Development

The JSF Concept Demonstration phase was relatively straightforward. Although the X-35s were aerodynamically representative of the planned production configuration, they lacked operational equipment, and stealth materials and structure were not incorporated, so the System Development and Demonstration phase was always likely to be more difficult.

The development effort was to be carried out with an initial batch of 22 aircraft, 14 flying and eight for ground tests, operating from Edwards AFB and NAS Patuxent River. About 6000 hours were to be flown.

The programme's low-cost assumptions began to be undermined. Originally JSF was to be mainly a consumer of data generated by other platforms like the F-22, E-3 and E-8. But it was recognised that JSF could be a useful contributor of data as well, but for this it would need sophisticated onboard sensors and high-speed datalinks, all of which cost money. The aircraft's air-to-air capabilities were fairly modest, as the F-22 would be carrying out that mission. But export customers would need better air-to-air performance as they mostly wouldn't have a dedicated air superiority fighter.

In the summer of 2002 Lockheed Martin released what it called a 'finalised' design for the production JSF. This closely resembled the X-35, with only minor changes to its shape. Despite the fact that major changes were not required, and Lockheed Martin was able to piggy-back on the F-22 development effort, development costs were estimated to have increased by 80%.

Although the aircraft completed a Preliminary Design Review in April 2003, the Critical Design Review was postponed until February 2006, the aircraft's first flight slipped to August 2006, and low-rate initial production was put off until 2007.

The main problems with development centered on the STOVL version, which basically was carrying too much weight with an underpowered engine. Smaller internal weapons bays were put in, which cut the aircraft's payload to a pair of 1000lb weapons internally. Eventually the aircraft's weight was reduced by 2700 lb (1225 kg), while propulsion efficiency was improved and drag reduced. This alone added about $5bn to the development budget.

The first CTOL aircraft began final assembly in May 2005. It was rolled out on February 19th 2006 at Fort Worth, Texas. The aircraft underwent extensive ground testing in the autumn of 2006. On September 15th 2006 the first engine run of the F135 turbofan was conducted in an airframe, with the tests completed on September 18th after a static run with full afterburner. The engine runs were the first time that the F-35 was completely functional on its own power systems. It made its first flight at Fort Worth on December 15th 2006.

F-35 chief pilot Jon Beesley was at the controls for the 35 minute flight. The aircraft was flown to 15,000ft (4,600m) and 225kt (415km/h) with the landing gear down, then slowed to approach speed. The test plan then called for the gear to be retracted, but there was a small sensor anomaly (a mismatch in the air data system) and mission rules required the aircraft to land. The faulty probe was replaced and calibrated with a 110kt taxi test.

AA-1 made its second flight on January 8th 2007. Approximately 10 minutes into the flight, CTP John Beesley retracted the landing gear and climbed from 15,000 to 20,000 feet to evaluate handling qualities and engine operation in the cruise mode at Mach 0.6 (450 mph) and Mach 0.7 (530 mph). The handling tests included rolls, turns, angle-of-attack changes and engine throttle changes. The flight lasted 62 minutes and was executed exactly as planned.

The third flight began with a military (non-afterburning) power takeoff. On flight 4, low-altitude manueuvering was tested.

On January 24th 2007 Pratt & Whitney�s F135 engine exceeded 7,000 system design and development (SDD) ground test hours. This achievement, in addition to the 3,600 test hours accumulated during the F-35 concept demonstration program, puts the total engine test program hours logged at more than 10,000.

On January 31st 2007 the F-35 successfully completed its first test of the F135's afterburner. The test occurred during the F-35�s fifth flight when the aircraft climbed to 20,000 feet and flew in maximum afterburner for six seconds with all augmentor zones lit.

On flight 6 a fuel dump test was carried out. Flight 7 evaluated the operation of the speed brake. The F-35 doesn't have a dedicated speed brake - instead the flight control software deflects control surfaces (leading and trailing edge flaps and rudders) to slow the aircraft.

On May 4th 2007 Pratt & Whitney and Rolls-Royce successfully completed the first phase and initiated phase two of the F135 short-takeoff/vertical-landing engine LiftFanďż˝ gearbox qualification test at the Rolls-Royce facility in Indianapolis, Indiana.

The high-technology gearbox is a critical component that allows the F-35B to achieve the aircraft's vertical takeoff capability. The test includes a three-step process with the LiftFanďż˝ gearbox ultimately being operated 30 percent above maximum operational requirements. The test will be used to evaluate and validate the current lightweight gearbox design at the specification thrust rating for the life of the F135 propulsion system.

On AA-1's eighth flight a software fix for the air data anomaly seen on flight 1 was flown. This flight was cut short because the chase aircraft had a mechanical problem. The first afterburner takeoff was performed on flight 9. This flight lasted for 90 minutes. The aircraft was flown to 16° AOA at 20000ft.

Pratt & Whitney�s F135 engine powered three F-35 Lightning II flight tests on April 26th and 27th 2007, marking the first time the F-35 Lightning II has completed more than one flight test in 24 hours, and three flight tests in less than 48 hours.

On flight 10 the helmet-mounted display(HMD) was flown for the first time. This mission included 360° rolls, snap engine transients in afterburner, and close formation flying.

Flight 11 involved several lower altitude maneuvering blocks , and well as maneuvering with the speed brake.

On flight 12 the aircraft was flown by Jeff Knowles. On flight 12 Jon Beesley took the aircraft to 30000ft, performed a touch-and-go landing, flew at 17° AOA and cycled the air refuelling door.

On June 12th 2007 Pratt & Whitney and Rolls-Royce completed the last of the three-step gearbox test which validated the gearbox design and demonstrated expected engine performance at all required thrust levels for the F135 short-takeoff/vertical-landing (STOVL) propulsion system.

On its 19th test flight in early May the first prototype suffered a brief power failure, which was caused by a short in the F-35's 270V power system when a lead inside a box touched the lid. The power-by-wire flight-control system locked the affected surface - the right horizontal stabiliser - and adjusted the authority on the other control surfaces to compensate. Lockheed launched a a complete audit of the aircraft's electrical system following this incident.

While the aircraft was on the ground it underwent scheduled upgrades, adding additional instrumentation, including inlet rakes, and doing additional proof testing, including the refuelling receptacle. The first release of prognostic health management software was being loaded, plus upgrades to the flight control software resulting from the first 19 flights.

Lockheed has begun final assembly of the second JSF, and the first F-35B short take-off and vertical landing variant. Mating of the major airframe sections began in June 2007 at Fort Worth, Texas and the aircraft is scheduled to roll out in December and fly in May 2008. The aircraft, BF-1, is the first with the "optimised" airframe redesigned to reduce weight.

Pratt & Whitney announced on August 1st 2007 that the F135 engine had exceeded 8000 ground test hours in the SDD phase of development.

On August 8th 2007 P&W announced that a series of crosswind validation tests for the F135 STOVL engine had been completed at its test facility in West Palm Beach, Florida. A Pratt & Whitney Canada PT-6 turboprop engine was used to simulate crosswinds of up to 35 knots (40 mph) across the inlet of the lift fan as the F135 propulsion system simulated flying in STOVL mode at power settings up to full power.

