The US Joint Strike Fighter (JSF) programme office has agreed to trim design refinement efforts to keep Boeing and Lockheed Martin's concept demonstrations efforts within budget and on time.

Revised proposals from the companies in response to programme office concerns about budget overruns and delays have been accepted. As expected, the changes primarily effect work relating to the follow-on preferred weapon system concept (PWSC) rather than the Boeing X-32A/B and Lockheed Martin X-35A/B concept demonstrator aircraft (CDA).

"Both Boeing and Lockheed Martin will still fly two CDAs and demonstrate the critical flight characteristics of the three variants," says the JSF programme office. "There will be fewer formal design iterations of the PWSC that are provided to the government before the final proposal submittal and some technology maturation efforts have been reduced."

It is understood the cutback in PWSC work relates mainly to analytical modelling and simulation. The companies will use the rest of their $750 million concept demonstrator funding to validate flight characteristics of the planned conventional take-off (CTOL), aircraft carrier (CV) and short take-off vertical landing versions.

The X-32A and X-35A demonstrators will be configured initially as CTOL and later CV versions, and are in final assembly at Boeing and Lockheed Martin Palmdale plants. First flights are due in early 2000, with selection of the winning design and award of an engineering manufacturing development contract scheduled by April 2001. For Boeing, the challenge will be to convince the programme office of the delta-wing X-32's relevance to its recently redesigned swept-wing-plus-tail PWSC. Boeing claims its latest 373 configuration is within 95% of meeting the third and final joint interim requirements document (JIRD3). It had planned to refine the design with another four iterations, culminating in a 377 configuration. Boeing plans one more design iteration - 374 - before the end of the contract.

It is unclear how big an effect the restructured programme will have on Boeing's ability to meet the definitive JSF operational requirement document due for release by the end of the year. Lockheed Martin's latest 230-3 configuration appears to be the closest to the final PWSC design, with the company claiming it meets 99% of JIRD3.

Lockheed Martin's major challenge for the remainder of the CDA phase will be to keep its revised programme within budget, after an earlier overspend of $100 million, and demonstrate the aircraft's affordability.

Source: Flight International