JSF Team Shifts Course on First Stovl Version

Aviation Week & Space Technology 09/07/04
author: Robert Wall

Optimized Plan

F-35 Joint Strike Fighter managers have again tweaked project plans, this time to speed up testing of a production-representative short takeoff and vertical landing version of the multi-role fighter.

Moreover, representatives of the Lockheed Martin-led JSF industry team are updating the program's schedule and software plans for presentation to senior Pentagon leaders in October. The meeting could put an end to the turmoil the program has been in for more than a year, since developers discovered the Stovl model was more than 3,000 lb. overweight.

When the team initially regrouped after the weight problem was found, it determined the first two of 14 flight test aircraft built during the system design and demonstration phase would have to be in the "heavy" configuration. But the contractors' so-called Stovl Weight Attack Team (Swat) was able to complete most of its work faster than expected, opening up the opportunity for the first Stovl to be in the "optimized" configuration, says Tom Burbage, Lockheed Martin vice president and JSF general manager.

The switch doesn't come without a price. First flight of B1, the first Stovl JSF, would now take place about three months later, approximately late 2007. However, Burbage points out the change eliminates a lot of engineering activity that would have gone into designing a one-off "heavy" Stovl airplane. Moreover, it should make initial flight test data more relevant.

During an informal review last month, the Pentagon gave the green light to the strategy.

The "optimized" B1 will feature a smaller bay for the Stovl version. It has been shrunk about 14 in. and will limit that version of JSF to carrying two 1,000-lb. bombs--the other models will still carry 2,000-lb. bombs. British military officials indicated some unease about the move, but Burbage says the design change was put to a vote. All Stovl customers--the U.S., the U.K. and Italy--approved the decision. B1 will also feature a redesigned top inlet used during hover and a smaller diameter lift nozzle. Both changes make the engine more efficient and help mitigate weight.

Production of the B1 will begin in late 2005 with the fuselage section at Northrop Grumman, says Steven Briggs, Northrop Grumman's JSF manager.

The weight reduction effort has shaved more than 2,700 lb. from the aircraft, and generated additional savings by relaxing performance requirements. As a result, the program has weight margin going forward, Burbage says.