On August 13th 2007 Northrop Grumman delivered the initial release of software required to perform manufacturing checkout of the first F-35B to Lockheed Martin. The company has delivered software modules needed to perform three critical functions: functional test of key sensor subsystems such as radar, electronic warfare, and communication/navigation/IFF; download of maintenance information from the aircraft; and in-flight detection and pilot notification of safety-critical faults.

On September 24th 2006 the GE Rolls-Royce Fighter Engine Team announced that it successfully fired the afterburner on the F136 test engine for the first time. Turbomachinery checkout testing will continue in Cincinnati prior to the engine being shipped to Arnold Engineering Development Center in Tennessee to simulated altitude testing. Presently, the turbomachinery components are being validated in original F136 prototypes built by the Fighter Engine Team before the Development and Demonstration (SDD) program was formally launched in August 2005 with a $2.4 billion contract award. Using a pre-SDD prototype allows risk-reduction testing to be conducted at lower cost.

Completion of these key tests will support the Critical Design Review (CDR) in early 2008, conducted by the Joint Strike Fighter program office. During that review, every aspect of the engine design will be analyzed and evaluated in order to proceed with the building of the first full product configuration engines.

The first product configuration engine in the SDD program is expected to test in early 2009, followed by the first flight on the F-35 Lightning II aircraft in 2010.

On September 24th 2006 BAE Systems announced that acceptance testing for the F-35 Lightning II electronic warfare (EW) suite spiral release 2 had been completed. This spiral release provides the capabilities to perform initial manufacturing system checkouts on F-35 BF-4, the first full avionics aircraft, scheduled to fly in the first quarter of 2009.

On October 9th 2007 AA-1 carried out its first ground run since its 19th flight was cut short by an electrical incident. Issues with electical power supplies, the integrated power package, flight-control actuators and the F135 engine combined to keep the aircraft grounded for longer than expected.

Interruption of the May test flight, caused by arcing within electrical units in the 270V power system, has been tackled by increasing separation between wiring and casings. The JSF joint programme office (JPO) says AA-1 will return to flight with reworked and requalified "Dash 9" units and switch to redesigned "Dash 10" units as they become available.

An issue with the integrated power package (IPP), which combines auxiliary and emergency power units and environmental control system, was discovered during laboratory testing. Honeywell delivered a replacement IPP to Lockheed on October 17th after the unit had been disassembled and rebuilt to verify proper permanent-magnet rotor-to-stator clearance.

The non-flightworthy IPP in the aircraft was used for the initial ground runs, allowing aircraft system leak checks, flight software check-out and transition between normal and emergency power.

Lower than expected fluid reservoir levels in some flight-control electro-hydrostatic actuators (EHA) also caused concern, but the aircraft will return to flight with the existing EHAs.

The failure of an F135 engine during ground testing on August 30th remains the principle area of concern. Analysis indicated that the primary cause was a third-stage low-pressure blade failure that led to bearing and shaft failures

A safety assessment cleared the way for ground runs on AA-1 with flight-test engine number 1, with inspections between runs, and the engine has since run at full augmented power in the aircraft.

AA-1 eventually got airborne again at Fort Worth on December 7th 2007. After taking off at 1:20pm local time, test pilot Jon Beesley ran the engine at various power settings and checked the aircraft's flight characteristics at 6,000, 17,500 and 20,000 feet, and performed a fuel-dump test at 250 knots before returning to base at 2:15 pm. The F-35 will be flown at Fort Worth until about March 2008, when plans call for it to be flown to Edwards AFB for in-flight engine restart tests. When AA-1 returns to Fort Worth it will be used for flutter trials and for initial supersonic runs with the internal bay doors shut and open.

On its 26th flight on January 30th 2008 the F-35 was flown by a military pilot for the first time. Lt. Col. James "Flipper" Kromberg of the U.S. Air Force took off from Lockheed Martin's Fort Worth plant at 11:54 a.m. CST, flew the plane to 6,000 feet and checked handling qualities at 15-degrees angle of attack. He then climbed to 10,000 and 12,000 feet assessing the up-and-away flight-control response. Kromberg also tested the F-35's engine performance and formation-flying characteristics.

Lockheed Martin test pilot Jeff Knowles flew the F-35�s 27th flight later the same day.

On February 4th 2008 the F135 engine suffered a second turbine blade failure. The third-stage low-pressure turbine blade failed during proof testing of flight test engine (FTE) 6, the F135 scheduled to power the first STOVL F-35B, aircraft BF-1.

On February 19th 2008 BAE Systems completed critical fuel testing on the first F-35 Lightning II short take off and vertical landing (STOVL) variant five days ahead of its schedule. The testing continued 24 hours a day for 13 days, to check the calibration of the aircraft�s fuel gauging systems. Testing took place at Lockheed Martin�s Fort Worth plant.

On March 3rd 2008 Pratt and Whitney announced that the F135 engine had exceeded 9,000 system development and demonstration (SDD) ground test hours.

On March 12th 2008 the F-35A successfully completed the first stage of its airborne refueling tests during the aircraft�s 34th flight, which lasted for 1hr 34m. F-35 Chief Test Pilot Jon Beesley climbed to 20,000 feet and performed a series of maneuvers to verify the F-35�s compatibility with the KC-135's refueling boom and its aerodynamic wake. The sortie also evaluated aircraft systems and handling while connected to the refueling boom. All systems functioned as designed. Beesley reported that the F-35's flight control system provided excellent handling qualities near the tanker, and while connected to the tanker refueling boom.

The UK has made a significant change to its weapons fit plans for the F-35. The original intention was to clear four MBDA Advanced Short-Range Air-to-Air Missiles (ASRAAMs) for internal carriage but this has been revised to include two internal and two external weapons instead.

The external ASRAAM fit will be common across all three JSF variants and could therefore attract interest from other international customers, who will otherwise be tied to Raytheon's AIM-9X Sidewinder.

The new ASRAAM plan is a 'work swap' that does away with the requirement to clear the ASRAAM on the F-35's two internal air-to-ground weapon stations. The integration team now has the more straightforward task of providing underwing carriage on stations 1 and 11. The ASRAAM is a rail-launched missile and internal weapons must be carried on a trapeze that swings down clear of the F-35's weapon bay before they can be launched.

Carrying the ASRAAM outside the weapons bay brings several advantages, primarily in allowing passive beyond-visual-range (BVR) engagements cued by the missile's seeker or the F-35's infrared search and track sensor. But the downside is that it compromises the aircraft's very low observable (VLO) design.

On April 4th 2008 Pratt & Whitney announced that it completed all altitude testing necessary for flight qualification of the F135 short-takeoff/vertical-landing (STOVL) propulsion system at the U.S. Air Force Arnold Engineering Development Center in Tennessee.

On April 18th 2008 BAE Systems test pilot Graham Tomlinson throttled up the F-35B's engine to full military power in two consecutive tests. The F135 engine was evaluated for nearly an hour of run time at a variety of power settings. The engine runs were part of the F-35B�s first comprehensive systems checkout on the aircraft�s own power. The engine runs were preceded by successful tests of the Integrated Power Package, which combines the functions of a starter, generator, air conditioning and emergency power system.

