AIR International’s Editor Mark Ayton and key.aero’s Editor Gary Parsons report on the F-35’s flight test programme.
The F-35A prototype, AA-1, above the desert during a test flight. This aircraft was retired in December 2009 after 91 sorties and was used as a live weapons target. All images Lockheed Martin unless credited otherwise.
When Lockheed Martin test pilot David ‘Doc’ Nelson climbed into his jet in the flight test barn at Fort Worth on November 14, 2009, his mission that day was significant – this was to be the maiden flight of the first optimised conventional take-off and landing (CTOL) F-35A Lightning II, AF-01.
Lockheed Martin uses the term ‘optimised’ to distinguish between the original prototype F-35A AA-01, which was built to the original design specification and gross weight, and subsequent aircraft that incorporate design changes made to reduce the aircraft’s weight. AF-01 incorporates parts that have been redesigned to provide additional strength or in other cases been made lighter as derived from the test programme of AA-01.
AA-1 first flew on December 15, 2006 in the hands of Chief Test Pilot John Beesley and was retired almost exactly three years later.Doc took off from Lockheed Martin’s plant at Naval Air Station (NAS) Fort Worth Joint Reserve Base at 13:34hrs local time. During the 89-minute test flight Doc flew to an altitude of 20,000ft (6,096m), achieved an airspeed of Mach 0.6, retracted and lowered the landing gear, performed 360° rolls and flew at 20° angle of attack. Commenting on the flight, Doug Pearson, Lockheed Martin Vice President for F-35 Test and Verification, said: “AF-01 is one of the most important aircraft in our test fleet because knowledge gained from its use expanding the flight envelope will benefit the other two variants – and every F-35 ever built.”
The first definitive F-35A, AF-01, first flew on November 13, 2009 enabling the original prototype AA-1 to be retired.The first flight of AF-01 is positive news for Lockheed Martin and its flight test team, but the aircraft should have taken to the air five months earlier. According to Lockheed Martin’s revised schedule of May 2008, 13 aircraft were to have flown by October 2009. In reality AF-01 is only the fourth F-35 aircraft to fly since the contract was awarded in late 2001. AF-01 has joined AA-01 (now grounded and undergoing destructive tests at Naval Air Weapons Station China Lake, California) and three F-35Bs, BF-01, BF-02 and BF-03 short take-off and vertical landing (STOVL) variants currently in flight test.
The first F-35B STOVL aircraft, BF-01, was the second aircraft to fly, becoming airborne on June 11, 2008.Jumping for joy
As Doc Nelson landed at 15:03hrs, his colleague Jon Beesley, Lockheed Martin’s F-35 Chief Test Pilot, was preparing for another notable flight that weekend. On November 15, Beesley flew F-35B BF-01 to NAS Patuxent River, Maryland, landing there at 12:46hrs local time. The move follows a series of hover pit trials at Lockheed Martin’s facility at Fort Worth. Patuxent River, known as ‘Pax River’, is the home of Naval Air Systems Command (NAVAIR) and the primary test site for the F-35B STOVL variant.
F-35B BF-01 made the first controlled vertical landing at Naval Air Station in Patuxent River, Maryland, USA on March 18, 2010. “Today’s vertical landing onto a 95ft square pad showed that we have the thrust and the control to manoeuvre accurately both in free air and in the descent through ground effect,” said F-35 Lead Short Take-off and Vertical Landing pilot, Graham Tomlinson, a retired Royal Air Force fighter pilot and a BAE Systems employee since 1986. Tomlinson positioned the aircraft 150ft above the airfield, where the F-35 remained in the hover for approximately one minute before descending to the pad. “The low workload in the cockpit contrasted sharply with legacy STOVL platforms,” he added, presumably referring to the Harrier and AV-8B.During the hover pit trials, BF-01 was anchored on top of a metal grid about 15ft (4.57m) off the floor of the pit, to enable the aircraft to simulate free-air flight and to measure the output of the propulsion system comprising the engine, variable nozzle, lift fan and vanes. BF-01 is now assigned to the F-35 division of Air Test and Evaluation Squadron 23 (VX-23) ‘Salty Dogs’, one of NAVAIR’s resident units at Pax River and part of the F-35 Integrated Test Team.
Initially test pilots will complete shorter take-off runs and slow the aircraft down during landing so that lift from the wing can be transitioned to the aircraft. This transition phase is critical before an actual vertical landing. Trials will also involve flight deck operations using a purpose-built ramp to replicate a ‘ski-jump’ equipped aircraft carrier, and further testing will include flying with different weight loads, ordnance payloads, and work-ups to shipboard operations.
