Lockheed Martin has further refined its Joint Strike Fighter (JSF) final design to cut weight and improve the aircraft's payload bringback performance, while it battles delays in the start of flight testing of its two concept demonstration aircraft (CDA).

The company is due to complete the reconciliation of its final Preferred Weapons System Concept design iteration 235 against the JSF programme office's (JPO) latest operational requirements document by 22 July. To this end, Lockheed Martin and its partners BAE Systems and Northrop Grumman have made further changes to the last 230-5 design.

"We're short on bringback weight," says Frank Cappuccio, Lockheed Martin JSF programme director. "We claimed we brought back 6,500lb [2,950kg], while the government claimed we brought back 4,500lb. The specification was 5,000lb. Rather than get into a big discussion, we modified the structure and got about 500lb out."

Weight has been trimmed across areas such as the bomb bay and landing gear doors, rather than in one major system or substructure. The company has refined systems such as actuators, software fusion and electrical generation, while the PWSC's canopy has been strengthened for improved birdstrike protection.

"We're starting to refine the guts of the aircraft, with much of the effort being spent on refining suppliers bids," says Cappuccio. Lockheed Martin says its PWSC is within 8% of being reconciled with the JPO on cost and 10% on projected engineering manufacturing and development costs. It calculates that the conventional take-off landing version (CTOL) will cost $27.9 million per unit, while the government estimates $28.9 million.

In risk reduction terms, Lockheed Martin says the short take-off vertical landing (STOVL) version is in the "green" meeting range, manoeuvre and basing requirements, while the CTOL and aircraft carrier derivatives in many cases are "blue" or exceed requirements. Around 80% of weapons have achieved a 50mm (2in) or better weapons bay clearance, but are falling 13mm short of accommodating the Matra BAe Dynamics Asraam and Alenia Marconi Systems Brimstone missiles.

The first flight of the CTOL CDA has been delayed by software regression and is now set for late July. "I think the STOVL aircraft will be available by December or even the first of the year," says Cappuccio. The final proposal is structured to be able to submit data until 1 March, with the final downselect due around late April.


• Boeing has started taxi trials of its X-32A JSFCDA. The tests - in which the aircraft reached 55kt (100km/h) - verified function and integration of steering, braking, engine controls and flight-control surfaces while the aircraft was in motion.

Source: Flight International