The April 18th tests also included the opening and closing of all doors associated with the STOVL propulsion system. During STOVL flight, doors open above and below the shaft-driven lift fan and at the rear of the aircraft beneath the engine nozzle. A pair of auxiliary engine inlet doors opens behind the lift fan to feed more air to the engine.

On May 25th 2008 F-35B test pilot Graham Tomlinson performed two conversions from conventional (wing-borne) to STOVL mode with the aircraft anchored to a specially instrumented hover pit at Lockheed Martin�s STOVL Operations Test Facility at Fort Worth.

In early June 2008 the Dutch parliament approved participation in the initial operational test and evaluation (IOT&E) of the Joint Strike Fighter, and making a 10% down payment on two Lockheed Martin F-35As.

The second F-35 to fly, and the first STOVL version (F-35B), made its maiden flight on June 11th 2008. BAE Systems' test pilot Graham Tomlinson performed a conventional takeoff at 10:17 a.m. CDT from Fort Worth. Tomlinson took the jet to 15,000 feet and performed a series of handling tests, engine-power variations and subsystems checks before landing at 11:01 a.m. CDT.

Lockheed Martin plans to complete 20 flights with the first F-35B Joint Strike Fighter in conventional mode before replacing the engine to allow short take-off and landing (STOVL) tests to begin.

BF-1 is limited to CTOL flying until it is re-engined with a Pratt & Whitney F135 engine modified to eliminate a potential failure mode that caused the loss of single turbine blades in ground tests of two STOVL engines. The modified F135, flight test engine number 4, will be installed while aircraft BF-1 is on the ground later this year for a scheduled upgrade. Re-engining will allow BF-1 to begin STOVL testing in October 2008. This will involve running the STOVL propulsion system up to full power over the hover pit at Lockheed's plant in Fort Worth, Texas.

BF-1 is expected to return to flight in November, to begin CTOL-to-STOVL conversion tests by opening the doors in flight. Actual STOVL tests are scheduled to begin in the first quarter of 2009. This will involve 20 flights during which the aircraft will be flown progressively lower and slower until it completes a slow landing at Fort Worth. BF-1 will then relocate to the U.S. Navy's test center at Patuxent River for the first full vertical landings. These will be followed by short take-off tests.

On September 16th 2008 aircraft AA-1 flew with a full weapons load in its internal bays for the first time. The mock-up weapons duplicated the dimensions and weight of a typical F-35 strike mission load-out in full stealth configuration: two 2,000-pound Joint Direct Attack Munitions and two Advanced Medium Range Air-to-Air Missiles. With more than 5,000 pounds of ordnance in its internal weapons bays, performance remained strong, with no discernable indication of the degradation sometimes experienced in current fighters because of aerodynamic drag.

In preparation for its deployment to Edwards, the F-35A conducted a final series of in-flight refueling tests from its Fort Worth base, having taken on 12,000 pounds of fuel during a three-hour flight on September 25th.

Some time during this period AA-1 notched up its 50th development flight.

Meanwhile, aircraft BF-2 has undergone a range of handling-qualities tests, engine-power transitions from idle to full afterburner, extended its retractable fuel probe, and opened and closed all of the doors associated with its STOVL propulsion system. After 14 flights it began a planned modification interval that will lead to STOVL-mode flight in early 2009.

F-35A AA-1 arrived at Edwards AFB for the first time on October 1st 2008, having flown more than 1000 miles non-stop from Fort Worth NAS with test pilot Jeff Knowles at the controls. The aircraft refuelled in the air during the flight. During the F-35's deployment to Edwards, the flight test team will conduct ground and flight test activities for propulsion, aerial refueling and logistical support, and will hold training exercises for the test team.

On October 10th 2008 the Italian government confirmed that it was pulling out of the F-35 Initial Operational Test And Evaluation phase.

On October 23rd 2008 F-35 AA-1 finished all planned testing at Edwards AFB. During the three-week deployment to Edwards, most of the F-35's activity centered on a set of crucial tests that validated the aircraft's ability to shut down and restart its engine in flight. During the tests - conducted to ensure that the aircraft can regain power and be flown safely in the event of an engine flameout - the Pratt & Whitney F135 turbofan repeatedly restarted on command.

On November 13th 2008, on its 69th flight, F-35 AA-1 went supersonic for the first time, reaching Mach 1.05, or about 680 mph, 30000 feet above north Texas. The aircraft was carrying nearly 2.5 tonnes of inert weapons in its internal bays. The F-35 accomplished four transitions through the sound barrier, spending a total of eight minutes in supersonic flight.

Aircraft AG-1, the CTOL ground test airframe, was rolled out at Fort Worth on December 17th 2008. It will be fully instrumented before being shipped to BAE Systems/Brough in the UK for full-scale static testing in Q2 2009.

By December 19th 2008 aircraft AA-1 had completed 69 test flights, and BF-1 had completed 17 flights.

The first F-35B equipped with mission systems, aircraft BF-4, left the Lockheed Martin factory on January 21st 2009, and went to the fuel facility for functional fuel system checks before it is scheduled for delivery to the flight line by the end of January.

The aircraft will carry the Northrop Grumman AN/APG-81 AESA radar and Integrated Communications, Navigation and Identification suite, and the BAE Systems Electronic Warfare system. The Block 0.5 mission systems software, which incorporates more than half of the combat-ready Block 3 software, will drive the system.

On February 24th 2009 aircraft AA-1 successfully opened its weapon bay doors while airborne.

The second STOVL F-35B (BF-2) made its maiden flight at Fort Worth on February 25th 2009. During its flight BF-2 went through a series of maneuvers to assess its subsystems and basic handling qualities, and to check on-board instrumentation.

On March 19th 2009 Major Joseph T. "O.D." Bachmann became the first U.S. Marine Corps pilot to fly the F-35, logging the flight-test program's 90th mission with aircraft AA-1. He became the fifth pilot to fly the aircraft.

Bachmann departed the runway at Lockheed Martin's Fort Worth plant at 11:29 a.m. CDT and flew the aircraft to 15,000 feet, checking handling qualities and engine response before landing one hour and 15 minutes later.

During April 2009 the F135 engine in the first STOVL F-35B produced 41,100lb of vertical thrust during hover-pit testing. The requirement is 40550lb of thrust.

The aircraft was anchored to a metal grate 14 feet above a sloped concrete floor, separating the jet from ground effect and enabling it to simulate free-air flight. Sensors measured thrust and the aircraft�s response to pilot inputs. The testing also demonstrated control of the doors associated with the STOVL propulsion system: engine auxiliary inlet, fan inlet, fan exit, roll posts, and doors that open to enable the Rolls-Royce three-bearing swivel duct to articulate and vector engine thrust. In other tests, metal plates were installed on top of the hover-pit grate, enabling engineers to observe and chart the outflow of gases from the propulsion system.

The testing demonstrated functional operation of all systems required for vertical flight, and measured the installed forces and moments on the aircraft during STOVL operations. The hover-pit tests are the final series of ground tests before airborne STOVL testing begins.

