Weight Watchers

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

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

On April 7, 2004, the most expensive, ambitious airplane project in history screeched to a halt. Thousands of Lockheed Martin employees tasked with creating the F-35 Joint Strike Fighter found their daily routines broken by a crisis. It had been quietly building for months as engineers cast wary eyes on the weight projections, particularly for one of the three JSF variants, a short-takeoff/vertical-landing fighter. With each review the problem was becoming more evident: The F-35B STOVL fighter was nearly 3,000 pounds over its projected weight.

Lockheed declared April 7 “Stand Down Day,” using a military term that signals the grounding of a fleet for an emergency safety review. Anyone working on any part of any of the variants was called in to a meeting and given the grim prognosis—four years into the 12-year, $276 billion development program, all work would stop until the JSF dropped some weight.

In Washington, D.C., program managers in the Pentagon had “a fair number of soul-searching meetings in the Department to see if we’d ever fix the program,” according to Rear Admiral Steven Enewold, at the time the program executive officer at the Joint Program Office (JPO), which manages the JSF effort for the Department of Defense.

“There was a belief we could get a lot of the weight,” he says. “But there was a disbelief we could get it all.” One team of independent reviewers anticipated that at best, only two-thirds of the excess weight could be redesigned out of the aircraft.

Inside Lockheed Martin’s Fort Worth, Texas facilities, a squad of 550 engineers was formed to do the liposuction. Most of the weight was in the airframe, but with thousands of extra pounds to account for, the innards of the JSF also had to be redesigned. It was everybody’s problem. Directed by about a dozen team leaders, each plucked from his or her area of expertise (airframe, mission systems, engines, and so on), the engineers called themselves the STOVL Weight Attack Team, or SWAT.

Before the team was formed, the SWAT engineers had been watching the penalties imposed by the extra pounds. The F-35B was busting specs on landing speeds, especially in cases where a pilot returned with a full load of unexpended ordnance.

“There was a lot of agreement that the program was in a critical stage,” says Art Sheridan, the current director of F-35 affordability at Lockheed. With SWAT, “the company was putting its money where its mouth was,” he says.

Sheridan knows the F-35 very well. Hired in 1979 as an aerodynamicist by General Dynamics, he has worked at the Texas plant ever since, eventually becoming chief of all STOVL projects. Since 1995, he has served in a slew of positions with the F-35 development team. He was also responsible for analyzing the X-35 flight test data during the JSF contest with Boeing (see “Winner Take All,” Dec. 2002/Jan. 2003).

In April 2004, Sheridan was named leader of the ad hoc SWAT team. The future of the F-35 program and of Lockheed Martin’s stake in military aviation rested on his slight, stooped shoulders. “I had been very vocal about the weight issue [during 2003],” Sheridan says now, a grin stretching the curved geometry of his ash-white beard. “Maybe the way to get back at me was by making it my problem.”

At 8:15 a.m., a flow OF vehicles and people steadily pours into the Lockheed Martin Aeronautics plant, located just outside Fort Worth in the town of White Settlement. Roughly 16,000 employees here design and assemble some of the world’s most complex aircraft. There is a high ratio of blue jeans to suits. These are not the corporate types of the company’s Bethesda, Maryland headquarters, but the brainy designers and blue-collar assemblers of the defense contractor’s products.

The pre-World War II facility, formerly U.S. Air Force Plant Four, has seen the birth of tens of thousands of aviation legends, from the B-24 to the F-16. It has also witnessed expensive stillbirths like the A-12 Avenger. SWAT’s job was to keep the F-35 in the former category.

The cornerstone of the company’s future military aviation business, the F-35 is a complex undertaking: A worldwide network of partner contractors and subcontractors produce components that are assembled in a section of a mile-long building in Texas. Shared three-dimensional electronic design files are updated daily to keep each engineer working on the most current version. At the Texas plant alone, about 4,500 employees work on the three JSF variants, each with unique requirements and capabilities to suit the various needs of three finicky U.S. armed services and more than a handful of skittish international partners. For affordability’s sake, however, the variants must be largely—up to 80 percent or so—identical. Because of the high degree of commonality, modifications to the design of the portly problem child can be applied to the other two versions.

One challenge in designing stealth aircraft is that all stores—extra sensors, fuel tanks, and weapons—must fit internally. Anything hanging outside of the aircraft will increase the aircraft’s radar cross-section and thus diminish its stealthiness.

On the F-35 STOVL variant, the F-35B, the weapons bays must share internal space with an enormous lift-fan engine, which enables the vehicle to hover and land vertically, and with the engine’s ducts. The wide cavities demanded for these components contribute to weight gain because they compromise the best layout for the aircraft’s load-bearing structure. Creating an airplane around these systems is akin to designing a human skeleton after the organs have been installed. It forced the airframe team to adopt a heavier design.

The program’s initial focus on affordability also added weight. Off-the-shelf parts cost less but weigh more because they are not optimized for a fighter. To get bulk quantities of replacement parts for a lower cost might require using a heavier component. It soon became obvious that the plan to use common parts among the variants—a strategy that would lower costs and streamline future maintenance demands—was also bulking up the F-35.

