First flight of the Lockheed Martin F-35 in late 2005 is "reachable", says the Joint Strike Fighter (JSF) programme office, provided weight issues are resolved by June. The just-completed preliminary design review (PDR) indicated the F-35 is about 2% over its target empty weight. Weapons integration issues were also highlighted, but have been overcome, says Lockheed Martin JSF programme general manager Tom Burbage.

Weapons integration issues are mainly centred on deployment of the MDBA Asraam short-range air-to-air missile planned for UK JSFs. The F-35 has two internal weapons bays, and the PDR indicated the door-mounted Asraam could collide with the other munition in the bay during deployment. The solution is to increase clearance by mounting the Asraam on an extending trapeze attached to the door. US JSFs will be armed with externally carried Raytheon AIM-9X missiles.

The weight issue is a result of insufficient maturity of the airframe design and inefficient structural load-carrying, says Burbage, speaking at the Navy League Sea-Air-Space convention in Washington DC last week.

Most affected is the short take-off and vertical landing (STOVL) variant, which is 300kg (675lb) over its target PDR weight. The aircraft is below the weight target for initial operational capability, and below the not-to-exceed weight at which the first key performance specification is affected - for the STOVL JSF, this is the short take-off capability from a flat deck on a hot day, with no wind - "but there is not enough margin", says Burbage.

The PDR will not be finished until Lockheed Martin has closed all 23 critical open action items. Fourteen have been closed, says Burbage, and the remaining weight issues are expected to be resolved by June. Meanwhile, the company is releasing build-to-work packages incrementally in an effort to stay on schedule for the critical design review in April next year and first flight in the fourth quarter of 2005.

Source: Flight International