JANE'S DEFENCE WEEKLY - SEPTEMBER 22, 2004
Answers found to F-35 weight problem
MICHAEL SIRAK JDW Staff Reporter
Washington, DC
The US head of the multinational F-35 Joint Strike Fighter (JSF) programme said he is "cautiously optimistic" that engineers have identified ways to shed weight in the aircraft's design so that it will meet, if not exceed, all its performance requirements.
"We feel our proposed configuration is operationally viable," US Navy Rear Adm Steven Enewold, the F-35's programme executive officer, said on 14 September. The next step, he said, is for the senior acquisition oversight panel within the US Department of Defense (DoD) to review, and hopefully approve, the changes during a meeting scheduled for mid-October.
He did acknowledge, however, that an independent review team brought in to examine the programme regarded the weight as a "bigger" issue than the programme office sees it, although the team was complimentary about the aircraft's design.
Warning bells sounded within the programme late in 2003 when it emerged that the projected weight of the F-35B short take-off and vertical landing (STOVL) variant might hamper its ability to perform short take-offs and return to ship and land vertically when carrying ordnance and reserve fuel. The DoD slowed the pace of the JSF programme as a result so engineers could go back and study ways to improve the design.
Adm Enewold said they have identified changes that would remove 2,700 lb (1,224kg) from the aircraft and, together with proposals for improving propulsion efficiency, reducing drag and tweaking the way the aircraft is operated, would enable it to perform to specifications. These improvements would also cascade into the F-35A conventional take-off and landing (CTOL) variant and the F-35C navy carrier (CV) version, the designs of which have not had the same weight issues.
Tom Burbage, Lockheed Martin's JSF executive vice president and general manager of programme integration, said the design changes include improving engine inlet efficiencies and exit flows; reconfiguring how centre fuselage sections are mated; realigning wing spars more closely to allow for thinner wing skin; using a double door with the nose landing gear to reduce cross-wind effects and allow for a smaller vertical tail; creating a full-depth bulkhead in the weapons bay; using smaller sized batteries; and expanding the outer mould line of the aircraft to accommodate more fuel.
Engineers have also reverted to the original, smaller internal weapons bay design for the STOVL aircraft. It can accommodate two AIM-120 Advanced Medium-Range Air-to-Air Missiles (AMRAAMs) and two 1,000 Joint Direct Attack Munitions (JDAMs) as opposed to the larger bay resident in the CTOL and CV models that holds two AMRAAMs and two 2,000 lb JDAMs. Programme officials had planned for a time to use the larger bay in the STOVL model.
While the programme office awaits the DoD's approval for the changes, the air force is mulling STOVL design alterations of its own, like an internal gun and boom refuelling capability, as it considers what it wants in this variant. In February the service announced its intention to buy the STOVL jet as well as the CTOL version.
Gen Hal Hornburg, commander of Air Combat Command, said on 14 September the service would like to have both capabilities in the aircraft, but has been told it may face an 'either-or' situation. The STOVL design currently can carry only an external pod-mounted gun and is configured for hose and drogue refuelling.
Burbage and Adm Enewold said they are examining what would need to be done to accommodate the air force's wishes. Burbage told JDW that the service has indicated to him a keener interest in the internal gun. Fitting it would require reducing the aircraft's fuel capacity by about 700 lb, he said. Adding both the gun and boom receptacle would be "difficult", he noted.
Air Force Chief of Staff Gen John Jumper said the air force will probably buy the F-35B "in the hundreds" to populate dedicated close-air-support squadrons to support the US Army and US Marine Corps.
Lockheed Martin, along with industry partners BAE Systems and Northrop Grumman, is building the first test aircraft: a CTOL unit. The first flight is anticipated around August 2006.
Current unit cost estimates are $45 million for the CTOL model and $55 million to $60 million for the CV and STOVL variants, said Adm Enewold.
JANE'S DEFENCE WEEKLY - OCTOBER 13, 2004
JOINT STRIKE FIGHTER - Happily ever after?
Robert Hewson Editor Jane's Air-Launched Weapons
As Lockheed Martin's Joint Strike Fighter approaches production, questions still surround the programme, not least for the UK. Robert Hewson examines recent developments and problems on the horizon
The news from Fort Worth is that the design difficulties and performance worries that have been irritating Lockheed Martin's F-35 Joint Strike Fighter (JSF) partners have been solved, and official hopes for an October production clearance from the US Department of Defense are high.