The vertical landing flaps and doors of the STOVL F-35B are clearly illustrated in this image of BF-01 during flight testing.Commenting on the arrival of BF-01 at Pax River, Lt General George Trautman III, US Marine Corps Deputy Commandant for Aviation, emphasised the need to make up the delays in flight-testing of the F-35. “I’m anxious to have our engineers, our test pilots, and our operators get their hands on this jet, and then see what we can do to turn test points and sorties at a rapid rate during the coming months.”
BF-01 is the first of five F-35Bs due to be assigned to Pax River and is the first Lightning II to be sustained by the F-35 Autonomic Logistics Information System (ALIS). It will be monitored by the Lockheed Martin F-35 Sustainment Operations Centre at Fort Worth – ALIS will be used to support the worldwide fleet as soon as the type enters service.
BF-02, the second F-35B, flew in February 2009 and was the first to be piloted by a pilot from the Royal Air Force.Two follow-on aircraft, BF-02 and BF-03, were delivered in January and February respectively, with the first mission systems-equipped F-35B, BF-04, arriving in April. BF-03 is being used to evaluate vehicle systems and expand the aircraft’s aerodynamic and structural-loads envelope as well as weapons testing, while BF-04 is equipped with an avionics suite more representative of the final production version, incorporating the Northrop Grumman AN/APG-81 Active Electronically Scanned Array (AESA) radar; the Lockheed Martin Electro-Optical Targeting System (EOTS); the Northrop Grumman Electro-Optical Distributed Aperture System (EO-DAS); a BAE Systems Electronic Warfare (EW) system; a VSI Helmet Mounted Display System (HMDS); the Northrop Grumman Integrated Communication, Navigation & Identification (ICNI) friend-or-foe identification; the Lockheed Martin Integrated Core Processor (ICP) with Block 0.5 functionality; a Honeywell Inertial Navigation System and Raytheon Global Positioning System. The new avionics package has already undergone more than 100,000 hours of laboratory testing and flight testing in the Cooperative Avionics Test Bed (CATB), a highly-modified Boeing 737 incorporating an F-35 cockpit layout.
The third STOVL aircraft, BF-03, flew on February 4, 2010 as the testing for the US Marine Corps version pushes forward.Production progress
During AIR International’s visit to Fort Worth in late 2009, there were 31 Low Rate Initial Production (LRIP) aircraft in various stages of assembly, including all 12 aircraft from LRIP 2. Five aircraft were in mate stations on the final assembly mating line: the US Navy’s first F-35C carrier variant CF-01, one F-35B (BF-05) and three F-35As; AF-03 and aircraft from LRIP 1 that are destined for the training unit at Eglin Air Force Base in Florida. CF-01 was back on the line despite the July 28, 2009 ‘roll-out’ As the first of its kind, the aircraft was due to go out to the fuel barn in January to undergo fuel system calibration work. Lockheed Martin hopes to undertake its maiden flight in the first half of 2010, but had not done so by the time this article went to press.
The first F-35C, CF-01, is rolled out for the US Navy in August 2009.Lockheed Martin is banking on its continuously moving mating line to move at 50 inches (1.27m) per hour at rate production. When AIR International visited the line it was static, but would soon move at 4 inches (100mm) per hour, according to one company employee.
Test vehicle CG-01 is being used by sub-contractor Vought to measure simulated carrier landings by being dropped from various heights. Vought imageFull-scale drop tests
In mid-November Vought Aircraft Industries in Dallas, Texas, took delivery of F-35C carrier variant CG-01 from Lockheed Martin to perform full-scale drop testing. Test objectives include structural verification of the landing gear and airframe in accordance with US Navy requirements for carrier landing operations. CG-01 is fitted with special drop test fixtures, test systems and instrumentation to measure loads, stresses, deflections and accelerations at various locations on the landing gear and airframe.
The tests were successfully carried out between March and April, and included dropping CG-01 95 inches at 20 feet per second, with an 8.8 degree pitch, two degree roll, and 133 knot wheel speed, simulating a carrier-deck landing. Nearly 500 sensors were monitored, with 2,500 points collected per second.
