Newly completed redesign and use of smaller weapons bays rule out internal carriage of 900kg-class munitions

Lockheed Martin will revert to 450kg (1,000lb)-class weapons bays in an effort to reduce weight on the F-35B short-take-off and vertical-landing (STOVL) Joint Strike Fighter variant in perhaps the most dramatic change under a newly completed redesign that will allow the aircraft to meet weight targets at entry into service.

The decision rules out internal carriage of 900kg-class munitions, a sensitive issue for STOVL customers the US Marine Corps and UK Royal Air Force and Royal Navy. JSF executive vice-president and general manager Bob Elrod notes such weapons can still be carried on external hard points for missions that do not require stealth.

Elrod also notes that a redesigned weapons bay still complies with customer requirements. The USMC's baseline design only calls for 450kg weapons bays. They were expanded several years ago as a potential performance bonus. The large weapons bays for the STOVL aircraft also increased commonality with the F-35A conventional take-off and landing (CTOL) and F-35Ccarrier variant (CV) in development for the USAir Force and US Navy, which can both carry 900kg-class munitions internally.

Design commonality, a key driver for the programme's affordability goals, will probably suffer from the decision. Lockheed Martin plans to complete weight-reducing redesigns for the CTOL variant within a month and the CV variant by end-year, but Elrod says neither are likely to drop the larger weapons bay.

A year-long focus on weight reduction has led to other manufacturing trade-offs. Last November, it was revealed that Lockheed Martin had abandoned its quick-mate assembly strategy in an effort to save about 360kg.

In total, the STOVL redesign will slash about 1,180kg off the fighter's 13,600kg empty weight, says Elrod.

In another design change, the company has altered the location of the mate joints between centre fuselage and wing. A separate effort to clarify the ground rules for the F-35B's bring-back fuel load requirements allowed the programme to save another 225-270kg, says Elrod.

Assembly work has begun on all four major sections of the JSF. BAE Systems has loaded the aft fuselage into an assembly rig in the UK. Lockheed Martin began final assembly on the wing in Fort Worth, Texas last week and has started work on the forward fuselage and cockpit. Northrop Grumman began mid-fuselage assembly earlier this year.



Source: Flight International