Initial estimates of how much a part will weigh are based on its volume and material. But they are just estimates; the actual weight is another matter. A heftier hose, a wider screw, a thicker panel—in dribs and drabs, the weight steadily increases.

Even in a world of precision design tools, weight estimates still depend on data from previous aircraft. That turned out to be a problem as the crowded interior and the demands of the design translated into poundage. “Legacy estimating techniques just don’t work with this family of airplanes,” says R.J. Williams, Lockheed’s vice president of F-35 Air Vehicle Development.

Art Sheridan says that cost, not weight, was the most important measurement during the early history of the program. “The focus was very much on affordability at the time,” he says. “People realized there was a penalty to be paid, and that was included in the weight estimates. It was higher than we thought.”

No matter the reason, when weight became the enemy, the SWAT team concentrated its effort on reducing it, as well as reducing the bureaucratic hoop-jumping that can slow a redesign. “The number one commitment was to remove obstacles and make quick changes,” Sheridan says.

Instead of the typical series of boards that normally reviewed proposed design changes, SWAT consolidated the process into one review panel. Engineers were expected to come in with an idea, face detractors, and accept a decision in one sitting.

“You’re not supposed to come in with a white coat on,” says Sheridan, and suddenly his face and voice become stern, presenting the manner he used to get the job done. “You’re supposed to come in with a way to make it happen.”

An important attitude change was realizing that all weight savings—a pound here or a dozen pounds there—were vital. According to the database of incorporated SWAT changes, the average recommendation averaged only six pounds. But by taking “only” out of engineers’ mindsets, more and more ideas were considered.

Lockheed engineers like Santi Bulnes, of F-35 Mission Systems and a SWAT team leader, were given a free hand to redesign. “They said, ‘Forget what equipment is in the way. Draw it like you want it,’ ” he recalls.

The process also required a change in parochial attitudes and a willingness to put a finished design up for review, SWAT participants say. No one likes his work questioned, but no one wants a redesigned part to fail, possibly costing lives. Due to the interconnected nature of the airplane’s interior, some new designs required changing perfectly sound ones.

“People are proud of their designs. There is not too much interest in other people’s problems,” says Sheridan, flanked by SWAT team leaders in a Lockheed conference room. Each of the engineers—including Sheridan—had original designs abandoned during the redesign. “It’s a transformation from feeling good about protecting yourself to the exhilaration of pushing that margin out,” he says.

If “exhilaration” seems like a strong word to describe the process, it helps to understand the engineer’s mindset. A radical redesign under extreme time constraints is as challenging as the field gets. “It’s not often you get to spend your days with that talent pool and work problems like that,” says Bulnes. “We probably won’t see it again in our careers.”

Joe LeCompte was a 24-year-old rookie electrical power system engineer on Stand Down Day. His job at Lockheed was his first after graduating from Louisiana State University.

The meetings began only after employees were given some time to think. From the first order— “Everyone go to your cube [to brainstorm] and don’t bother anyone”—he felt grateful to be included in the rescue. “I felt really informed,” LeCompte says. “They had charts showing where the program needed to be. It wasn’t like smoke and mirrors.”

Managers that day announced the financial rewards to be paid when weight-loss ideas were accepted: $50 an idea and an equal amount for every pound the idea removed. The bounty was later increased to $100 an idea and $500 per pound.

The mix of candor, pressure, and incentives paid off: Something “did occur to me on Stand Down Day,” LeCompte grins. What occurred to him was to remove a power panel from the right-hand weapons bay by modifying another to handle the work. If realized, the modification could reduce overall weight by more than 20 pounds.

Four months later, LeCompte was called to a SWAT board meeting, where senior Lockheed officers said his idea would be included in all three variants. They awarded him $13,000. LeCompte used the money to close on his first home.

He says he also felt the satisfaction of directly contributing to the final design of the 21st century’s first new fighter, which, thanks to him, has a reconfigured power panel, as well as three other improvements he suggested, each of which removed about a pound.

It’s one thing to hear company officials speak of a “change in culture” among staff; it’s another to hear it from a fresh-faced 26-year-old. “People realized a half-pound was worth something,” LeCompte says. “Even today, if you’re working an issue and you mention weight, it gets everyone’s attention.”

The deluge of ideas—more than 2,000 were suggested on Stand Down Day alone—initially overwhelmed Lockheed’s F-35 managers. To smooth the process of the redesign, they created a permanent Weight Improvement Program to assess ideas and pay rewards. Staff ffrom every office became “dieticians,” studying every conceivable part on the aircraft for weight.

Steven Twaddle, a materials engineer, realized that he could reduce the surface area of thousands of nut plates by using a high-strength adhesive, which saved 21.5 pounds. Aircraft performance senior staff engineer Brian Losos, who has worked on the JSF since 1995, came up with an idea to change the landing gear housing. Instead of a single door opening from the side, he suggested a two-door clamshell design. It would increase the weight, but the aerodynamic effect of removing the single dangling door, functioning as a sail in crosswinds, would allow a reduction in the size of the two tail fins. The change garnered him a $15,000 bounty.

