Lockheed Martin F-35 Lightning II
From Scramble - The Aviation Magazine
|Lockheed Martin F-35A Lightning II|
|Crew||1 (in Martin-Baker US16E ejection seat)|
|First Flight||December 15, 2006 (F-35A AA-1)|
|Entered Service||IOC planned for 2013|
|Number built||in production|
|Length||15.37 m||50.43 ft|
|Wingspan||10.65 m||34.94 ft|
|Height||5.28 m||17.32 ft|
|Wing area||42.7 m²||460 ft²|
|Empty||13,302 kg||29,300 lb|
|Internal fuel||8,278 kg||18,250 lb|
|Maximum takeoff weight||27,200 kg||59,966 lb|
|Capacity||18,000 lbs weapons payload|
|Engines||one Pratt & Whitney F135 turbofan engine|
|Thrust||178 kN+ (each)||40,000+ lbf (each)|
|Maximum speed||1,093 km/h||1,200 mph|
|Combat radius, internal fuel, with two 2,000 class bombs and 2 AIM-120 AAMs carried internally||1,111 km||590 nm |
|Service ceiling||15,240 m||50,000 ft|
|Rate of climb||m/min||ft/min|
|Avionics||Northrop Grumman AN/APG-81|
|Armament||One General Electric GAU-12 Equalizer 25 mm gun; air-to-air: AIM-9X Block II and AIM-120 AAMs; air-to-ground: JDAM, Paveway, SDB and WCMD series PGM, B61 Mod 12 nuclear weapon.|
The F-35 Lightning II is a fifth generation multi-role fighter under development to perform ground attack, reconnaissance, and air defense missions with stealth capability. The F-35 has three main models: the F-35A conventional takeoff and landing variant, the F-35B short take off and vertical-landing variant, and the F-35C carrier-based variant. The F-35A is scheduled to replace US Air Force and international F-16, the F-35B will replace US Marine Corps and Royal Air Force AV-8B Harrier IIs and the F-35C will replace US Navy, Royal Canadian Air Force and Royal Australian Air Force F/A-18A/B/C/D Hornets.
Main requirements for the F-35A were 600 nm combat range carrying two 2,000 class bombs (such as the GBU-31/B JDAM) and two AIM-120 missiles internally, ensuring the stealth characteristics. Generally speaking, this is comparable to the range/payload of a F-16C Block 50 with two external fuel tanks ans similar external weapons, of course making the F-16 non-stealthy. As a result, the F-35A is a fairly large and heavy aircraft: its 13 tons empty weight is comparable to that of the F-15C Eagle and nothing near the F-16C-CF-50s 7,5 tons. Equally, the F-35B has double the (empty) weight compared to the from the Harrier II (13,600 kg vs. 6,340kg). This results in considerable jet blast and water spray, as can be seen here. Main requirement for the F-35B is a combat radius of 450 nm on internal fuel and while carrying 2x 1,000 lbs class weapons (such as the GBU-32/B JDAM) in the weapons bay. This is significantly lower than the 590 nm Hi-Lo-Hi combat radius of the (non-stealthy) AV-8Bs carrying a 3,500 lbs weapons load. To put things in perspective: the `maximum combat range' of the F-15E is quoted as 1,853 km (1,000 nm) . In March 2012, the US Air Force agreed to relax the minimum combat range requirement to 583 nm, 17 nm below the initial requirement. The range was reduced after Pratt & Whitney diverted more bleed air from the F135 powerplant for cooling purposes, as the engine was running hotter than expected. The US Air Force also accepted new estimates that reduced the F-35A's fuel capacity and added the weight and drag of the Lockheed electro-optical targeting system. Another key performance parameter is the sortie rate. The B-model is required to generate four sorties per day, the A and C models are only required to generate three sorties per day.