On April 25th 2009 F-35 static test airframe AG-1 arrived at the BAE Systems facility at Brough after a 3-week voyage on a cargo ship from Houston. The airframe was transported with wings and canopy installed to the main fuselage, and was shrink-wrapped to provide protection against the elements. The resulting shipment was 51 feet long, 35 feet wide and 13.5 feet high, and weighed some 22 tons.

The F-35 airframe will be connected to a highly complex test rig in which 165 hydraulic actuators will replicate the loads the aircraft would see in flight. The data from the test will be captured by 4,000 sensors bonded to the airframe.

The test rig itself weighs around 365 tons and has approximately 53 miles of wiring spread around it to connect all the systems and sensors. Testing is planned to begin in late July and will take about 15 months, certifying the strength of the airframe and its components and contributing to the aircraft's flight envelope expansion requirements. Upon completion of its static testing program, AG-1 will be shipped back to the U.S.

The first flight of BF-01 in STOVL mode has been delayed, due to problems with the aircraft's engine. Also required are tweaks to the software controlling the leading edges, and to ensure that the nine doors that open during STOVL all operate correctly.

On June 23rd 2009 the F-35 flight test programme accomplished its 100th flight.

On June 16th 2009 the F-35 Highly Accurate Low Observable (HALO) pole model rolled out of Lockheed Martin's Fort Worth. The full-scale model will be a key component in validating the F-35?s Very Low Observable stealth performance.

On August 13th 2009 F-35B BF-2 became the first F-35 to complete an aerial refueling test using probe-and-drogue refueling system. This refuelling was the first of a series of tests in which fuel is uploaded into the aircraft at 10,000, 15,000 and 20,000 feet, at speeds ranging from 200 to 250 knots. The pilot on the initial F-35B aerial refueling flight was U.S. Marine Corps Maj. Joseph T. "O.D." Bachmann.

The refueling mission also marked the first time that a KC-130J tanker had been used to refuel an F-35. Previous refueling missions with the F-35A were accomplished with a KC-135 tanker.

According to Flight International on August 5th 2009, Lockheed Martin is developing a spoiler for F-35C Joint Strike Fighter flight test aircraft to counter potential wing drop in transonic turns. Wing drop in high rate transonic turns is a problem because it results in a turn becoming a roll. Because leading and t railing edge flaps may not be enough to counter this phenomenon, the carrier variant F-35C will have a 4.5kg (10lb) spoiler added to the centre of its outboard wing for the test programme.

F-35B BF-1 made its return to flight on September 4th 2009 with a 1-hour sortie from Fort Worth. The aircraft had been on the ground since September 22nd 2008 due to engine problems.

The first "optimised" CTOL F-35, aircraft AF-01, made its first flight on November 14th 2009. Lockheed Martin test piot David "Doc" Nelson lifted AF-1 off the runway at 13:34 local time and took the aircraft to an altitude of 20,000 feet and a speed of Mach 0.6. Nelson raised and lowered the landing gear, performed 360-degree rolls and lifted the nose to 20 degrees angle of attack during an 89-minute flight.

Meanwhile the first STOVL aircraft, BF-01, arrived at NAS Patuxent River on November 15th 2009, where it will begin vertical flight testing. Pilot Jon Beesley had left Fort Worth on November 12th, but had to wait two days at Dobbins AFB in Georgia waiting for the weather to clear.

Some problems came to light on BF-1 which delayed flight testing: a fuel shutoff valve needed replacing, which required the engine to be removed. At the same time the engine inlet rake was to be replaced, as it would run out of life before the 14-flight VL test program was complete. Also the canopy detonation cord (TRS) reached its expiration date on November 25th, so that was being replaced as well.

On December 29th 2009 the second F-35B (BF-2) arrived at NAS Patuxent River. USMC Maj. Joseph T. "O.D." Bachmann flew the aircraft nonstop from Fort Worth, Texas, completing one aerial refuelling during the 3h 19min flight.

On January 7th 2010 F-35B BF-1 engaged its STOVL propulsion system in flight for the first time. F-35 Lead STOVL Pilot Graham Tomlinson of BAE Systems took off from Patuxent River at 1:53 p.m. EST, climbed to 5,000 feet and engaged the shaft-driven LiftFan propulsion system at 210 knots, then slowed to 180 knots with the system engaged before accelerating to 210 knots and converting back to conventional-flight mode. The STOVL propulsion system was engaged for a total of 14 minutes during the flight. Tomlinson landed at 2:41 p.m. EST. STOVL-mode flights will continue, with the aircraft flying progressively slower, hovering, and ultimately landing vertically.

F-35 development dropped even further behind schedule in FY2009, according to a leaked report from the Director of Operational Test and Evaluation in January 2010. The two F-35Bs only conducted 16 out of a scheduled 168 sorties in FY2009. The delays could extend the development phase until mid-2016.

The report concedes that Lockheed has made progress in certain areas, particularly in structural testing. Load testing at up to 150% of the design limit has apparently gone smoothly, with only doors and a blade seal requiring redesign. The STOVL aircraft entered flight-testing with 64% of their allowable envelope cleared. The programme's goal is to clear 80% of the envelope in static testing by mid-2011.

On January 26th 2010 Royal Air Force Squadron Leader Steve Long became the first UK service pilot to fly an F-35, when he took F-35B BF-2 up on its 18th test flight at Pax River. Long took off at 09:55 EST and flew the aircraft to 20,000 feet, before landing 78 minutes later. He said that the aircraft performed "exactly like the simulators".

On January 27th 2010 lead F-35B test pilot Graham Tomlinson flew aircraft BF-1 down to 120kt in STOVL mode. This was the fourth flight from Pax River in which the propulsive-lift system was engaged.

BF-1 was slowed to 180kt with the lift-fan engaged on the first STOVL-mode flight on January 7th, then to 150kt on the second and third flights. The 48-min flight on January 27th was BF-1's 32nd and its fifth since arriving at Pax River on November 15th 2009.

On February 2nd 2010 the fifth F-35, a B model coded BF-03, made its maiden flight at Fort Worth, taking off at 16:02 local time. During the one-hour flight, F-35 Chief Test Pilot Jon Beesley tested the aircraft's handling, engine functions, landing gear and basic flight systems.

BF-3 was built and instrumented to conduct flight sciences test work and will be used primarily to evaluate vehicle systems and expand the aircraft's aerodynamic and structural-loads envelope. It will deploy later this year to NAS Patuxent River, where it will carry and release most of the weapons the F-35B will employ in combat.

Personnel from a private company called Wyle carried out the first refuelling of F-35B BF-2 using the probe-and-drogue system. The Wyle aircrew were flying a US Navy KC-130 tanker aircraft assigned to VX-20. This event appears to have happened before BF-2 arrived at Pax River at the end of December 2009.

On February 17th 2010 F-35B BF-3 took off from Fort Worth at 09:51 local time, and arrived at NAS Patuxent River three hours and 10 minutes later. Lockheed Martin F-35 Test Pilot Jeff Knowles was at the controls. BF-3 joins two other F-35Bs at the Navy test site, and will be used mainly to evaluate vehicle systems and expand the aircraft�s aerodynamic and structural-loads envelope. The airplane will also focus on weapons testing, and will carry and release most of the weapons the F-35B will use in combat.