Lockheed Martin wants to turn its attention towards JSF production, with work on major aircraft assemblies now well under way in the US and the UK. The first flight date for the first F-35 is set for August 2006 and, after a troublesome 12 months spent grappling with key design issues, the JSF would appear to be facing a brighter future. However, the dust from the crucial weight reduction work has yet to settle. In producing a design that now meets its desired Key Performance Parameters, Lockheed Martin has made some significant changes to the troubled F-35B Short Take-Off Vertical Landing (STOVL) variant that may yet fail to deliver everything its customers expect.
At the same time, the greatest JSF customer expectation of all - that of equal partnerships with meaningful industrial co-operation - is still largely unfulfilled. Important partner nations such as Australia, Denmark and Norway have all now expressed very public dissatisfaction at the hand they have been dealt by the JSF Programme Office. Nowhere are these concerns more keenly felt than in the UK, where the unresolved issues that still swirl around the JSF threaten to trip up the programme.
STOVL
Lockheed Martin's most important recent achievement has been the apparent elimination of much of the excess weight plaguing the STOVL design. This emerged as a serious concern in 2003 and the scale of the problem was the source of much speculation. When the actual figure of 3,300 lb overweight was made public (via a written answer to the UK House of Commons in May 2004) it drew a sharp intake of breath from most observers. Some of the worst-case guesses had been confirmed.
However, by early September Lockheed Martin was confident enough in the work undertaken by SWAT, its STOVL Weight Attack Team, to announce that 2,700 lb of "unwanted estimated weight" had been removed from the STOVL variant. Programme officials confirm that the 3,300 lb figure was accurate and that the 600 lb that appear to remain unaccounted for are absorbed by the extra margins the design team has set itself.
The overweight issue was tackled in several areas. One of these was a revision of some of the basic aircraft requirements. While this was described by a senior source as "a pragmatic review of the ground rules and assumptions originally made for the JSF," many outside the programme see the changes as a moving of the goal posts and wonder if the requirement has now been made to fit the aircraft, instead of the other way around. Tom Fillingham, vice president and deputy programme manager for the JSF at BAE Systems, told JDW that many of the assumptions made for the JSF were based on experiences with the Harrier and AV-8 - experiences found to be inapplicable to the new, more modern aircraft.
Fillingham says that 70% or 80% of the weight saving was achieved through a physical redesign that included the relocation of several internal elements within the STOVL airframe. The air inlet and engine nozzle designs were revised to gain extra effect from the 'installed thrust' of the engine, but the basic level of engine thrust has not been increased - contrary to several reports. Perhaps the most important change to the STOVL configuration is a reduction in the size of the aircraft's two internal weapons bays. The F-35B no longer has a common weapons bay with the ability to carry 2,000 lb-class weapons, such as the GBU-31 Joint Direct Attack Munition. Instead, it is now limited to two 1,000 lb weapons, plus an unchanged load of two AIM-120 Advanced Medium-Range Air-to-Air Missiles. As noted below, this is not a positive development for future F-35B operators.
One unexpected boost for the STOVL programme came from US Air Force (USAF) Chief of Staff Gen John Jumper, who announced in September that a possible USAF buy of STOVL aircraft, alongside its existing Conventional Take Off and Landing (CTOL) F-35As, could number "in the hundreds". Gen Jumper said that the F-35B would be an ideal close air support platform for the USAF and his comments followed earlier expressions of interest in the F-35B from Air Force Secretary James Roche. Such support for STOVL is warmly welcomed by the JSF team, coming as it does at a critical decision point for the programme. However, elsewhere it is largely dismissed as manoeuvring for which neither Roche nor Gen Jumper will ever have to sign a cheque. The USAF has nothing resembling either a budget or a concept of operations for a STOVL JSF.
The F-35B has received several other pats on the back of late. A Lockheed Martin press release of 14 September quoted Tom Burbage, company executive vice president and the general manager of JSF programme integration, saying: "The F-35 is now tracking ahead of its Key Performance Parameters, and past concerns about the aircraft's aerodynamic performance have diminished." This was the first time that Lockheed Martin had ever made reference to such aerodynamic performance worries - as distinct from the weight problems - and the question of exactly what was causing such concern was left hanging.
It may be that the JSF design team is now grappling with unexpected drag and other performance inhibitors. Tom Fillingham says that the STOVL redesign forced a trade-off between drag and low observability, and that tunnel testing is still underway to resolve this. He also notes that as the redesign has changed the outer mould line of the aircraft, drag figures in the supersonic and subsonic regimes have changed - but have not necessarily worsened across the flight envelope as a whole.