Avionics and systems
The F-35 is fitted with an impressive avionics suite. Primary sensor is the Northrop Grumman AN/APG-81 AESA radar, BAE Systems AN/ASQ-239 EW system (derived from the AN/ALR-94 suite fitted to the F-22), Elbit/Rockwell HMDS, Lockheed Martin AAQ-40 E/O Targeting System (EOTS) and Northrop Grumman AN/AAQ-37 Distributed Aperture System (DAS), providing missile and aircraft detection, tracking and warning. Like the F-22. the F-35 uses sensor fusion, of which the integration of the AN/APG-81 radar and the AN/ASQ-239 EW system is a perfect example. Because the advanced HMDS, the F-35 is not fitted with the usual HUD. New key avionics item is the Harris Corporation Multifunction Advanced Data Link, which provides secure data-linking technology between stealth aircraft such the F-22 and B-2. A major innovation is the Honeywell IPP. The F-35 is one of the first "more-electric aircraft", meaning it uses electricity to replace several functions formerly fuelled by hydraulics or pneumatics. The 200 hp IPP provides engine start power, on-board cooling and emergency power. Harris Corporation delivers the avionics infrastructure for the radar and Integrated Core Processor Electronics (ICP) and fibre-optic network solutions and power supplies.
For the F-35A (excluding the F135 engine), the target price was $221.2 Mio (LRIP-1), $161.7 Mio (LRIP-2) and $128.2 Mio (LRIP-3). In July 2011, the US Air Force F-35 programme office confirmed the estimated cost overrun for the LRIP-1 to LRIP-3 aircraft is roughly $1.15 billion. The higher figure includes the roughly one-third share of the overrun absorbed by Lockheed Martin and Pratt & Whitney. The US government has to pay the remaining $771 million in extra costs under the terms of the first three lots of LRIP. Under the terms of the LRIP 4 contract, Lockheed Martin and the Pentagon share any costs above the ($111.6 Mio excluding the engine) target price 50:50, with a ceiling on what the government would have to pay of 120%. So an F-35A could cost the DoD up to $133.9 million (excluding engines). Beyond that Lockheed Martin carries the cost. A single F119 engine is quoted to cost approx. $ 20 Mio, taking the minimum LRIP-4 unit cost price tag to approx. $132 Mio. Therefore, the F-35 is under constant threat to be delayed or even cancelled due to the cost overruns.
F-35 development time takes longer then expected. These are caused by technical setbacks, as well as funding issues. Several potential F-35 operators are considering to order or upgrade 4th generation fighters in order as a gap-filler measure until the F-35 has reached IOC. The Royal Australian Air Force already ordered 24 F/A-18F Super Hornet aircraft (and considering acquiring additional ones), while the US Navy basically faces the same problem. The US Air Force is considering to upgrade late model F-16C Block 40/50 aircraft while waiting for the arrival of the F-35. Several potential international customers are examining alternatives, driven by the escalating unit price and delayed time schedule. To make things worse, the US Air Force launched a service life extension study for its F-15E fleet, where it widely assumed the US Air Force would replace the F-15E with the F-35A.
Some observers feel that the F-35 is over optimized to prevent detection by fighters and tracking radars in front of it, it lacks the maneuverability and SEP in air-to-air combat . The wing loading of the F-35A is quite high (approx. 20% higher than F-16C, MiG-29M and Su-27/Su-30) making it less agile and requiring a higher thrust to a given turn radius and speed. The thrust loading is significantly inferior to the F-15, F-16, F-22, MiG-29M and Su-27/Su-30, resulting in slower acceleration, slower climb, more energy bleed in tight turns. To make matters worse, early 2013 the US Air Force lowered the performance bar for sustained turn rate and acceleration. The specifications for all three variants pertaining to transonic acceleration and sustained turn rates have been reduced:
• increased time for acceleration from 0.8 Mach to 1.2 Mach by at eight seconds
• reduced sustained turning performance from 5.3g to 4.6g
• increased time for acceleration from 0.8 Mach to 1.2 Mach by at 16 seconds
• reduced sustained turning performance from 5g to 4.5g
• increased time for acceleration from 0.8 Mach to 1.2 Mach by at least 43 seconds
• reduced sustained turn performance from 5.1g to 5.0g
Having a maximum sustained turn performance of less than 5g is the equivalent of an F-4 Phantom II or an F-5. All three variants are having problems with their horizontal tails, experiencing higher than expected temperatures during sustained high‑speed / high‑altitude flight, resulting in delamination and scorching of the surface coatings and structure.
