 x AIM-120
With Reserve Fuel

450ft with ski-jump

2 x 1K JDAM,
2 x AIM-120
With Reserve Fuel

Maximum Carrier Approach Speed N/A N/A 145 knots N/A



STOVL Technology

The F-35B JSF STOVL variant will have a Rolls-Royce lift fan installed just behind the cockpit. This is driven by a shaft from the main engine, using a clutch to engage and disengage it. The two-stage, contra-rotating fan compresses air, which is then allowed to expand, producing thrust: it takes about 15 seconds for the fan to spool to full speed.


There is no combustion so the jet flow is cooler. The lift-fan thrust is balanced by that from the F-135 (derived from the F119) engine directed downward through a three-bearing vectoring nozzle and roll posts installed in the wing. The nozzle and roll posts are also from Rolls-Royce. Varying the thrust split between the lift fan and engine controls pitch.

Pros: The fan and engine produce more thrust than the engine alone, a technique used by the Harrier and Boeing X-32B demonstrator. 

Cons: The shaft spinning at high speed and the need for the clutch to engage and disengage the lift fan represent added complexity. The lift fan and nozzles are a dead weight during flight and they take up vital fuselage space which will be used for extra internal fuel tanks in the CV and CTOL variants, giving them a significantly longer range than the STOVL variant.



JSF Links

Note: Links open in new windows

Joint Strike Fighter Programme Office

JSF UK Industry Team

Lockheed Martin Aeronautics Joint Strike Fighter

Janes (The company's many publications are an excellent source of information on the JSF programme)




 © 2004-13 Richard Beedall unless otherwise indicated.