Outgoing LM F-35 program boss admits to flawed weight assumptions

Outgoing LM boss Burbage mentions that weight assumptions about the F-35 were flawed.

Lockheed, during the early years of the programme between 2004 and 2005, was working on the conventional take-off F-35A variant first because the company did not have the engineering resources to work on all three versions of the jet simultaneously, Burbage says. But company and government parametric engineering models began to show that the weight of the F-35B short take-off vertical landing (STOVL) version of the aircraft was getting too high.

"Somewhere along the way, we made an error in our parametric weight models," Burbage says "Turned out we were predicting the things that we knew about pretty well, the structural parts were pretty close, the small detail parts were pretty close. What wasn't predicted well by the model was stealth and internal weapons bays because the airplane that had those capabilities weren't part of the database."

Actually it could have been as early as 2003 when quick-mate joints (appliances used to make production faster) were thrown away to save 1000 pounds of weight (Bob Cox, Team Seeks Weight Loss for F-35 Joint Strike Fighter, Fort Worth Star-Telegram, June 19, 2003).
Tom Burbage, Lockheed Martin's director of the Joint Strike Fighter Program stated at the time.: "That was the trade-off we had to make to get the weight down." This action threw out earlier, happy assumptions about time needed to produce each aircraft.

It may interest some that when the Boeing X-32 was competing with the later winner of the JSF competition, the Lockheed Martin X-35, that the X-32 had too much weight in the design. The only way it could do a vertical landing was taking off some nose pieces and other things.

And more. The X-32 had weapons bays. Or as a LM test pilot said later of the AA-1, "holes are heavy". The X-35 which won the competition, had no weapons bays. LM was given a free pass on this claiming that risk-reduction of weapons bays had been shown already with the F-22. Yet, the two weapons bays configurations are wildly different between today's F-35 and F-22. A big reason, is because of that STOVL requirement which drives all F-35 variants.

When the AA-1 F-35 test vehicle was rolled out in 2006, one Lockheed Martin official stated: “The weight of this F-35A is greater than what was originally projected, but not so high that the aircraft does not meet key performance parameters. The margins would be very tight—they are not wide, even with the redesign—but it would have made it. Every F-35A that follows will be lighter.”

Good use of words for a spin-machine.

The thin weight margins with today's production aircraft, will always be a concern.

Burbage made no apologies for his years of misleading Joint Strike Fighter Partner Nation government officials about cost and capability of this troubled program.