The F-35 has continued the move away from high-maintenance coatings, with a greater use of durable, low-maintenance structural materials. Even so, the F-35 reportedly has a RCS of around 0.00143 m², which is about 7 to 9 times bigger than the minimal frontal RCS of the F-22 Raptor, but 1/35 to 1/70 of the frontal RCS of the western 4th+ Generation fighters such as Typhoon, Dassault Rafale and F/A-18E/F. To put things further in perspective, the F-35 stealthiness is a bit better than the B-2 Spirit bomber, which, in turn, was twice as good as that on the even older F-117 Nighthawk. Unlike the Raptor, the F-35’s stealth is primarily directed at radars in front of it, especially X- and upper S-band systems used by fighters, SAMs, and tracking radars, and, to a lesser extent, L-band surveillance systems , making it stealthy for head on detection only . Furthermore, new 'counter stealth radars' are being developed. These new radars operate in low bandradars, especially operating in the VHF band. While the F-35 is frequently criticized for the limitations of its stealth capability in the mid and upper microwave bands, the compact size of this aircraft makes it highly susceptible to detection by these low band (VHF) radars, unlike larger aircraft such as the B-2A Spirit.
F-35A/B forward root rib
Thirty F-35A and 34 F-35B airframes built early in the aircraft's production run will require modification to achieve their full 8,000-flight-hour design lives. That's because program engineers identified a shortfall with a structural component in their wings, known as the forward root rib. It's an aluminum part located where the leading edge of the wing meets the strike fighter's fuselage. The engineers came across this issue initially during an analytical assessment of the F-35 airframe's fatigue life. The new modified forward root rib design will be incorporated into production planes from the beginning of Low Rate Initial Production (LRIP) Lot 5 for both CTOL and STOVL aircraft. The F-35C is not affected by this issue.
F-35B bulkhead 496
In November 2011, after sea trials on-board the USS Wasp, three of the five developmental F-35Bs have developed tiny cracks in a lift fan-related component which prevent the flight-test aircraft from reconfiguring in flight and landing vertically. The potential for cracks to develop in the actuator support beam was revealed several years ago when the Alcoa-supplied 496 bulkhead in the rear fuselage of the F-35B cracked unexpectedly only 10% through the durability test cycle. Subsequently, it was revealed in 2014 that cracks on the F-35B primary support structure were more extensive than previously thought. The initial cracks were found late 2013 on section 496, a primary wing carrythrough bulkhead, prompting officials to stop the ground-based testing at hour 9,400 during the second life’s worth of use — or second 8,000 hr. of equivalent flight hours — to investigate the issue. Since then, cracking also has been discovered on adjacent bulkheads.
F-35B/C Transonic roll-off and buffeting
Meanwhile, the F-35B and C variants continue to have issues with transonic roll-off and buffeting. On the F-35B, the program introduced vehicle systems software to reduce rudder and flaperon hinge moment in the transonic/supersonic region. Moreover, in December 2012 after multiple cracks were found in a F-35B bulkhead flange on the underside of the fuselage during the 7,000-hour inspection.
No alternative engine
As early as August 2007, there have been issues with the IPP. In 2007, an IPP shut down on the integrated test stand. The test stand was damaged as a result of the shut down and had to be refurbished. Stator and rotor clearance issues within the IPP have been identified as the root cause. Honeywell redesigned the IPP and the first redesigned model was delivered October 2007. However, SDD flight operations were suspended on August 2nd 2011 and the US Air Force safety oversight board launched an investigation after conventional take-off and landing flight test aircraft AF-4 experienced an "explosive event" during a routine ground test. A control valve malfunction caused the IPP to fail after starting up the F-35's engine. The IPP is used to start the engine, and then powers the system that cools the F-35's power supply. Flights were resumed August 23rd 2011. Another concern is damage the (carriers') flight deck. In March 2010, the GAO reported that exhaust from the engine and integrated power package exhaust may cause excessive damage to the flight deck environment and runway surfaces that may result in operating limits or drive costly upgrades and repairs of F-35 basing options.
F-35 noise levels that are reportedly up to two times louder than the F-15 fighter, and close to four times louder than an F-16. This issue has forced a delay in critical approvals for Eglin AFB, and has also become an international concern. With respect to perceptions of loudness, every 10 decibels will double apparent volume, so a 10-decibel difference is about 2x as loud, a 19-20db difference is 4x as loud, and a 30db difference would be about 8x as loud.
The US Marine Corps has expressed concerns about the security of the Autonomic Logistics Information System (ALIS). The ALIS system has both a classified and unclassified node in the same system. The unclassified part of the system deals with maintenance information, the classified side of the ALIS system deals with mission planning for the pilots who will fly the aircraft. As a temporary solution, the classified and unclassified systems were separated. As of November 2012, the US Marine Corps does not yet have a definitive date as to when it expects the work to be completed.