On February 17th 2010 F-35B BF-1 made its first short landing at Pax River with the lift fan engaged and the jet exhaust deflected 90 degrees ().

As at March 1st 2010 the F-35 development flight counts were:

Aircraft FY07 FY08 FY09 FY10 Total
AA-1 19 36 35 1 91
BF-1 0 14 6 15 35
BF-2 0 0 10 12 22
BF-3 0 0 0 4 4
BF-3 0 0 0 3 3
Total 19 50 51 35 155

Given that 1243 test flights were planned for 2010, it is obvious that the F-35 development program is well behind schedule.

On March 10th 2010 test pilot Graham Tomlinson slowed F-35B BF-1 to 40 knots above NAS Patuxent River, before making a slow landing at 75 knots. The flight was one of the last missions before the aircraft's first vertical landing, and confirmed the jet's power and controllability at very low speeds. ().

On March 17th 2010 F-35B BF-1 completed its first actual hover. With its lift system engaged, the aircraft slowed from 150 kt to zero airspeed and hovered at 150ft for 2 minutes, moving up and down and left and right to check hover control. BF-1 then continued to to a short landing. Later in the day, BF-1 performed the first F-35 short takeoff. Matching performance predictions, the F-35B accelerated down the runway in STOVL mode and lifted off at 100 knots using less than 1000 feet of runway.

On March 18th 2010 BF-1 carried out the F-35B's first vertical landing. Lead STOVL Pilot Graham Tomlinson performed an 80-knot short takeoff from Patuxent River at 1:09 p.m. EDT. About 13 minutes into the flight, he positioned the aircraft 150 feet above the airfield, where he commanded the F-35 to hover for approximately one minute then descend to the runway. ().

It was reported on March 22nd 2010 that the third production-configuration F136 engine had successfully hit full afterburner at a GE test facility at Evendale, Ohio.

On March 27th 2010 the F-35C ground-test article (CG-1) was dropped 95 inches at 20 feet per second, with an 8.8-degree pitch, 2-degree roll, and 133-knot wheel speed, simulating a carrier-deck landing. During the testing, 500 sensors are monitored, with 2,500 points collected per second. The drop tests (of which 53 are planned) take place at Vought Aircraft in Dallas.

On April 7th 2010 the first mission system-equipped F-35B, BF-04, made its maiden flight at Fort Worth. During the flight, F-35 Test Pilot David Nelson climbed to 15,500 feet, verified engine response at varying throttle settings, performed a series of flight-qualities maneuvers and checked the operation of the aircraft's mission systems. The flight began at 10:04 a.m. CDT and concluded at 10:59 a.m.

BF-4 is scheduled to fly to NAS Patuxent River, where it will join three other F-35Bs currently undergoing flight testing. BF-4's general test objectives include providing data for mission systems software Block 0.5 functionality to evaluate hardware and software implementation and integration, and providing data to support mission systems component development.

Block 0.5 software incorporates important capabilities, including air-to-air search and synthetic aperture radar modes, identification friend/foe transponder, integrated UHF/VHF radios, electronic warfare radar warning receiver, and navigation functions. Information is presented to the pilot through state-of-the-art cockpit and helmet displays.

F-35A AF-2 made its maiden flight at Fort Worth on April 20th 2010. The jet, piloted by Lockheed Martin F-35 Test Pilot Jeff Knowles, took off at 17:57 local and flew for 1 hour. AF-2 will be used to verify the F-35A's ability to carry both internal and external weapons throughout the required flight envelope. The jet is also the first F-35 to have the internal GAU-22/A 25mm gun system installed. The system, featuring a four-barrel Gatling gun which fires at a rate of 3,000 rounds per minute, is made by General Dynamics Armament and Technical Products in Burlington, Vermont.

Gun testing on AF-2 will be used to confirm predictions of gun vibration, acoustic and recoil loads with the aircraft and various weapons. Additionally, the aircraft will be used to confirm vibro-acoustic loads with the weapons-bay doors open and closed with various weapon configurations. The measurements will validate the structural design of the jet, and provide evidence of the F-35A weapons' compatibility with gunfire and weapons-bay environments.

F-35As AF-1 and AF-2 arrived at Edwards AFB on May 17th 2010. USAF Test Pilot Lt. Col. Hank "Hog" Griffiths and Lockheed Martin F-35 Chief Test Pilot Jon Beesley flew the jets non-stop from Fort Worth. While the F-35s are at Edwards they will undergo ground- and flight-test activities for propulsion, aerial refueling, logistical support, weapons integration and flight-envelope expansion.

From May 1st to the 14th Lockheed personnel had completed 14 test flights, compared to 13 scheduled, and 74 for the year compared to 71 planned for the same time period.

The first F-35C, CF-01, made its maiden flight at Fort Worth on June 6th 2010. Lockheed Martin Test Pilot Jeff Knowles, a retired naval aviator and test pilot who flew F-14s operationally, and who served as chief test pilot on the F-117 stealth fighter program, took off at 11:46 local time and logged a 57 minute flight (see ).

The F-35C is unique in its uncompromised carrier suitability, with a larger wing and control surfaces for safe, precise handling and low approach speeds to the carrier, excellent over-the-nose visibility, and additional structural strength for at-sea operations. The aircraft's lo-observable materials are designed to withstand harsh carrier conditions with minimal maintenance.

F-35B BF-04, the first mission systems-equipped F-35, arrived at Patuxent River from Fort Worth on June 7th 2010. The aircraft was flown from Texas to Maryland by F-35 Test Pilot Dave "Doc" Nelson.

On June 9th 2010 Lockheed Martin announced that F-35A static load testing had been completed five months ahead of schedule, with no failures. The tests were carried out on airframe AG-1, largely at the BAE Systems' Structural & Dynamic Test Laboratory at Brough, and involved stressing the airframe to 150% of design limits, equivalent to a force of 13.5G.

On June 10th 2010 F-35B BF-2 became the first STOVL F-35 to go supersonic. On its 30th test flight US Marine Corps pilot Lt. Col. Matt Kelly climbed to 30,000 feet and accelerated to Mach 1.07 (727mph) in the off-shore supersonic test track near Naval Air Station Patuxent River. Future testing will gradually expand the flight envelope out to the aircraft's top speed of Mach 1.6.

F-35A AF-03, the second test aircraft with the next-generation avionics package, made its maiden flight at Fort Worth on July 6th 2010. Test Pilot Bill Gigliotti took off at 18:20 local and initiated a series of flying-qualities tests in a flight focused on propulsion and vehicle systems operation. Some mission systems data were collected before the 42-minute flight was curtailed by storms in the area.

AF-03 will begin testing with its AESA radar; electronic warfare system; integrated communication, navigation and identification system; inertial navigation system; global positioning system; integrated core processor; and helmet-mounted display system, then integrate other sensors as flight testing progresses.

