Rival Joint Strike Fighter teams face challenges to complete the concept demonstrator phase within budget
The Joint Strike Fighter (JSF) competition has become a contest of diminishing resources, with both teams overspent but determined to complete the current concept development phase within budget.
Neither Boeing nor Lockheed Martin appears to want the ban lifted on spending company funds on the programme, fearing this would overturn any perceived advantage one has over the other. They may also be keen to avoid attracting Congressional scrutiny of what has so far been a model programme.
Just past the halfway point in the four-year JSF concept demonstration effort, Boeing is in the better financial state, projecting a budget overrun of "less than 5%", which it intends to have eliminated by the end of the current phase. The company admits, however, that the recent revision of its JSF design increased risks, as well as costs, and that it still has work to do to meet all the JSF operational requirements.
Lockheed Martin's budget overrun is far larger, reportedly at least $100 million, but the company says it intends to execute the concept demonstration phase on schedule and within budget. On the plus side, Lockheed Martin says its JSF design, which has remained relatively unchanged, is now "very close" to the configuration that will be proposed in 2001 for the JSF development and production phases.
Revelations of redesigns and overruns have raised the stakes in what was planned from the outset as a winner-takes-all contest to produce almost 3,000 aircraft for the USAir Force, Marine Corps and Navy, and the UK Royal Navy. With exports expected to boost production to 5,000 aircraft, the JSF programme is estimated to be worth $500-700 billion over 40 years.
It is not surprising, therefore, that, in the light of current problems, the US Department of Defense is re-evaluating its acquisition strategy. The JSF programme office confirms that government and industry "are taking some time to assess the situation". An announcement is expected in mid-March.
Boeing took the wraps off its JSF redesign earlier this year, admitting that it had been unable to meet the evolving JSF requirements with its original delta-wing configuration. There were three main reasons for the switch to a swept-wing design with conventional tail, says deputy programme manager Mike Heinz - weight, pitch control and growth.
Both teams are refining their designs again as the operational requirements are evolved by the customers. Each configuration version reflects a refinement of the joint requirements. Boeing's latest design is configuration 373; Lockheed Martin's is configuration 230-3. Four further iterations are planned before the teams submit development and production proposals in 2001.
Boeing's JSF programme manager, Frank Statkus, says the company recognised late in 1997 that its design - then configuration 372 - was too heavy to meet the JSF requirements. It launched a redesign and produced an interim tailed-delta configuration - 372.4 - before switching to the current swept-wing design towards the end of last year.
Statkus says the combination of swept wing and separate horizontal tail is lighter because of the weight of the large actuators required to drive the trailing-edge pitch control devices on the original delta wing. Although done principally to reduce weight for the short take-off and vertical landing (STOVL) variant of the JSF, the change also increased pitch control for the carrier-based (CV) conventional take-off and landing (CTOL) variant. The chin inlet was changed from forward swept to aft swept and cockpit and vertical tails were reshaped to save weight. The wing and horizontal tail leading and trailing edges were aligned to reduce radar cross-section.
The redesign retained the high commonality between variants that has been a hallmark of Boeing's approach. Compared with the baseline CTOL version for the USAF, the USMC/RN STOVL variant has a slightly reduced wingspan, while the CV version for the US Navy has outboard ailerons. Boeing hopes to eliminate leading-edge vortex fences added to the CV version to improve carrier approach characteristics. Commonality is at "around 90% by weight", Heinz says.
Although the redesign increased the costs and risks of the work still to be done, Statkus says Boeing intends to complete the concept demonstration phase within budget. Assembly of the two X-32 concept demonstrators is under budget and ahead of schedule, he says, and this could let funds be shifted to refinement of the JSF preferred weapon system concept (PWSC).
Statkus believes configuration 373 is so close to the final design that the remaining iterations could be less costly than expected. The objective of the latest redesign was to be at least 90% compliant with the latest version of the JSF requirements. "The programme office says we beat that requirement," he says.
The progress to date may be Lockheed Martin's saving grace. Deputy programme manager Harry Blot estimates that the company's latest configuration, 230-3, meets "99% of the JSF requirements". The company could yet save money on PWSC refinement.
But Boeing still faces weight challenges, says Statkus. "We do not meet the STOVL bringback requirement exactly. The way the programme office calculates weight, we are not quite there. The issue is thrust minus weight. To improve the fuel and payload, we have to find more thrust or less weight. We do not want to operate on the propulsion system, so we will operate on the weight. We will not have a problem, but we are not there yet," he says.
Blot, meanwhile, says the Lockheed Martin design does meet the STOVL bring-back requirement. The company has its own challenges, however, not least in developing the Rolls-Royce Allison shaft-driven lift fan for its STOVL variant, which is responsible for about one-third of the cost overruns. Another third is attributed to errors in accounting for work subcontracted out by Lockheed Martin Skunk Works, which is assembling the two X-35 concept demonstrators.
Lockheed Martin's overruns are on the concept demonstrator portion of the current phase, which makes up between two-thirds and three-quarters of the work to be done under the $1.2 billion contract awarded to each team in 1996. Refinement of the PWSC makes up the balance. This suggests that Lockheed Martin will have to make deep cuts in either or both activities to come in within budget.
Lockheed Martin declines to comment on how it will bring its programme back within budget. Instead, it emphasises the close resemblance between its demonstrators, the current configuration and the design expected to be proposed for the development phase. This is intended to deflect criticism by highlighting a problem now faced by Boeing - that its demonstrators no longer reflect the JSF configuration that will be proposed for development.
Statkus acknowledges this, but says the X-32s will still meet the three objectives of the current phase, demonstrating commonality between variants, STOVL hover and transition, and CV low-speed flying qualities. Because the CTOLX-32A and STOVL X-32B are being built with the same tooling, he believes the first objective has been demonstrated.
As for the other objectives, Statkus says the X-32s will validate the models used to develop control laws for the vehicle management system that will determine how well Boeing's JSF approaches a carrier deck or moves between vertical and forward flight. "We added the tail to get more pitch control power, but the modelling of the tail [in the control laws] is the same as that of the trailing edge of the wing. The tail provides more control to the deck, and the model should show that-all we have to do is prove that the model works. The X-32 will be tougher to get on the deck; the 373 will do better," he says.
Lockheed Martin revised its JSF design about a year ago to improve its carrier suitability, but Blot says the X-35s will be "almost indistinguishable" from the PWSC. The previous 230-2 configuration was heavier and digressed more from the planned demonstrators.
Lockheed Martin has taken a low-risk approach from the outset, and says its decision to adopt a conventional tailed configuration - resembling a scaled-down F-22 - has given it the flexibility to accommodate design changes as the JSF requirements have evolved. The CTOL and STOVL variants share the same wing, while the CV version has larger leading and trailing edge surfaces and tails.
Boeing admits that one reason for its redesign was a lack of flexibility in the original delta-wing configuration. The new tail design provides a wider centre-of-gravity range and greater flexibility to accommodate changes in requirements and future growth, Heinz says.
Both teams believe they have arrived at outer mould lines that will change little, unless the requirements change. "We know we have the right aerodynamic configuration, and we're starting to shift our emphasis from this to our mission systems, lethality, supportability and affordability," says Blot.
This may be where cuts have to be made. Even Statkus, facing a smaller budget overrun, admits: "I believe there is not any more money. There is no option but to make the cost line."
Source: Flight International
