Graham Warwick/MONTREAL

Lockheed Martin has switched the roles of its Joint Strike Fighter (JSF) concept demonstrators to offset cost overruns on the programme.

The company had planned to fly its first X-35 concept demonstrator aircraft (CDA) in USAir Force conventional take-off and landing (CTOL) configuration, then convert it to US Navy carrier-capable (CV) configuration to demonstrate commonality between variants.

Now, to save money and compress the schedule, CDA number one will be converted to short take-off vertical landing (STOVL) configuration after initial flights as the CTOL demonstrator. This will avoid the time and expense required to fit the CV variant's larger wing control surfaces, fins and tailplane, says deputy programme manager David Palmer.

CDA 2, which was planned to be the STOVL demonstrator, will be completed in the CV configuration. The change is possible because both X-35s were always intended to be able to accommodate the shaft-driven lift fan and other lift system hardware, in case the STOVL demonstrator were to crash, says Palmer. Construction of CDA 2 is now about four months behind that of CDA 1, but the CV X-35 will fly only two months after the CTOL demonstrator because of the extensive ground tests planned for the first aircraft.

The lift system will be installed in CDA 1, and STOVL ground "pit" tests performed, before its first flight. After two months of testing in CTOL configuration, with the STOVL hardware disconnected, the aircraft will be grounded and the lift system reconnected. This will take only about a month, Palmer says, less time than it would have required to convert the X-35 to CV configuration.

The disadvantage of the new approach, says Palmer, is that the CTOL aircraft will be "about 4,000lb [1,800kg]" heavier than planned because of the lift system hardware. "We will have to extrapolate the results of flight testing to the lower weight of the CTOL JSF," he says.

In another move to offset cost overruns, some technology maturation work has been delayed. At the start of concept demonstration, Palmer says, 16 critical technologies and processes were identified that needed to be reduced to low risk by entry into engineering and manufacturing development (EMD). Now only 13 will be reduced to low risk when EMD proposals are submitted next year.

Palmer says the firm has agreed with the JSF programme office that it will complete the risk reduction work in the remaining three areas between submitting its proposal and the EMD shortlist, due in mid-2001. "We have not delayed any of the really critical technologies, such as the lift fan," he stresses.

Source: Flight International