Forum: F-35 Lightning II

Daniel J. Crowley, Lockheed Martin’s vice president and F-35 program manager, said weight is “not something I think about or talk about much because we’re on track to our weight projections.”

Several years ago, he said, weight was a critical issue, as it was cutting deeply into the payload that the F-35B could take off with vertically. The program was allowed a year’s delay as weight-cutting ideas of all kinds were explored and implemented. As a result of the redesigns that ensued, “we’ve been tracking now for several years to a three percent weight growth projection,” which is half of what Naval Air Systems Command anticipated. The weight savings applied to the F-35B provided some bonus payload for the Air Force and Navy versions, although the F-35B weapons bay had to be modified and as a result can only accommodate weapons up to the size of a 1,000-pound Joint Direct Attack Munition. The Air Force and Navy variants can still carry the 2,000-pound JDAM.

“We learned a lot of lessons from legacy programs” and from the F-22, Crowley said, about “structural problems that grew weight,” and these have been avoided. Also, the computer-aided design of the F-35 has allowed for far more precision in building parts—twice the computing capability available during the F-22’s design.

As a result, weight is well understood and thoroughly under control, Crowley said. In fact, he has the luxury of about 250 pounds of weight savings that are ready to go if necessary. For now, though, the additional weight reduction isn’t needed, and implementing the cuts would add cost, so they’re being held in reserve.

The weight purge of a few years ago was so “intensive,” Crowley said, that “there’s not thousands of pounds” of weight left to be saved on the F-35. However, even with a three percent annual weight growth, the key performance parameters, or KPPs, won’t be affected.

“All of our predictions for performance are based on an end-of-life, worst-case” scenario relative to the F135 engine’s power capacity, “so the true performance of the jet, throughout its life, will be much better.”