In November 2011, a study team found the following 13 areas of concern remained to be addressed in the F-35:
- The helmet mounted display system does not work properly (a new ' Gen3' helmet will start flight tests in 2014).
- The fuel dump subsystem poses a fire hazard.
- The Integrated Power Package is unreliable and difficult to service.
- The F-35C's arresting hook does not work (a redesigned tailhook started flight test December 2013).
- There are classified "survivability issues", which have been speculated to be about stealth.
- The wing buffet is worse than previously reported.
- The airframe is unlikely to last through the required lifespan.
- The flight test program has yet to explore the most challenging areas.
- The software development is behind schedule.
- The aircraft is in danger of going overweight or, for the F-35B, too nose-heavy for VTOL operations.
- There are multiple thermal management problems. The air conditioner fails to keep the pilot and controls cool enough, the roll posts on the F-35B overheat, and using the afterburner damages the aircraft.
- The automated logistics system does not work properly.
- The lightning protection on the F-35 Lightning II is uncertified, with areas of concern.
System Development and Demonstration
While the actual JSF development contract was signed on 16 November 1996, the contract for System Development and Demonstration (SDD) was awarded on 26 October 2001 to Lockheed Martin, whose X-35 beat the Boeing X-32. Although both aircraft met or exceeded requirements, the X-35 design was considered to have less risk and more growth potential. The 10-year SDD phase involves the development and testing of the entire aircraft system, including its manufacture. During SDD, the team will build a total of 19 test aircraft. Fourteen will undergo flight-testing, seven will be used for non-airborne test activities, and one will be used to evaluate the F-35’s radar signature. Nine nations are partnering in the F-35’s SDD phase with participation varying in three tiers. Tier 1 countries are the United States and the United Kingdom, the latter contributing 10% of the development costs. Tier 2 countries (Italy, the Netherlands) will contribute around 5% each. Tier 3 participants (Turkey, Canada, Denmark, Norway and Australia) will each contribute between 1% and 2%. Participating countries receive industrial orders and royalties for non-partner sales. Singapore and Israel are “Security Cooperation Partners”.
Initial Operational Test & Evaluation
Tier 1 and 2 countries can participate in the Initial Operational Test & Evaluation (IOT&E) phase. So far, the United States, United Kingdom and the Netherlands signed for the IOT&E phase.
Production Sustainment and Follow-on Development
This phase covers the follow-on development of the F-35 for its entire operational career. Late 2006, all participating countries signed the MoU for the PSFD phase.
The top two industrial partners on the airframe portion of the program are Northrop Grumman (which provides the completes centre fuselage, delivering the 50th centre fuselage 17 August 2011) and BAE Systems (which provides the rear fuselage and horizontal and vertical tail planes). The structure is transported to Lockheed Martin's Fort Worth final assembly. It then is integrated with the other major sections including the Lockheed Martin produced forward fuselage, cockpit and wings, Pratt & Whitney supplied engine and Northrop Grumman supplied radar and sensor suite. The F135-PW-600 engine for the F-35B, equipped with unique Shaft Drived LiftFan® (SDLF) gearbox and 3 Bearing Swivel Nozzle (3BSN), is developed in cooperation with Rolls-Royce. The development of the General Electric F136 alternate engine (like the F110 was for the F100), ended the contract with General Electric, leaving the F-35 program with a sole engine supplier.
Low Rate Initial Production
In order to compensate for the constant cost overruns, the DoD aanounced in 2011 it will reduce significantly the number of airframes to be included in LRIP-5 and beyond. Early 2012, the DoD said it will delay U.S. orders for another 179 jets until after 2017, bringing the total number of US F-135s delayed to over 400.
July 2007, LRIP-2 contract for six F-35A aircraft.
The LRIP-4 included 32 aircraft, including four F-35C, 15 F-35B (including one for the Royal Air Force) and 13 F-35A aircraft, the latter including a second F-35A for the a single F-35A for the RNethAF. Loaded with Block 2A software. LRIP-4 was the first Fixed Price Incentive Firm Target contract for the F-35. Previous batches had been cost-plus.
In November 2012, LRIP-5 for 32 aircraft was contracted. Loaded with Block 2A software. For LRIP-5, Lockheed Martin will build 22 F-35A, three F-35B and seven F-35C aircraft. Originally, LRIP-5 was supposed to include 47 aircraft.
