The world's biggest military aircraft programme is ending 2010 in much the same manner that it started the year, with uncertainty surrounding its long-term health, cost and delivery schedule.

But in reality, it has been a fair past 12 months for Lockheed Martin's F-35 Joint Strike Fighter, with the company's test fleet on track to meet its revised flight test goals and its "programme of record" for just over 3,100 aircraft still intact - for now at least.

The programme in March achieved the first vertical landing by an F-35B, and another major boost came in July, when Canada formally selected the conventional take-off and landing F-35A to meet its requirement for at least 65 new fighters.

 F-35 assembly, ©Lockheed Martin
More than 200 F-35s should be assembled in Fort Worth per year at peak rate. Picture: Lockheed Martin
More aircraft have joined the flight test fleets at Edwards AFB in California and NAS Patuxent River in Maryland, with eight of an eventual 12 airframes now delivered. In mid-November, Lockheed also celebrated the 500th flight since the type's debut in December 2006. The company expects to beat a target to fly 394 sorties this calendar year, with its total likely to be around the 400 mark.

On the international stage, an agreement has been reached with Israel, which looks set to become the first Foreign Military Sales customer for the fifth-generation type, with a planned initial purchase of 19 or 20 aircraft. However, company officials believe the nation could eventually acquire around 75 over the life of the programme.

But setbacks have not been in short supply, with interruptions experienced during testing of the programme's most challenging variant, the STOVL F-35B. These have been caused by unexpected wear on door hinges for its Rolls-Royce Liftfan propulsion system. And although around 85% of the programme's required software has now been written, the remaining portion is the most difficult, as it concerns data fusion.

F-35, ©Lockheed Martin
The US Air Force plans to acquire 1,763 conventional take-off and landing F-35As. Picture: Lockheed Martin
In mid-October, the UK government surprised many - including Lockheed's senior programme officials - by switching its planned production allegiance from the F-35B to the larger C-model carrier variant (CV). However, it remains notionally wedded to buying up to 138 of the type, although firm details about its eventual fleet requirements will emerge only during its next Strategic Defence and Security Review in 2015. The UK's switch leaves the F-35B with commitments from only the US Marine Corps and Italy's navy and potentially air force also.

Separately, the results of a recent baseline technical review into the JSF programme's overall health are likely to be disclosed soon. Some forecasts suggest that this could result in a further cost overrun of up to $5 billion and a new schedule slip of around one-year. This has fuelled recommendations from some quarters - including a presidential commission - that the US Department of Defense should cancel its minority variant, the F-35B, or even terminate the programme altogether.

Lockheed declines to comment on such speculation, but its executive vice-president F-35 programmes Tom Burbage believes that current issues facing the company are close to being resolved. "We have some challenges, but they're not of the same magnitude that we've seen on other programmes," he says. Other officials stress that the USMC remains committed to future operations with the STOVL aircraft.

Production activities are meanwhile ramping up on Lockheed's mile-long final assembly line in Fort Worth, Texas. In addition to early examples for the US Air Force, US Navy and USMC, the first test aircraft for international customers are now in work. The Netherlands and the UK will receive one and two aircraft each from the programme's third low-rate initial production (LRIP-3) batch to support initial operational test and evaluation (IOT&E) activities.

Planned F-35 order book

David Scott, the company's director F-35 international customer engagement, says the Netherlands should make a decision within the coming months on whether to approve a second F-35A under the recently-signed LRIP-4 deal, which so far totals 31 aircraft. These include the UK's third STOVL jet, although the latter has asked whether it can swap this for an F-35C instead.

So far, 62 LRIP aircraft have been ordered, on top of the 19 already-produced flight and ground-test examples funded during the programme's system development and demonstration phase.

Lockheed had by early December delivered the two aircraft from LRIP-1 and one from LRIP-2 for flight test. Nine more from the second batch are now in final assembly and another two in mate, with these accompanied by the first five of 17 LRIP-3 assets.

Australia should sign for its first 14 of a planned 100 F-35As during 2011, and by mid-2012 all the programme partner nations bar Denmark should have placed their first production orders.

Copenhagen recently announced a two-year deferral to a decision on replacing its F-16 fighters, and could also reduce its planned acquisition from 48 to 30 aircraft.

Lockheed also now cites Belgium, Finland, Greece, Japan, Singapore, South Korea and Spain as possible near-term FMS customers. "We have a potential market over the next 15 years for anyone using the F-16," says Scott. Burbage is more bullish, claiming: "The further out in time you go, the more F-35 becomes the dominant fighter."

The assembly rate will be increased to a peak of 20-22 aircraft per month within around six years. This compares with a current output of around 22-24 F-16s per year, with the type still in production for customers including Egypt, Morocco and Pakistan. Lockheed officials note that the legacy type started out with a planned production run of just over 1,000, but that more than 4,500 examples have now been sold.

