OEMs using new technology to speed up aircraft assembly

 - February 2, 2007, 9:57 AM

With the Falcon 7X, French-based manufacturer Dassault has cut in half the time it takes it to build the first example of a new top-end business jet. The company is using digital design and construction tools to streamline the assembly process. At the same time, lower development and production costs have a favorable effect on the price of the 5,700-nm trijet, Dassault claims.

Experts say new business airplanes developed from this point on will benefit from the techniques Dassault is pioneering today with the Falcon 7X.

In mid-December, the first 7X was undergoing system testing at Dassault’s Bordeaux-Merignac final assembly facility. It was being prepped for vibration tests and the first ground run took place on February 1. A rollout ceremony was planned for the middle of last month. “We are perfectly on time,” Jean-Marc Grillet, senior v-p for industrial operations, told AIN. According to a “7X update” video released last fall, the company even exceeded expectations in terms of manufacturing speed and accuracy.

Construction of the first Falcon 900 two decades ago took 14 months versus just seven months for the new 7X. Those gains come from a wide-ranging strategy, including a major effort on information systems with the use of the Catia design software.

“We also managed the various skills in an exacting way,” Grillet said. Using a “minimum-risk overlapping” industrial process, the company began manufacturing parts before the aircraft’s design was 100 percent complete. “Our priority was quality, cost and cycle time for producing parts. We had a slight overcapacity and almost no subcontractors during this phase,” Grillet explained. The opportunity allowed a production cycle time of only 15 days for a new sheet-metal part.

Asked about time savings once the assembly line reaches its nominal rate, Grillet said that the production cycle for green aircraft will be shortened by one month, to one-and-a-half months.

The completion cycle, he added, will also be reduced by one month. The current cycle is four to five months, depending on customer specifications.

Last September, Dassault officials pegged the development costs for the 7X at “20 to 50 percent” less than for previous Falcon programs. Part of the saving results from the fact that the design software made it unnecessary for Dassault to build either a mockup or a prototype of the 7X. Three fully conforming production aircraft will be used for the flight-test program and a fourth will be used for structural tests on the ground.

Employing Digital Designs
Digitization started early in the design process. Right after program launch, Dassault gathered all the risk-sharing partners on a “plateau,” a giant open-space office at its headquarters in Saint-Cloud, near Paris. Some 350 engineers worked concurrently on 250 design stations and began the aircraft’s virtual construction. They used a single software basis– Catia for design and Delmia for production.

They then returned to their home bases in Canada, France, Spain and so on to continue the design work using the same tools. During this “virtual plateau phase,” they were linked via a dedicated network and could quite literally be on the same page.

The machines that make the 7X’s parts use the same data that designers saw on their screens, resulting in an unprecedented level of accuracy in parts manufacturing for the entire airframe. Parts now fit perfectly, which has streamlined the assembly process, said Dassault.

Conventional, complex tooling has disappeared. Using the digital design and its Delmia production software, Dassault tasked robots to pre-drill all parts before the assembly stage. As a result, assembly is being conducted on much simpler tooling than that required for previous aircraft, with parts being assembled with adhesives before the installation of rivets into the pre-drilled holes.

The new methods have eliminated the need for time-consuming adjustments. Usually, most holes are drilled during assembly because the exact size of the final part can vary and holes need to be carefully positioned relative to the two parts to be joined. This involves big tooling that needs qualified operators. Now, the existence of positioning holes makes such large tooling unnecessary.

Did Dassault design a virtual-reality factory to optimize the real one? Not really. “This would have been useful if we had a lot of tooling, but we need only a hangar with air hammers and hand drills,” Grillet pointed out. Such an easy assembly phase allows the process to be subcontracted if necessary. “Should the production rate increase, we would use subcontracting as a workload adjustment variable,” Grillet explained. The production rate will start at one aircraft per month.