On September 23rd 2010 Lockheed Martin test pilot Jeff Knowles completed the first open weapon bay flight tests on F-35A in a 90-minute mission from Edwards AFB. The mission included 360-degree rolls at 20,000 and 30,000 feet.

Also on September 23rd US Marine Corps pilot Lt. Col. Matt Kelly completed the fiftieth flight for F-35B BF-2. The 1.3-hour flight, from NAS Patuxent River, Maryland, involved performing accelerations and decelerations at 30,000 feet to test the air data system as well as performing flying quality test points and envelope expansion.

On October 1st 2010 flight testing of all F-35 Joint Strike Fighter variants was temporarily suspended until software that controls functioning of the engine's three fuel boost pumps had been modified. In addition, STOVL flight testing operations were prohibited for the F-35B variant after post-flight inspections revealed an issue on test aircraft BF-1.

The grounding order was lifted on October 5th after the installation of a software fix to prevent the BAE Systems-supplied fuel boost pump system from potentially failing in flight.

The cause of the F-35B's STOVL suspension was identified as a problem with a hinge on an auxiliary air inlet door immediately aft of the F-35B's lift fan. Lockheed Martin described it as a "durability issue involving a bearing-retention feature in the door's forward hinge".

By October 5th 2010 the nine aircraft in the test fleet had completed 270 flights. The bulk of them had been accumulated by the F-35A, with 115 flights completed. The F-35Bs have logged 141 flights, 40 fewer than scheduled. A further 124 flight tests are due to be flown by the end of the year.

On October 6th 2010 Lockheed Martin received a $13m contract from the UK MoD to incorporate a shipborne rolling vertical landing (SRVL) capability with the F-35B. The SRVL technique would enable the F-35B to return to an aircraft carrier's deck carrying more weapons or fuel than possible when making a vertical landing. This has been rendered academic following the UK's switch to the F-35C variant on October 19th 2010.

On October 18th 2010 RAF Sqn Ldr Steve Long took BF-2 to Mach 1.3 on the airplane's fifty-fifth flight. The test point was accomplished during a 1.5-hour flight from NAS Patuxent River. The flight also involved hot pit refueling, flutter testing, flying qualities, and performing other propulsion test points in conventional mode.

F-35A AF-2 completed the program's 300th flight of 2010 at Edwards AFB on October 20th. The two F-35As at Edwards Air Force Base are 61 flights ahead of plan, and the F-35C carrier variant is 5 flights ahead of plan, but the F-35B STOVL variant is 40 flights behind plan.

The status of some of the test aircraft as at October 21st 2010:

On October 25th 2010 F-35B BF-3 flew through 7g on its fifty-eighth test flight. The flight, from NAS Patuxent River, consisted of two sorties separated by hot pit refueling.

On November 5th 2010 F-35B BF-4 made the type's first flight with the Block 1.0 mission systems software. The functional check flight from Naval Air Station Patuxent River lasted 1.5 hours, and all planned test points were accomplished. The Block 1 software enables most of the primary sensors on the F-35, which possesses the most powerful and comprehensive mission systems package of any fighter ever to fly. Block 1 forms the foundation of all subsequent software blocks. It enables information fusion from the F-35's radar, electronic warfare system, distributed aperture system, electro-optical targeting system and other sensors, and provides initial weapons-release capability. The same software will be installed on the next two missions systems aircraft, AF-3 and CF-3, which are in final stages of production.

On November 6th 2010 F-35C CF-01 arrived at Naval Air Station Patuxent River to begin rigorous flight testing. The aircraft, piloted by David 'Doc' Nelson, departed Naval Air Station Fort Worth Joint Reserve Base at 11:31 local and arrived at Pax at 2:37 local. During the flight the aircraft conducted aerial refueling at a maximum load of 19,800lb.

Two and a half years after the first flight of an F-35B, on November 10th 2010 a formation flight was flown with two aircraft (BF-1 and BF-3). The flight was conducted at Naval Air Station Patuxent River at both 20,000 feet and 30,000 feet. It was the first to evaluate the close-proximity handling qualities of the F-35B.

On November 17th 2010 it was reported that the aft bulkhead of the F-35B BH-1 fatigue-test airframe had developed cracks after 1,500 hours of durability testing. This is less than one-tenth of the planned fatigue test program, which is designed to prove an 8,000-hour airframe life with a safety factor of two. The F-35B bulkhead design was modified in the course of the jet's weight-saving redesign in 2004-05, switching from forged titanium to a new aluminum forging process developed by Alcoa. The F-35A and F-35C variants still use titanium.

On November 18th 2010 the F-35 Lightning II program notched up its 500th flight when BF-4 took off from Naval Air Station Patuxent River on a three-hour test mission to evaluate avionics software.

On December 11th 2010 the third F-35A development aircraft (AF-03) arrived at Edwards AFB. Lockheed Martin test pilot Bill Gigliotti flew the aircraft on the 1,200-mile ferry flight from Fort Worth, refuelling from a KC-135 en route. AF-3 will focus on testing advanced technologies and mission systems. It is the second test plane, along with BF-4, to be equipped with the full suite of mission systems.

Lockheed reported that it had achieved its goal of 394 flights in 2010, and reached the 400-flight mark for the year-to-date on December 13th.

The fourth F-35A, AF-4, made its maiden flight at Fort Worth on December 30th 2010. This is the first F-35A with the full (current) mission systems on board. It was the 410th and final flight of the year, compared to 394 that were planned. But the F-35A is ahead of schedule, and the F-35B is behind.

F-35B BF-2 made its first vertical landing on January 6th 2010. On January 13th BF-2 made three flights, three sorties, 1.4 hrs time for 13 test points. Three short take-offs and three vertical landings were completed for three unique vertical landing test points including one with a 20 knot head wind.

F-35A AF-04 arrived at Edwards AFB on January 22nd 2011, after a 3.2-hour ferry flight from Fort Worth. The pilot was Maj. "Rip" Hayden.

F-35B BF-05 made its maiden flight at Fort Worth on January 26th 2011.

On February 4th 2011 Lt. Cmdr. Eric "Magic" Buus completed the first flight by a U.S. Navy test pilot in an F-35.

On February 26th 2011, F-35B BF-2 completed its 100th flight, with Lockheed Martin test pilot David "Doc" Nelson at the controls. On this flight BF-2 accomplished further short take-off envelope expansion test points in preparation for shipboard testing later in 2011.

The first (and so far only) F-35C broke the sound barrier for the first time on March 4th 2011. The aircraft reached Mach 1.02 at 30,000 feet with U.S. Marine Corps pilot Lt. Col. Matt Taylor at the controls during a test flight to expand the flutter envelope.

On March 7th 2011 F-35B BF-1 completed its 100th flight with BAE test pilot Peter Wilson at the controls.

On March 9th 2011 F-35A AF-4 experienced a dual generator failure and oil leak during flight operations at Edwards AFB. The aircraft landed safely, but flight testing was suspended while the cause of the generator failure was investigated.