An F-35 cockpit has been fully flight tested in this Boeing 737 test aircraft owned by Lockheed Martin.Types of aircraft
To some eyes, each F-35 aircraft rolling off the Fort Worth production line looks much the same, but there are in fact three types of aircraft. First there are those used as static and durability test articles, and then two kinds that fly: flight science aircraft and mission system aircraft. Lockheed Martin built six ground-based test articles; one static and one fatigue of each A, B and C variant.
Flight science aircraft carry instrumentation for measuring parameters such as structural loads and are used for expanding the flight envelope. Mission system aircraft are fitted with Communications, Navigation and Identification (CNI), Defensive Aids Systems (DAS), Electro-optical Targeting System (EOTS), Electronic Warfare (EW) packages and the APG-81 Active Electronically Scanned Array (AESA) radar and carry instrumentation to measure systems performance parameters such as temperature and vibrations.
The X-35 prototype that won the fly-off competition against Boeing’s X-32.Out of shape?
As this gargantuan programme moves slowly forward, Lockheed Martin remains behind schedule and over budget. So much in fact, that the latest Pentagon appraisal of the programme cites that two more years and billions of additional dollars are required to complete the F-35’s development.
To preserve its stealth capabilities, the F-35 has been designed with internal weapons bays.In January a report issued by the US Defense, Operational Test and Evaluation Directorate (DOT&E) poured more fuel on the fire of concern over slipping deadlines and development timescales. The DOT&E reports directly to the US Defense Secretary, Robert Gates and is responsible for reviewing and analysing the results of OT&E for each major Department of Defense (DoD) acquisition programme. Dr Michael Gilmore, the Director DOT&E said that “the verification and flight test [programme] did not reach the tempo planned for FY09 due primarily to late deliveries of the remaining ten (of 13) System Design Demonstration (SDD) flight test aircraft.” He added that only 16 of a planned 168 flight test sorties had been accomplished.
According to Dr Gilmore, the deployment plans of the DoD for the F-35 are at “substantial risk” given the current pace of the programme and that completion of initial OT&E capability could only occur in early to mid-2016 provided the associated extension of SDD is supported with “additional flight test aircraft, timely delivery of effective software, and an adequate pace of testing is maintained.” Dr Gilmore is also critical of the clarity of what constitutes initial operational capability, stating that the mission capability of the low-rate initial production (LRIP) aircraft and support systems is “unclear.”
BF-01 is shadowed by an F/A-18 chase aircraft on a sortie from NAS Patuxent River in Maryland where the majority of the F-35 programme is being conducted.The ‘weight loss’ programme of recent years has also brought increased risk, he said, as “recent removal of shut-off fuses for engine ‘fueldraulics’ lines, coupled with the prior removal of dry bay fire extinguishers, has increased the likelihood of aircraft combat losses from ballistic threat induced fires.”
This was followed in March by a report from the US Government Accountability Office (GAO), saying that a “new, comprehensive, and independent assessment of the costs and schedule” should be made by the Department of Defense (DoD) before committing to production decisions.
The report, entitled ‘Additional Costs and Delays Risk Not Meeting Warfighter Requirements on Time’ said that the total estimated costs had increased by $46 billion and the development timeline extended by two years over that agreed just three years before. Total cost of the programme was then estimated at $323 billion through to 2035, it being the DoD’s “most costly and longest acquisition programme.” Life-cycle costs for operating, sustaining, and maintaining JSF fleets were estimated at $764 billion, substantially higher than earlier estimates and also more than legacy aircraft the type will replace, said the GAO.
It also criticised the pace of the flight test schedule, saying manufacturing the test aircraft “continues to take more time, money, and effort than budgeted.” In summary the GAO recommended that together with a review of costs, likely to be forced through a breach of the ‘Nunn-McCurdy’ rule within Congress, that the dates for achieving initial operational capabilities (IOC) must be delayed or the military services “will have to accept less initial capability” and defer desired requirements to future upgrade programmes. It particularly pointed to the US Marine Corps’ stated intent to achieve IOC in 2012 when production aircraft are unlikely to be delivered until 2013. As an indication of the USMC’s resolve, the first active-duty F-35 squadron formally stood-up as the US Marine Corps (USMC) F-35B Lightning II training squadron, Marine Fighter Attack Training Squadron 501 (VMFAT 501) on April 2.