Currently using fixed stations on a pulse line, the Fort Worth facility will later be transitioned to a moving model, with this borrowing on the techniques employed in the motor industry. The F-35's four main assemblies - forward, centre and aft fuselage and wing - will be mated together on the common line, all with the same engines and avionics equipment. The use of so-called "cousin" components will be required between the types, for example to strengthen the F-35C for carrier operations and to enable the CTOL variant to meet the USAF's mandated requirement to perform manoeuvres at up to 9g. This compares with 7.0g and 7.5g respectively for the programme's B and C variants.

A final assembly and check-out line for the F-35 is also to be established at Cameri air base in Italy, with a capacity to complete between two and three aircraft per month and also provide in-service support for the nation and possibly other European operators also.

Responding to criticism over the planned placement of manufacturing contracts with Israeli firms, such as for the second-source production of wings by Israel Aerospace Industries, Burbage says the arrangement is based on a best-value judgement. The work will also be drawn from Lockheed's own workshare, and not affect an existing relationship with Alenia Aeronautica.

"Our commitment to the partners was that none of the work that was identified for the partner industries would be offered to the Foreign Military Sales [customers]," says Burbage. "We've honoured that commitment." He also notes that the programme's international partners all stand to benefit from FMS sales, due to reduced unit costs and rebates linked to their financial investments in the F-35's development.

Ottawa's selection of the F-35A also proves to be a continuing source of controversy for the Canadian opposition and media, with questions raised over the apparent lack of a competition.

"We've been making the arguments that I don't think need to be made," says Burbage. "Canada was the first country to join after the contract was awarded - in February 2002 - and there really is nothing else to compete against." Lockheed believes that the nation could in time buy up to 80 aircraft to meet its long-term requirements.

Meanwhile, lessons are already being learned from today's limited use of the JSF, with an operations centre at Fort Worth supporting test activities at the site and at Edwards AFB and Patuxent River. "We're not waiting for IOT&E, we're collecting data in test and learning as we go." says Kimberly Parker Gavaletz, Lockheed's vice-president F-35 autonomic logistics global sustainment. "That really brings the cost down."

F-35, ©Lockheed Martin
The programme's carrier variant is strengthened to survive embarked operations. Picture: Lockheed Martin
All operators will be able to access aggregated technical data about the type once it has entered frontline service, while the use of a common asset management system will also allow them to draw from a spare parts pool, while also having the ability to fence off some key equipment.

Lockheed officials decline to reveal the possible number of F-35 test flights to be achieved during 2011, but confirm that the type will fly for the first time late in the year with the programme's alternate engine. While the long-term fate of the General Electric/Rolls-Royce F136 remains in the hands of US lawmakers, the design has survived several previous termination attempts.

And despite the strong international interest in potential FMS orders for the F-35, the manufacturer says the type will not be making it debut appearance at an air show within the next 12 months, with all efforts to be placed on keeping flight test activities on track.

Despite the challenges facing the programme, Burbage is optimistic that the F-35 will deliver on Lockheed's promise to the type's future operators - and in all three variants. "I think that when you look across the partnership everybody has good faith that the US is going to deliver the airplane that people need, and confidence in the process that we've used to develop it," he says. "On balance, we're pretty pleased with where we are moving forward."

Lockheed Martin was surprised by the UK's mid-October decision to switch its planned production order for the Joint Strike Fighter from the short take-off and vertical landing F-35B to the carrier variant (CV).

A result of the Strategic Defence and Security Review, the shift will see the Royal Air Force and Royal Navy Fleet Air Arm operate an aircraft which Prime Minister David Cameron says is "more capable, less expensive, has a longer range and carries more weapons". It will also boost interoperability with the French and US navies, he adds.

"We knew it was an option being looked at, but I would categorise it as having been somewhat unexpected," says Lockheed executive vice-president F-35 programmes Tom Burbage of the variant switch. The manufacturer is now trying to assist the UK as it bids to change an order for a third test STOVL aircraft to the F-35C.

Such a change of direction would have been impossible on a smaller programme, but Burbage says: "You can make decisions like this, and you can accommodate them."

Key differences between the CV and STOVL aircraft are in their wing spans - 13.1m (43ft) and 10.7m, respectively, and wing areas: 668ft2 (62m2) and 460ft2. This will enable the larger aircraft to land on an aircraft carrier's deck at a speed of around 145kt (268km/h). The F-35C also has a strengthened landing gear, tailhook and wing-fold to support embarked operations, and can carry 1,360kg (3,000lb) more in internal weapons. Its range using only internal fuel is greater than 2,220km (1,200nm).

F-35, ©Lockheed Martin
Three STOVL-variant test aircraft are already on order for the UK. Picture: Lockheed Martin

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Source: Flight International