"Joining the Pieces," Feature Article, December 2005

joining the pieces

Engineers are choreographing the assembly of the Joint Strike Fighter.

This article was prepared by staff writers in collaboration with outside contributors.

from its inception, the F-35 Joint Strike Fighter was to be a single aircraft platform for deployment by the U.S. Air Force, Navy, and Marine Corps. But the services' different missions required variants of the F-35 airframe and structure.

The Air Force needed a tough, lightweight aircraft that could operate from fields close to combat zones. This is the conventional takeoff and landing variant.

The Marines needed a plane with short takeoff and vertical landing. This aircraft, which has a 50-inch-diameter lift-fan behind its cockpit powered by the F-35's turbine engine, has also been ordered by Britain's Royal Navy and Royal Air Force.

The U.S. Navy required an aircraft carrier version of the F-35, with larger wings and control surfaces, and a beefier, more rugged airframe to serve on carriers.

In the past, the services would have bought different airplanes, each running up hundreds of millions in one-time costs. One design to suit the three services had appeal, but it also presented engineering challenges.

All the plane's hardware, in all its variety—weapons, radars, fuel tanks, electronics, and the rest—must be shoehorned into the fuselage or wings. Nothing can be bolted beneath the wings or attached to the nose.

The big design issues have been settled. Now, Lockheed Martin, which plans eventually to build an average of a plane a day, is engineering the assembly of the F-35.

The company is building the first of 22 pre-production models of the fighter at a plant in Fort Worth, Texas, where it is studying assembly procedures so that everything works efficiently when production picks up speed.

By simulating the assembly of the Joint Strike Fighter's major components, engineers can forestall problems on the floor of the plant.

Manufacturing engineers are using software from Delmia to study simulations of assembly processes. Delmia, based in Auburn Hills, Mich., is a unit of Dassault Systèmes, whose Catia software is the CAD system that Lockheed Martin uses.

According to Kevin Albers, the manufacturing engineer who manages the F-35 modeling and simulation efforts at Fort Worth, "All of the critical assembly sequence operations have been simulated." Completed simulations include the full assembly sequence for the wing, and the automated mating of the wing structure with the sections of fuselage.

Assembly of the F-35 at Fort Worth has been highly automated and centers around three assembly systems. The biggest of them assembles three variants of wings. Standing about 30 feet high, the assembly systems automatically accommodate different components. One reason for many simulations was to engineer optimum ways that components will go into these systems and the way finished assemblies will be taken out.

Subcontractors and other Lockheed Martin plants are handling most of the detailed parts fabrication and subassembly. The large aircraft components—like fuselage sections and tails—arrive as subassemblies weighing hundreds or even thousands of pounds. Assembly is simplified (and greatly speeded up) because the subassemblies arrive at Fort Worth "stuffed"—that is, with nearly all the system components installed.

The plant is a mile long and in many places several hundreds yards wide, but it's a busy place. Engineers want to be sure ahead of time that they have allowed the required clearances for moving parts across the floor collision-free.

According to Albers, "Even for well-planned manufacturing operations, the simulations reveal some manufacturing issues where you discover a problem with the assembly order, or that you need a tool to locate a part, or a platform or stepladder to reach something. We are finding smaller and smaller problems, which is a good thing. That means the earlier simulations have already solved the bigger problems."

Lockheed Martin plans to begin low-rate production in 2007 and to build 500 planes before full production starts in 2012.