Squadron Leader Steve Long, a Royal Air Force serviceman became the first active-duty pilot from the UK to take the controls of the F-35B Lightning II Joint Strike Fighter in January 2010. Sqn Ldr Long flew BF-02 on a sortie from Naval Air Station Patuxent River on its 18th test flight, taking the aircraft to 20,000ft on the 80 minute flight. "Flying the F-35 was exactly like the simulators that I've been flying for over 18 months,” he said. He is currently on an exchange programme with the US Marine Corps flying the F/A-18C. British pilots and ground crew will soon start initial training at Eglin Air Force Base in Texas in readiness to receive the first production aircraft.VFMAT 501 ‘Warlords’ is embedded in an Air Force wing, being part of the 33rd Fighter Wing based at Eglin Air Force Base in Florida, a first for a USMC squadron. The unit was redesignated from VMFAT 451, a 13-year retired squadron that was reactivated on April 1. The squadron is hoping to receive its first F-35B before the end of the year, depending upon Lockheed Martin’s development programme, and the USMC still hopes to have eight initial cadre and two operational test pilots trained by the end of 2011.
The US Navy’s F-35C variant was also facing a redesign, said the report, as “significant design modifications to the keel web, a key structural joint to enable catapult take-offs” was required.
With its recommendations for F-35, the GAO said that contingency plans for ‘legacy’ aircraft (such as F/A-18C) needed to be developed so that a properly resourced strategy is in place to fill capability and capacity gaps until the F-35 achieves IOC in the respective services.
On March 25 the Pentagon officially notified US Congress of the F-35 programme’s breach of cost limits under the ‘Nunn-McCurdy’ legislation, requiring a complete review of the whole programme.
F-35 slides up to a KC-135R during a test sortie.The Nunn–McCurdy Amendment or Nunn–McCurdy Provision was introduced into US legislation in 1982 by Senator Sam Nunn and Congressman Dave McCurdy and is designed to curtail cost growth in weapons procurement programmes. The amendment requires programmes with cost escalations of more than 25% to be cancelled unless the Secretary of Defense can prove it is essential to national security and that no viable option is available. There is little likelihood of F-35 being cancelled, as Secretary of Defense Robert Gates will undoubtedly argue there is no alternative to the multi-billion dollar fighter. What is likely is that procurement plans will be reviewed with fewer fighters bought for the US forces and a possible rationalisation of the versions planned, with the F-35B and F-35C both experiencing technical difficulties. This is the second time that the F-35 faces a Nunn-McCurdy breach – the first was in 2005 when the project was re-baselined after several redesigns forced through the ‘weight-loss’ programme.
Engines – one or two?
One of two engines currently being developed for the F-35, Pratt & Whitney’s F135 undergoes a full-power static test.A constant debate in Congress is whether two different engines should be funded for the F-35 – the Pratt & Whitney-led F135 and the General Electric-led F136. In US President Obama’s budget statement in March, the battle lines were once again drawn.
With Congress having battled successfully to keep the General Electric and Rolls-Royce F136 Alternative Engine Program (AEP) alive in the 2010 Defense Appropriations Bill, Obama’s defence budget proposals for 2011 will once again try to kill the F136 through “prioritising resources by ending or reducing several programmes, including the C-17 aircraft and the Joint Strike Fighter Alternate Engine.”
The AEP has been a political battleground for the last few years, and the Obama Administration says “the reasons for cancelling the AEP in 2007 remain valid today.” It believes a second engine “is unnecessary - financial benefits, such as savings from competition, have been assessed to be small, if they exist at all”.
The second F-35A, AF-02, was the latest aircraft to join the test fleet on April 21, 2010.A complex process
Considering the magnitude of the task, cost overruns are perhaps unsurprising. Concurrent development of three different variants of the most complex fighter aircraft, set to be built on a continuous moving production line at one plant, supplied by subcontractors based around the world, is not a simple task.
Lockheed Martin provided statistics to show the scope of the system design and development task of the F-35. Two in particular show the kinds of numbers involved in F-35: to date, 48,704 build to package (BTP) line items have been finished, and 55% of the projected changes required to BTPs as part of the redesign are complete. And what about software? Everything that functions on the jet is controlled by computer, for which there are 18.8 million lines of code, 78% of which has been tested and released.
With an estimated total cost in excess of $300 billion for thousands of aircraft supplied to multiple air arms around the world, the entire F-35 programme is by any stretch of the imagination ambitious. The current problems appear to match that ambition. Lockheed Martin’s goal is to build one F-35 every day. If it and its programme partners reach that milestone, future visits to the Fort Worth production line will be a sight worth seeing.
Filed Under Military Aviation Features.
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