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The X-35A, built to validate propulsion and flying qualities for the Joint Strike Fighter, takes flight in October 2000. (Lockheed Martin)

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How a team of engineers and a crash diet saved the Joint Strike Fighter.

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(Continued from page 4)

“Many of the graybeards said, ‘You’re not going to be able to hold it,’ ” adds Henderson, now president of the Society of Automotive Engineers. “But between October 2004 and now [May 2006], we’ve held that flat. It’s historically unprecedented.”

Indeed, skepticism still lingers within the Joint Program Office. After all, it is the job of that office to remain alert to problems. “It was successful in that, for now, we kept the weight off,” says Enewold. “My parting shot is that I’m cautiously optimistic the weight will stay out.”

While Lockheed Martin engineers struggled to trim the F-35’s weight, they also fought to protect the airplane’s performance. However, some concessions had to be made, and Art Sheridan says that members of his team reluctantly approached the defense department with requests to relax some requirements during the redesign. Sheridan calls it “a last resort.” Until engineers can prove why their efforts at another solution failed, he says, a suggestion to diminish performance is bound to go nowhere.

At SWAT’s request, plans for the F-35B to carry a pair of 2,000-pound bombs internally were returned to the aircraft’s original specification of two 1,000-pound bombs. The requirement to carry two internal missiles alongside the bombs went unchanged.

So how does an engineer ask the Pentagon to be flexible? First, keep the military in the loop. Show a graph with the progress so far. Then, according to Sheridan, present the stark truth: “You can look at this requirement, or would you rather not have the program?”

The game of aircraft design is one of tradeoffs, which inspires differences in opinion. Giving everyone within the JPO a say in the redesign would be a recipe for disaster. “No one person’s opinion could grind us to a halt,” says John Hoffschwelle, a SWAT leader and director of F-35 Air Vehicle Definition.

Sheridan says it was a matter of keeping the JPO informed of all changes but limiting JPO involvement as much as possible. “They weren’t really voters” during SWAT, Sheridan adds. Some less diplomatic engineers call it “helping the customers control themselves.”

From the Pentagon’s perspective, there was little choice. The STOVL was not going to fly as designed, and the design talent was all locked up in Lockheed and the other contractors. “The truth is, they have the knowledge,” says Enewold. “When we decided we needed to go after weight, we said [to contractors], ‘There is nothing restricted in what you can look at.’ ”

Still, he adds, the JPO needed to get some decision makers on the scene during the redesign to provide “sanity checks on trades” that were being suggested. A dozen colonels, majors, and upper-level civilian managers stayed in Fort Worth through 2004 to analyze solutions and sign off on program-level changes, something the usual retinue of about 20 JPO liaisons at Lockheed could not do.

Some half-dozen SWAT ideas were rejected, Enewold says. Lockheed engineers suggested reducing the maximum G forces the STOVL could pull, for example, but the JPO insisted it stay at 7 Gs. An attempt to remove some fire suppression generators was also nixed. “Even since then [SWAT], we’ve made some design changes that add a little weight,” he says.

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