By the end of February 2006, Lockheed Martin had paid out more than $1.2 million to employees for ideas. The cost is considered minimal compared to the benefits, says Greg Henderson, the inaugural director of the F-35’s Weight Management and Control office at Lockheed.

Whereas the SWAT team had the chance to reconfigure the entire airplane, “the configuration is now fixed,” Henderson says. “Now we ask: What’s the lightest way to make it? Every hole and flange is looked at.”

Hiring Henderson to oversee the effort, and ultimately making the position permanent and directly accountable to high-level company officials, proved how serious Lockheed Martin believed the weight problem to be. Henderson says a high-level position dedicated solely to weight issues is unique in the industry.

Part of the weight management office’s job is reaching out to suppliers. “Post-SWAT, we have to contend with the milling and grinding,” says Henderson. Experienced structural engineers visit supply shops with ideas on changing designs to cut weight. Subcontractor efforts shaved 586 pounds during SWAT.

Keeping the pounds off requires diligence. The weight control office has to combat “bounce back”—the tendency to put pounds back on after they’ve been lost, a familiar pitfall of many a human diet. “They said it was hard to take thousands of pounds of weight off the aircraft,” Henderson says. “But it was considered impossible to keep it off.

“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.

Performance had to be guarded, but the government also wanted to control cost. The F-35 started as the most expensive warplane in history—no one wanted the price tag to increase.

Military customers fretted that the airplane’s maintenance and logistics demands would increase due to the redesign. In response, SWAT included the impact on these parameters in its database of design changes. “We didn’t have those constraints,” Sheridan says. “But we definitely kept an eye on them…. [The JPO] had fear we were going to trash supportability.”

A major blow to the JSF manufacturing concept, leading to an increase in production costs, was the abandonment of “quick-mate joints.” The idea was to attach interlocking parts to individual components that would make the final assembly of the fuselage, wings, and engine easy, like snapping and soldering jigsaw puzzle pieces. But the interfaces drove the weight up by about 1,000 pounds, so a traditional, time-consuming joining system was adopted. All three F-35 variants lost their quick-mate joints to preserve production commonality.

The JSF team had earlier hatched a new idea to cut cost—use “cousin parts” instead of the sometimes heavier common ones. The concept was going to be applied to trim weight as well as cost.

A cousin part is manufactured using the same machine, but the computational design information is altered to produce a part unique to a variant. If a part is designed to handle certain stresses arising only during a carrier landing, it can be remade with the same tool for the conventional takeoff-and-landing variant, with only a minor cost increase. A commercially available part can be shaved to save room, offering, in some cases, a direct route for a hose rather than a circuitous one. Less hose equals less weight. Unique items cost more to manufacture and to replace, but the weight savings sometimes necessitated the higher cost.

Enewold says the production cost of F-35s has risen slightly due to implementations of SWAT plans. The effect on supportability cost is yet to be seen.

In October 2004, the Defense Acquisition Board signed off on more than 500 recommendations, officially making the STOVL weight loss attack team a success.

In eight months, the Lockheed engineers cut a total of 2,700 pounds from the F-35B. The effort also trimmed 1,300 pounds from the other variants. Comfortable with that legacy, SWAT faded, with accolades, into company history, but an estimated 20 ideas a week still turn up in the Weight Improvement Program office.

Design and assembly changes, mostly related to the SWAT recommendations, have cost about $4.8 billion—part of a $6.2 billion replanning to accommodate the additional design cycle required to make the improvements. The replanning forced an 18-month slip in F-35 deliveries. According to a 2006 Government Accountability Office report, since inception, the development costs of the JSF program have increased 84 percent and its timeline slipped by about five years. The STOVL’s final delivery deadline has been extended two years, to 2012.

When AA-1, the first CTOL F-35, rolled out of the assembly building on a gray, misty morning last February, it featured none of the SWAT-era optimizations. 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, Lockheed officials say. 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.

“Weight’s going to be a focus item for this program for the rest of its life,” notes Enewold. He adds that until flight tests are completed, he will worry that the diet has removed some of the aircraft’s “good weight”—the structure that makes the airplane durable. A former Navy pilot, Enewold knows well the punishment an aircraft suffers during carrier operations.

The future of the F-35 is clouded by political battles, international diplomacy, the availability of titanium, a test schedule that overlaps production timetables, and U.S. government worries over transfer of technology to foreigners. But with SWAT, the program has a chance to come to fruition. Without that team, the sight of an F-35B hovering over a carrier deck would have remained the creation of a company artist, relegated to a poster decorating a corporate conference room.


The X-35A, built to validate propulsion and flying qualities for the Joint Strike Fighter, takes flight in October 2000. Lockheed Martin
The first F-35A nears completion in late 2005. Lockheed Martin
Last July, U.S. Air Force Chief of Staff General T. Michael Mosely announced the F-35's official name: Lighting II, in honor of an earlier Lockheed triumph, the P-38. Lockheed Martin

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