Seven of the test aircraft had been cleared to fly again by March 16th, but AF-4, BF-5, CF-1 and production models AF-6 and AF-7 remained grounded. Airworthy aircraft are powered by an older version of the dual-redundant Hamilton Sundstrand electric starter-generators. The grounded aircraft are powered by an updated version of this equipment. As the F-35 relies on electricity instead of hydraulics to power flight-control surfaces, a dual-generator failure is a critical safety issue. By design, the F-35's electric system has a third back-up (Honeywell's integrated power pack) which kicked in and allowed the pilot of AF-4 to land safely.

The F-35B's main problems are:

  1. The auxiliary air inlet doors (which open as the aircraft is slowing down into a hover) proved too weak to handle the disruptive air flowing around the cover of the lift fan at a forward speed of 250 knots. The AAI doors are being completely redesigned.
  2. Bulkhead 496, which cracked only 10% of the way through a durability test, has to be strengthened.
  3. To land vertically without having to jettison stores or fuel, the F-35B either needs to reduce weight or increase thrust, or some combination of both.
These issues can be mitigated in the test aircraft, allowing them to fly all the test points needed for certification. But they need to be sorted before production can start.

The grounding of AF-4, BF-5, CF-1, AF-6 and AF-7 was lifted on March 28th. Flight clearance was reinstated after an investigation and test data indicated a maintenance procedure resulted in excess oil remaining within the alternate engine starter/generator (AES/G) lubrication system.

F-35B BF-04 made its first vertical landing at Pax River on April 27th 2011.

The second F-35C made its first flight from Fort Worth Joint Reserve Base on April 29th 2011. Lockheed Martin F-35 Test Pilot Bill Gigliotti piloted the jet on its first flight.

Up to May 11th, the F-35 fleet has conducted 331 flights in 2011. On May 6th a combined total of eight test flights were completed at the three flight test locations.

F-35A AF-6 (07-0744) was ferried to Edwards AFB on May 13th 2011. F-35C CF-2 was ferried to Patuxent River NAS on May 16th by Lt. Col. Matt Taylor.

The third F-35C development aircraft, CF-03, made its maiden flight at Fort Worth on May 21st 2011. The pilot was Dan Canin.

On May 21st 2011 F-35C CF-02 became the first F-35 to appear at an air show, when Lt Cdr Eric Buus made a single pass at the Andrews AFB Joint Service Open House. This was only the aircraft's seventh flight.

On June 3rd 2011 the third F-35C (CF-03) was flown from Fort Worth to to NAS Patuxent River by Lockheed Martin test pilot Dan "Dog" Canin. CF-03 will focus on mission systems, weapons integration, survivability and carrier suitability testing.

The Navy's F-35Cs were grounded on June 17th 2011 due to a software problem with the wing-fold mechanism that might have caused the flight control surfaces to freeze in flight. The grounding was lifted on June 23rd.

On June 25th 2011 F-35C CF-2 arrived at Joint Base McGuire-Dix-Lakehurst for jet blast deflector tests. On July 12th 2011 Naval Air Systems Command (Navair) reported that this testing was complete. It collected data on the effects of the F-35C engine exhaust on fleet-representative 4- and 6-panel blast deflectors and the flight deck in front of them, measuring temperatures, pressures, sound levels and velocities to collect environmental data and validate a model for cooling panel configurations on the deflectors.

On July 6th 2011 F-35A AF-2 completed the 1000th flight in the SDD test program.

On July 16th 2011 the fifth F-35B flight test aircraft arrived at Naval Air Station (NAS) Patuxent River. Lockheed Martin test pilot Bill Gigliotti flew the aircraft for the 3.5-hour flight from NAS Fort Worth Joint Reserve Base.

On July 19th 2011 F-35A AF-2 became the first F-35 to land on a wet runway at Edwards AFB, with Lockheed Martin test pilot Jeff Knowles at the controls. The 0.9-hour mission was AF-2's 135th flight.

As at July 26th 2011 the number of test flights carried out so far in 2011 was: F-35A : 250; F-35B : 187; F-35C : 81

On July 27th 2011 F-35C CF-3 made the type's first steam catapult launch at Lakehurst. Navy test pilot Lt. Christopher Tabert was at the controls for the launch.

All twenty F-35s were grounded on August 3rd 2011 after the Honeywell-built integrated power package (IPP) on AF-4 failed during a standard engine test following a maintenance check. Following the failure of the IPP (which combines the functions performed by an auxiliary power unit, emergency power system and environmental control system) the crew shut down the aircraft as per standard operating procedures.

On August 10th 2011 the F-35 Joint Program Office authorized a return to ground operations for the F-35 development aircraft. It appears that a control valve did not function properly on AF-4, and this led to the IPP failure. Monitoring of this valve is the mitigating action to allow ground operations.

The grounding was partially lifted on August 18th 2011, when development aircraft at Edwards AFB and Patuxent River were cleared to resume flight testing. The two production F-35As at Eglin AFB (AF-8 and -9) and Edwards (AF-6 and -7) remained grounded because they lack the monitoring systems used in the development aircraft that can detect problems in flight.

All F-35s were returned to flight status on August 25th 2011. Although the cause of the IPP failure on AF-4 is still under investigation, the F-35 JPO decided that with revised emergency procedures governing IPP failures in place, the aircraft can be flown safely.

On October 3rd 2011 Marine Corps test pilot Lt. Col. Fred Schenk made the first at-sea vertical landing for the F-35B, when he flew BF-2 onto the deck of USS Wasp off the mid-Atlantic coast at 15:12 local time.

The first vertical landing was part of the initial ship trials for the F-35B which were expected to last two weeks. The tests are scheduled to collect data on the aircraft's ability to perform short take-offs and vertical landings on a ship at sea, as well as determine how the aircraft integrates with the ship's landing systems, and deck and hangar operations.

F-35B BF-4 arrived on board USS Wasp on October 6th 2011. While Wasp was underway, the two F-35Bs logged more than 28 hours of flight time and completed 72 short take-offs and 72 vertical landings.

The trials ended on October 21st 2011. The next sea trial, DT-2, is scheduled for 2013 after Wasp receives additional modifications for F-35B operations.

 

During October 2011 the F-35 test fleet achieved 122 flights, with one aircraft, BF-2, completing 22 flights, the most ever for one aircraft in one month.

F-35A AF-1 reached the maximum design speed of Mach 1.6 for the first time on October 25th 2011.

As of November 3rd 2011 F-35C carrier variant jets had executed 59 successful catapult launches and three tail hook arrested landings in ground-based testing.

It was reported on November 18th 2011 that three of the five F-35B development aircraft had developed tiny cracks in a lift fan-related component which prevents them from reconfiguring in flight and landing vertically. BF-1 and BF-2 are being modified with a redesigned actuator support beam. BF-4 has also developed "hairline" cracks in the same part, but is continuing to fly in conventional mode only until the part is modified. BF-5 was built with the modified part, and no cracks have been found on BF-3. The impact on the test programme was thought to be minor.

A first launch of an F-35C using the Electro Magnetic Aircraft Launch System (EMALS) took place at Joint Base McGuire-Dix-Lakehurst, New Jersey, on November 18th 2011. Aircraft CF-3 performed a single launch from the General Atomics-built EMALS demonstrator system.