Relocation of some assembly work into countries with low labor costs is possible, but Grillet claimed to have no firm plan for such a move. According to current plans, “Ninety percent of the Dassault portion of the Falcon 7X will be made in Dassault-owned factories,” Grillet asserted. The company’s share of the airframe work on the 7X is close to 50 percent, with the rest divided among the risk-sharing partners.

The workers who assembled the first 7X discovered fewer than 100 structural conflicts despite the aircraft’s 30,000 parts, 300,000 fasteners and 15 miles of wiring. “Usually, you have five or 10 times more clashes than that at this stage,” Grillet told AIN. Yet Aircraft s/n 3 is fully production conforming because it addresses the issues engineers discovered on s/n 1 and s/n 2.

Interior Completions
Are all these production improvements applicable to the cabin interior completion? “We are going to try to apply our new methods to the completion phase. But customization limits the applicability of the process as there is no standard aircraft,” Grillet pointed out. Therefore, the company will emphasize flexibility. “We will take into account the whole range of options to make the airplane easily adaptable,” Grillet said. For example, some pre-wiring work will simplify installation of several optional items. The company will implement the strategy in the French factories and at the Little Rock, Ark. Falcon completion facility beginning with aircraft s/n 3.

For customers, the pleasure of choosing the interior layout, furniture and colors for their new jet may intensify because Dassault has streamlined that process, too. “The design time of your interior has been reduced from weeks to days,” the Dassault video boasts. In a single session, the customer can define specifications according to a budget and delivery schedule. Every component of the cabin interior appears in 3-D “as it will be in reality, thanks to advanced design tools from Catia,” the video notes, insisting the customer can expect “no surprises.”

Do new processes translate into benefits for day-to-day operations? Dassault is introducing the 7X as the first business jet to be “fully life cycle optimized.” As a result, the manufacturer and the maintenance community may watch the entry-into-service phase even more closely than usual.

A key element of the entry-into-service phase is the ease of performing maintenance tasks. The virtual-reality design process allowed Dassault engineers to plan even this stage. Engineers could simulate full-scale tool handling and human interaction in three dimensions. In other words, every hatch is accessible and every tool fits easily where it has to–unless the program manager decided against maintenance convenience to address another design issue.

In addition, engineers used the design technology to consider ergonomics early in the design phase. For example, the software helped them to consider the optimum position for the pilot relative to the stick and engineers studied accessibility and visibility accordingly. “Everything in the human-machine interface has been anticipated,” according to Dassault.

Grillet explained that customers will benefit from reduced production costs, noting that the current $37 million list price “is only 10 percent more than that of the Falcon 900EX.” He added that production costs for the first 7X have been on target.

Friction Stir Welding
Dassault may have simplified the way it installs rivets, but Eclipse Aviation is getting rid of them altogether by using friction stir welding to replace rivets in more than 60 percent of its Eclipse 500 very light jet. The Albuquerque, N.M.-based startup will be the first company in civil aviation to use FSW for production. Eclipse has completed FSW assemblies for four entire aircraft and two have flown. The process faces a hefty manufacturing task, with Eclipse claiming orders for some 2,200 aircraft.

Eclipse touts numerous benefits of friction stir welding. First, the airframe structures are stronger and lighter than those built using traditional processes. The company says that extensive testing has proved that friction stir welds are up to three times stronger than single-row riveted joints with comparable fatigue resistance and durability. The FSW process also makes for a smooth exterior surface that yields more than aerodynamic benefits by reducing the time and labor necessary to prepare the surface for painting.

How does friction stir welding work? To make a lap joint (as used on the Eclipse 500), a spindle adjoined to a rotating tool is pushed through the first piece of aluminum and partially through the second. The spindle is rotated and pressed, creating frictional heat between the two metals. The frictional heat softens the aluminum without actually melting it, allowing the spindle to stir the two pieces of aluminum together. The plasticized material is transferred from the front of the pin tool to behind it as the tool moves along the joint.