Within the UK there are several specific concerns around the JSF or JCA (Joint Combat Aircraft) as it is identified there - all of them serious. The doubts that still surround the future of the STOVL aircraft must cause the most worry, as the UK's future carrier plans are so firmly wedded to this variant. BAE's Fillingham believes this is not such a headache, saying: "STOVL selection is not an issue because we are building all three variants and we will provide whatever the customer wants." However, Fillingham underlines that the UK commitment to STOVL may not be total when he admits: "STOVL is not set in stone. Right now our current planning is for STOVL but we don't have a contract."
What lies ahead?
Fillingham confirms that BAE Systems is still planning for a UK buy of 150 aircraft, from the current anticipated US and UK production total of 2,593 JSFs. The figure of 150 JCAs has been used for BAE's costing proposals and industrial planning. This large number now seems wildly over-optimistic - especially when viewed in light of the future combat aircraft force figures released as part of July's defence cuts. The Tranche 2 funding crunch that has stalled the Eurofighter programme stands as a stark warning to what may lie ahead for the JSF.
The UK has already seen readjustments to its delivery and entry into service timetable as a result of the overall delays that have slowed the JSF's progress. Current plans call for the first UK order to be included in the Lot 3 low rate initial production (LRIP) order that is now scheduled for 2009. If it proceeds, this buy will include just two aircraft for the UK with first delivery to follow in late 2011 (delayed from 2010). If more parallels can be drawn from the Eurofighter experience this means that the UK will not have an operationally effective JCA force until 2015, at best.
Furthermore, there is a sizeable question mark over the UK operational road map for the JCA following the reduction in size of the aircraft's internal weapons bays. It is uncertain just how many of the UK's desired weapons options will now fit in the redesigned aircraft, but there are clearly some serious implications. This comes at a time when UK industry (led by MBDA Missile Systems) already faces an uphill struggle in convincing the US to integrate non-US systems in the first place.
It has not always been clear what variant of the JSF the UK will be supplied with as Lockheed Martin and the US government define the standards for the so-called International Partner Variants behind closed doors. Tom Fillingham says that his "understanding" is that the US and UK JSF variants are equivalent, adding: "The Joint Operational Requirements Document is a US/UK document. At an industrial level we are working to a joint US/UK requirement."
Technology transfer
Alongside the 'nuts and bolts' programme matters, the wider issues of technology access and insight remain the greatest hurdles to be overcome by the UK. There is widespread dissatisfaction within UK industry at how the US has controlled such access to date, even with non-classified data.
Meanwhile, agreement on fuller access to sensitive technology, needed to permit proper maintenance and logistics support for the future UK fleet, still remains unresolved. The UK's Secretary of State for Defence Geoff Hoon and Procurement Minister Lord Bach were involved in fiery transatlantic exchanges earlier this year, demanding that the US be more accommodating to its sole Level 1 partner (and investor) in the JSF programme.
So far, attempts to authorise a UK (and Australian) exemption to US ITAR (International Traffic in Arms Regulations) rules governing defence exports and industrial co-operation have proved fruitless. Talks on export reform have been underway in the US since 2000 but heightened concerns for national security have made the House less amenable then ever towards concessions. America's forthcoming elections have shifted any possible agreement well into 2005 - and the political climate that will follow those elections will bring a further effect that is as yet unknown.
The US authorities have not even specified exactly what they consider to be the sensitive elements involved with the aircraft, leaving partners such as the UK working in a vacuum and hoping for the best.
At the heart of the problem is a reluctance to concede foreign access to the internal workings and manufacturing processes of the JSF. Data that is crucial to maintenance and logistic support for the JSF may also reveal many of the aircraft's secrets. All the signs are that when the UK asks for such access it will not be granted willingly - leaving the UK authorities to ponder once more just what they are getting for their $2 billion stake in the programme.
BAE's Fillingham admits that it has not all been plain sailing. "We have seen some successes (with respect to technology access) and then there have been areas of difficulty. We have not been denied access to anything, but it has not been a straightforward process either. The fact is that it's US law and we just have to work within that," he says. "We have to demonstrate our worth every time." Commenting on recent public expressions of dissatisfaction from senior BAE Systems management, he adds: "If my bosses say there is a problem then there must be a problem."
'Answers found to F-35 weight problem' (JDW 22 September )
'Slimmed-down JSF back on track' (Jane's Navy International October 2004)
JSF - current delivery schedule
Development aircraft Delivery due
A1 (non-optimised CTOL) August 2006
B1 (optimised STOVL) mid-2007
A2 (optimised CTOL) late-2007
C1 (optimised CV) late-2008
Note: optimised aircraft incorporate SWAT redesign features.