Originally 80 planned, LRIP-6 (contracted September 24th, 2013) eventually includes 36 aircraft (23 F-35A (including three for Italy and two for the Australia), six F-35B, 7 F-35C. Loaded with Block 2B and - later - 3i software.
LRIP-7 was also contracted September 24th, 2013 and includes 35 aircraft (24 -A, 7 -B, 4 -C). Included in the contract are parts for three F-35As for Italy and two F-35As for Turkey. These are also provisions for one STOVL jet for the UK. Loaded with Block 2B and - later - 3i softwae. Originally, Lot 7 was expected to contain 77 aircraft. Unit cost of LRIP-7 aircraft is 6% lower than LRIP-5 aircraft and are specified by Lockheed Martin as $98 million for the 24 F-35A, $104 million for the F-35B and $116 million for the F-35C aircraft. All prices are excluding the engine, which is contracted separately with Pratt & Whitney.
Initially planned to be a 90 aircraft lot, LRIP-8 is now expected to contain 45 aircraft, including 19 F-35As for the US Air Force, six F-35Bs for the US Marine Corps, four F-35Cs for the US Navy, four F-35Bs for the United Kingdom, four F-35As for Japan, four F-35As for Italy, two F-35As for Norway and two F-35As for Israel. To be loaded with Block 3F software.
Full Rate Production
FY2015, 1st Full Rate Production (FRP-1) batch, expected to contain 107 aircraft.
Conventional take-off and landing (CTOL) version under development for United States Air Force and various international customers, powered by F135-PW-100 engine and stressed for 9g manoeuvres. The F-35A uses standard runways for take-offs and landings. Internal fuel capacity is 18,250 lbs, providing an combat radius (internal fuel, 2x 2,000 lbs class bombs, 2x AIM-120) of 590 nm. F-35A carries a 25 mm GAU-22/A cannon internally. The standard internal weapons load is two AIM-120C air-to-air missiles and two 2,000-pound GBU-31/B JDAM guided bombs. Optional internal loads include eight GBU-39 Small Diameter Bombs, as well as a wide variety of air-to-ground missiles, dispensers and guided weapons, including the B61 nuclear weapon and (in Norwegian service) the Kongsberg Joint Strike Missile.. The internal weapons bay is reconfigurable for all air-to-ground ordnance, all air-to-air ordnance or a blend of both. When stealth is no longer required to execute a mission, the F-35A external pylons are loaded with ordnance, giving the aircraft a weapons payload of 18,000 pounds.
Short-takeoff/Vertical-Landing (STOVL) version under development for US Marine Corps and Royal Air Force, powered by F135-PW-600 turbofan engine with Rolls-Royce LiftSystem®, consisting of a Liftfan® and 3 Bearing Swivel Module (3BSM) swivelling exhaust. Internally, two 1,000 lbs bombs can be carried (compared to 2x 2,000 lbs in case of the F-35A/C), due to the somewhat smaller bomb bay dimensions. The reasons for this is the complex propulsion system with the large Liftfan® just behind the cockpit. With 13,500 lbs, the internal fuel capacity is also smaller, providing an unrefuelled combat radius of 450 nm (internal fuel and 2x 1,000 lbs class bomb) . A version of the 25 mm GAU-22/A cannon is pod mounted. The F-35B is stressed for 7.0g manoeuvres. Primary customers were be the US Marine Corps, the Royal Air Force/Royal Navy and the Italian Navy, although the UK announced a switch to the carrier capable (and less expensive) F-35C. First supersonic flight (to Mach 1.07 at 30,000ft (9,150m)) was reached on 10 June 2010.
Carrier based (CV) version under development for United States Navy, powered by F135-PW-400 turbofan engine, stressed for 7.5g and strengthened landing gear (constructed from Aermet 100 steel and with twin nose-wheel gear) to allow carrier operations and (compared to the F-35A) 22% bigger wing to allow lower approach speeds. F-35C internal fuel capacity is nearly 19,750 lbs, providing an combat radius of greater than 640 nm (same conditions as stated in the F-35A section). With twice the range on internal fuel as the F/A-18C Hornet, the F-35C achieves much the same goal as the F/A-18E/F Super Hornet. First flight was 8 June 2010.
Designation for initial System Development and Demonstration airframes.
Initial F-35s are flying with Block 0.1 vehicle management system software.
Interim avionics and software standard, rolled out on January 22nd, 2009 in F-35B c/n BF-4. This software only supports training and test support activities.
