An Update on the F-35 Final Assembly Line


2015-01-24 We have published several articles over the years, which have highlighted the approach and challenges of 21st century defense manufacturing, including several on the F-35 production approach.

Recently, Steve Trimble of Flight International has visited the final assembly line for the F-35 in Fort Worth ( and one should note that there is one as well in Italy with several aircraft in production) and will be one in Japan as well.

As Trimble put it in his article published on January 22, 2015:

Mass manufacturing and stealth aircraft have never mixed well. Hundreds of thousands of parts must align at tolerances measured to the thousandths of an inch. A structural misalignment no wider than a few human hairs is enough to make an aircraft shine like a lighthouse in the electromagnetic spectrum.

In the elite club of stealth aircraft manufacturers, Lockheed Martin set the output record six years ago by averaging two F-22 Raptor deliveries per month, then topped that four years later as the F-35 Lightning II production rate reached three per month.

If Lockheed’s order projections are realized, however, the F-35 must become the stealth fighter equivalent of the Ford Model T in less than four years.

That is when monthly output at Lockheed’s mile-long factory in Fort Worth, Texas, is supposed to reach a peak of 17 F-35s in 2019.

Lockheed has built non-stealthy fighters faster in the past – the same factory built 33 F-16s in October 1981 – but the four-year goal for monthly F-35 deliveries is nearly seven times higher than any stealth aircraft program has ever achieved.

Trimble focuses upon changes in the production approach over the past few years and the re-vamped approach going forward.

A key element of understanding the way ahead is his interview with Don Kinard, who has been a key player at Lockheed in shaping the production system for the F-35.

Trimble highlights changes in the approach by quoting Kinard as follows:

Lockheed’s internal position has changed within the last three years, says Don Kinard, a Lockheed senior technical fellow charged with developing the F-35 “fighter production system”.

“We studied [a continuously moving line] for years,” Kinard said in a recent interview. “We did a lot of analysis and we figured that 95% of the benefit of a moving line could be captured with a pulse line. The moving line brought additional complexity to it, and the complexity and the cost of going from a pulsed line to a moving line was determined to be not worth the advantage.”

The F-35’s last stages of assembly will still be very different to those on the F-16 line, for example. Lockheed parks the F-16 after fuselage and wing mating in an assembly bay, where it does not move until the aircraft is ready to enter the paint hangar.

By contrast, Lockheed adopted a “pulsed” line for the F-35, with a flow-to-takt-time assembly model. In such a model, components flow through assembly positions all the way through the supply chain at intervals aligned with the monthly delivery rate.

The key sections of the F-35, which are produced elsewhere and mated at the FAL, are joined via an electronic mating and alignment system (EMAS).

According to Trimble:

Lockheed’s electronic mating and alignment system (EMAS) was developed to solve that problem. The EMAS replaces the large tooling towers that would have been required to mate each variant. Instead, a platform is erected, and all four major sections are lifted by crane into an F-35-shaped space in the middle to be mated.

Each of the sections are digitally mapped and mated synthetically in the EMAS software. This simulation of the mating process is used to predict the number and thickness of the required shims and filler. Too much or too little can cause a stealth-degrading misalignment.

The four sections are initially joined together and inspected to make sure the thickness of the shims is accurate. Then, the EMAS pulls the three mate joints apart so workers can make corrections. The sections are then rejoined to validate the corrections. Finally, the EMAS pulls the sections apart one last time so workers can apply sealants and protective coatings on the interior of the structures.

The labor-intensive process represents the majority of the F-35 mating work, but the EMAS makes it possible to mate all three variants using a common platform, rather than individual tooling towers.

For the complete article, please go to the following link:

And also of interest is the companion piece by Dan Parsons of Flight International who addresses the challenges associated with ramp up of production.

To support a rate of 17 jets per month, the facility will need at least 15 EMAS and five soft mate stations, Kinard says. Whereas the Fort Worth production line currently has 10 final assembly stations – where control surfaces and systems are joined to the fuselage – it will need at least 25 at full rate, he adds.

Lockheed has produced around 120 aircraft for the USA and various international partners since deliveries began in 2011. LRIP 8 will bring the number of aircraft on contract to 216. For comparison, the US Air Force has a total 187 Lockheed F-22 Raptors.

“A lot of people don’t realize how mature this program is,” says Mike Rein, Lockheed’s chief F-35 spokesman. “We’re two-thirds of the way to full-rate production.”

The next 12 months are packed with program milestones. Both Lockheed and the US government’s Joint Program Office (JPO) are eyeing one date with tunnel vision: the US Marine Corps’ 1 July initial operational capability (IOC) milestone. The air force should follow in 2016, and the navy plans to bring up the tail in 2018.

“Over the next couple of years, what we’re trying to do is get all three services to IOC, because if you get all three services to IOC, then a lot of other things are automatically done,” Rein says. “You’ve completed your test program. You have produced the airplanes you need to produce. The international folks are getting their airplanes because our IOCs lead to their IOCs.”

For the complete article, please go to the following link:

Editor’s Note: The video shows the basic F-35 final assembly approach at Fort Worth. It is credited to Lockheed Martin and was published on August 30, 2012.