During 2011 the F-35 System Development and Demonstration flight test program called for the accumulation of 872 flights and 6,622 test points, but in fact 972 flights were flown and 7,823 test points were accumulated. The F-35A variant flew 474 flights and accomplished 3,600 test points. The F-35B variant accomplished 333 flights and 2,636 test points. The F-35C variant flew 165 flights and tallied 1,587 test points. Along with this, the F-35B executed 268 vertical landings. The cumulative 2011 milestones were achieved through a combination of planned test flights and test points along with test flights and test points added throughout the year.

On January 9th 2012 F-35A AF-4 reached the highest altitude to date in an F-35; 43,000 feet above Mean Sea Level.

The first night flight by an F-35 was carried out on January 18th 2012 by AF-6, which launched from Edwards at 5:05 p.m. PST and landed after sunset at 6:22 p.m. The mission consisted of a series of straight in approaches in twilight and darkness. Pilot Mark Ward also performed an evaluation of the F-35�s cockpit lighting.

On January 19th 2012 F-35B BF-7 was ferried to Eglin AFB.

On January 23rd 2012 the US SecDef announced that the probation on the F-35B had been lifted a year early.

On January 25th 2012 the F-35 SDD fleet (including AA-1, the original test aircraft) crossed the 2,500 flight hour threshold.

On January 30th 2012 all the F-35s at Edwards AFB and Eglin AFB were grounded because the parachutes in their Martin Baker US16E ejection seats were found to have been packed the wrong way round. The problem doesn't affect the seats in the F-35Bs and Cs at Patuxent River.

F-35A AF-1 was flying again on February 3rd after getting a new properly packed parachute head box assembly for its ejection seat.

On February 21st 2012 RAF Squadron Leader Jim Schofield became the United Kingdom's first military test pilot to fly the F-35C (aircraft CF-2).

On February 16th 2012 the first external weapons test mission was flown by F-35A AF-01 at Edwards Air Force Base. The weapons load for this mission was two AIM-9X Sidewinders on the outboard wing stations, two internal GBU-31 2,000lb laser-guided bombs and two AIM-120 AMRAAMs inside the two internal weapon bays. The aircraft also carried four empty external pylons that can each carry 2000lb of ordnance.

On February 22nd 2012 F-35B BF-02 flew with external weapons pylons for the first time. The test measured flying qualities with external pylons, inert AIM-9X Sidewinder air-to-air missiles and a centreline 25mm gun pod.

On April 21st 2012 F-35A AF-04 carried out the type's first aerial refuelling at Edwards AFB while carrying a weapons load. USAF Lt. Col. George Schwartz piloted the aircraft, which was carrying two external inert AIM-9X missiles and four wing pylons. Internally the jet was carrying two Joint Direct Attack Munitions and two AIM-120 AMRAAMs.

The first night launch of an F-35C took place on June 13th 2012. Marine Corps test pilot Lt. Col. Matt Taylor was aboard CF-2 for the flight.

On June 14th 2012 F-35B BF-2 completed the first test flight for the short takeoff and vertical landing variant with an asymmetric weapons load. Cmdr. Eric Buus flew BF-2 with an AIM-9X Sidewinder inert missile on the starboard pylon, a centerline 25 mm gun pod, and a GBU-32 and AIM-120 in the starboard weapon bay.

On August 8th 2012 F-35B BF-3, flown by Lockheed Martin test pilot Dan Levin, became the first F-35 to release a weapon in flight, when it dropped an inert 1000lb GBU-32 Joint Direct Attack Munition over an Atlantic test range while traveling at 400 knots at an altitude of 4,200 feet.

On August 9th 2012 BAE Systems announced that it had completed the static test programme on the AG-1 airframe and had returned it to Lockheed Martin at Fort Worth. During the tests the aircraft was 'flown' to its limits with loads applied to it replicating the effect of high gravitational forces well beyond any conditions likely to be met in actual flight. This was done with the airframe in a rig which was kitted out with over 4000 strain gauges, 170 actuators and over 50 miles of wiring.

Between August 8th and August 15th 2012 F-35B BF-2 successfully carried out a series of 27 air starts at various altitudes and using various methods at Edwards AFB. Air start testing is required for the F-35B to undertake high angle-of-attack trials in 2013. The F-35A has also completed air-start testing at Edwards.

On August 24th 2012 US Marine Corps Maj Joseph Bachmann, a test pilot assigned to VMFAT-501, flew Eglin's 200th sortie with the type.

On October 16th 2012 F-35A AF-1 completed the first in-flight weapons release of a 2000lb GBU-31 Joint Direct Attack Munition (JDAM) from an F-35A. The flight was conducted by U.S. Air Force Maj. Eric "Doc" Schultz. The aircraft released the inert, instrumented GBU-31 over the China Lake test range.

On October 19th 2012 F-35A AF-1 released an AIM-120 AMRAAM from an internal bay over the China Lake test range. The aircraft was flown by USAF Maj. Matthew Phillips.

During November 2012 F-35A AF-04 expanded its high angle of attack (AOA) test envelope to its 50 degree limit in only four flights at Edwards AFB.

On November 20th 2012 the final SDD F-35 (F-35C CF-5) made its maiden flight at Fort Worth. The aircraft was ferried to Patuxent River NAS by US Navy Lt. Cmdr. Michael Burks on December 12th. It will be used for ship suitability and high AOA tests.

On December 7th 2012 F-35B BF-01 made the 1000th flight of the B model. Marine Corps test pilot Maj. Russell Clift was at the controls for the flight at Patuxent River NAS.

On January 14th 2013 the DoD revealed that the specifications for all three variants pertaining to transonic acceleration and sustained turn rates were being reduced. The F-35C's turn performance will be reduced from 5.1 to 5.0 sustained Gs and time to accelerate from 0.8 Mach to 1.2 Mach by at least 43 seconds. The F-35A's time has slipped by eight seconds while the F-35B's time has slipped by 16 seconds. However, turn rates for both the A and B models have been impacted more severely. Sustained turning performance for the F-35B will be reduced from 5G to 4.5G while the F-35A drops from 5.3G to 4.6G.

On January 18th 2013 the F-35 Joint Program Office temporarily grounded the Lockheed Martin F-35B variant after the failure of a fueldraulic line in the aircraft's propulsion system. The incident occurred at Eglin AFB on January 16th while the mishap aircraft was undertaking a conventional mode takeoff roll. The pilot aborted the takeoff and the aircraft was secured.

On January 30th 2013 the JPO announced that the problem had been identified as a manufacturing defect in the fueldraulic line. Six other F-35Bs were found to have similarly defective fueldraulic lines. The grounding was lifted on February 12th. Aircraft will be returned to flight status when their fueldraulic lines have been inspected and replaced as necessary.

All F-35s were grounded on 22nd February 2013 due to a crack in a third-stage low-pressure turbine (LPT) blade in the F135 engine of F-35A AF-2 at Edwards AFB. The grounding was rescinded on 28th February after the crack was determined to have been caused to this particular engine due to "prolonged exposure to high levels of heat and other operational stressors".

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© David Hastings