Development standard with only basic capability, i.e. to support the JDAM and AIM-120 AMRAAM. Block 1 software for the mission system was first flown on the 737-based Cooperative Avionics Test Bed (CATBird) mid 2010. One a/c ordered by the Royal Netherlands Air Force to participate in the Initial Operational Test & Evaluation (IOT&E) phase. Block 1B software was installed mid 2012.
Software block fitted to LRIP4 aircraft. Lockheed Martin flew the first test flight with Block 2A software on March 2nd, 2012 and the 1st aircraft was delieverd May 6th 2013. The Block 2A configuration adds new functionality to the F-35. The aircraft was previously only able to operate three of its six Northrop Grumman AN/AAQ-37 electro-optical distributed aperture system DAS infrared cameras. The Block 2A has all six cameras installed and operative. Additionally, the Block 2A is cleared to turn on the Lockheed Martin electro-optical targeting system (already installed in the Block 1B but not cleared to operate). Finally, the initial Block 2A software release adds a weather radar mode. Block 2B software, released for flight test in February 2014 and available to the F-35 fleet mid 2015, is the “initial warfighting” software that adds sensor capabilities missing from the training software releases, plus the AIM-120 AMRAAM air-to-air missile, GBU-12 laser-guided bombs and the GBU-32 JDAM.
Final standard in the System Development and Demonstration phase, scheduled to be completed in 2017. Block 3i (Interim) is the Block 2B software rehosted on newer avionics hardware. Block 3F (Final) adds weapons such as the AIM-9X and AGM-154 JSOW, and sensor capabilities such as full radar synthetic aperture radar mapping (SAR), plus expansion of the flight envelope.
Enhanced version. Upgrades include increased airframe life, improved power/thermal management, Multifunction Advanced Data Link and Link 16 datalink, JSOW Block 3, AIM-9X Sidewinder Block II, B61 and Joint Strike Missile (Norwegian aircraft) integration. Expected to be released by 2019. The FY2014 budget request shows that B61-12 integration is scheduled for Block 4A and Block 4B aircraft in 2015-2021 with full operational capability in 2022 – three years after the first B61-12 is scheduled to be delivered.
Enhanced version, with range and propulsion improvements, electronic attack functions, Blue Force Tracking, all-aspect passive threat detect/response management.
Block 7 will introduced improved protection against biological/chemical warfare threats.
- October 2001: SDD contract awarded
- December 2006: 1st flight F-35A
- June 2010: 1st flight F-35C
- 2012: DoD announced to slow down F-35 production
- April 2012: 1st Klu F-35A rolled-out
- December 2015: planned IOC date of US Marine Corps F-35B loaded with Block 2B software
- December 2016: planned IOC date of US Air Force F-35A loaded with Block 2B software
- US Air Force (1,763 -A planned)
- US Navy (260 -C planned)
- US Marine Corps (340 -B and 80 -C planned)
- Royal Air Force/Royal Navy (138 -B planned)
- Royal Canadian Air Force (65 -A planned)
- Royal Australian Air Force (approx. 100 -A planned)
- Royal Danish Air Force (48 -A planned)
- Italian Air Force (69 -A + 62 -B planned)
- Japanese Air Self Defense Force (42 -A planned)
- Royal Netherlands Air Force (37 -A planned)
- Israel Air and Space Force (100+ -A planned)
- Royal Norwegian Air Force (52 -A planned)
- Turkish Air Force (approx. 100 -A planned)
- Republic of Singapore Air Force (approx. 100 -A planned)
- South Korea (40 -A planned)
Estimated production run: approx. 3,400
Longer term prospects:
F-35A in formation with F-16B
First flight Klu F-35A
- Lockheed Martin
- Wikipedia English
- Defense Media Network: Commemorating first flight
- Defense Media Network: Commemorating first delivery
- Lockheed Martin website
- JSF News, Dutch JSF/F-35 Site
- Air International May 2011
- ^ Lockheed Martin website August 17, 2011
- ^ Global Security website, 18 October 2011
- ^ Rand Corporation, Project Air Force, Air Combat Past, Present, Future, August 2008
- ^ Flightglobal 30 January 2013
- ^ f-16.net forum
- ^ Tracking the development of anti-stealth countermeasures
- ^ Air Force Magazine, September 6, 2011
- ^ Department of Defense, F-35 JSF Concurrency Look Review, November 29, 2011
- ^ Air International, December 2010
- ^ Air International, December 2010