The Eclipse 500 airframe uses FSW skin panel assemblies in the cabin, aft fuselage and wing. “The number of FSW skin assemblies has increased from seven on the first airframe to 11 currently,” an Eclipse spokesman told AIN. The biggest issue, he said, was aligning the skins, frames and stringers in the various FSW tools. But the process has worked well enough that the initial skin welded in each tool has been airworthy.

Eclipse claims to have advanced the state of the aircraft manufacturing art on several fronts, among them the development of a corrosion-protection system for FSW lap joints; development of tooling for large, complex-contour FSW assemblies; and development of structural analysis methodology for FSW aircraft assemblies. The FAA has approved Eclipse’s FSW process specifications.

Asked to estimate production cost and cycle time reduction, an Eclipse spokesman answered that skin panels are joined four times more quickly than with automatic riveting equipment, which translates into a 75-percent reduction in cycle time and
a similar reduction in the capital expenditures required for equipment. With such significant benefits, Eclipse will probably not be the only manufacturer to use friction stir welding. In fact, Airbus is already known to be studying this technology for fuselage assembly.

Business Jet Manufacturers Slow To Use New Materials

Did the commercial failure of the Beech Starship cool business aircraft manufacturers’ enthusiasm for using new materials such as composites? Big airliners in development, notably the Boeing 787 (née 7E7 Dreamliner) and the Airbus A380, will certainly reap benefits from using various kinds of composites. But the trend is not as strong in business aviation.

Raytheon Aircraft is the only business-aircraft airframer that seems to have convinced itself of the business case for wide use of carbon-fiber composites. Both the Premier I and the Hawker Horizon have composite fuselages. For example, the Premier I’s fuselage, whose walls are less than one inch thick, allows 35 percent more cabin volume than competitive aircraft, the manufacturer claims. The fuselage contains no rivets, which reduces drag. In addition, according to Raytheon, the fuselage is lighter, stronger and less dense than traditional metal fuselages. The epoxy resins are highly resistant to water, fuel, oil, antifreeze and most other solvents used in the aviation business.

However, despite these advantages and the fact that Boeing has decided to use this material for the 787’s fuselage, no other business aircraft manufacturer appears to be ready for extensive use of carbon-fiber composites. “Their use will probably remain limited,” Jean-Marc Grillet, Dassault’s senior v-p for industrial operations, emphasized when asked about those materials. He explained that composite materials are slightly more expensive than traditional metal to acquire and manufacture. However, the bigger the part, the smaller the cost difference with its metal equivalent. Therefore, it is easier for designers to use composites on big airliners.

“Aluminum alloys remain competitive, although there are a few exceptions,” Grillet explained. One of these exceptions is the vertical fin. On the Falcon 7X, it is made of carbon epoxy fiber under a resin transfer molding process that provides better strength, a reduced part count and lower weight than metal. “One day, there will be all-composite Falcons, but that day is at least 10 years from now,” Grillet told AIN.

Aluminum-glass Hybrid
Meanwhile, another material seems to be of special interest to designers at Gulfstream. It is Glare, a material mixing glass fiber and aluminum that Airbus uses on the A380. Dutch-based Stork Fokker is Airbus’ supplier for Glare components. It is also a Gulfstream partner–the company builds the tail for the G500 and G550.

On the A380, vast panels of the upper fuselage are made of Glare, a hybrid material, shaped during manufacture for each application and constructed by bonding alternating layers of aluminum and glass fiber. The combination of material properties produces a weight saving of 15 to 30 percent. Other advantages include fatigue resistance, impact resistance, fire resistance and lightning strike capability.

Fatigue resistance is a major drawback of conventional aluminum alloys against new materials. On Glare-made parts, fatigue cracks occur in aluminum layers only, starting in the outer aluminum layers. But the glass fibers stay intact and bridge the fatigue crack, which yields a slow crack propagation rate and high residual strength compared with aluminum alone, Glare promoters claim.

Gulfstream has not talked officially of any plan to use Glare yet.