Lockheed Martin is finalising a revised Joint Strike Fighter (JSF) design that should help overcome a 1,360kg (3,000lb) weight problem already blamed for a two-year delay and a $5 billion cost overrun.
But design changes alone will not be enough to scrape off the balance of the excess weight. Lockheed Martin is also proposing methods to increase propulsion efficiency and tweak the F-35B short take-off and vertical landing (STOVL) version's performance requirements, says Dain Hancock, president of Lockheed Martin Aeronautics.
The combined improvements, due to be reviewed by the F-35 Joint Programme Office (JPO) in mid-August, "effectively eliminate" the weight issue, and may offer surplus margin, says Hancock.
About two-thirds of the weight savings can be reached by directly taking mass off the airframe, says Rear Adm Steven Enewold, who became JPO director last month. In recent months, programme officials have discussed spacing out the aircraft's wing ribs as one way to trim weight.
The balance of the weight problem - roughly 450kg - also can be partly addressed by improving the efficiency of the STOVL aircraft's engine and liftfan. But the programme is "holding the line" on improvements that increase temperatures within the engines, which would reduce the operational life of the propulsion system.
The final category of changes involve tweaks to performance requirements. One example is to reduce the wave-off pattern for aborted carrier landings, trimming the fuel reserve requirement of dozens of kilograms. "We're doing a sanity check on performance requirements," says Enewold. "We have to grade ourselves on the way the aircraft is really used."
STEPHEN TRIMBLE / FARNBOROUGH
Source: Flight International
