The Airbus A380 is the most modern, spacious, and capable civilian aircraft ever. The project was launched in December 2000, christened “The Flagship of the 21st Century,” and developed in close cooperation with air carriers, airports, and air traffic authorities.
The A380 incorporates the most modern technologies in terms of materials, systems, and industrial processes, adhering to the strictest international standards for registration approval. Airbus’ European sites in France, Germany, the United Kingdom, and Spain participate in the design and assembly of the A380 aircraft.
The Jean-Luc Lagardère site in Toulouse was specially constructed for the A380, and final assembly takes place there. The assembly line for the youngest Airbus consists of several segments. The first unit deals with the assembly of the weight-bearing parts of the aircraft. The second unit conducts tests on the assembled aircraft and installs the powertrains. The third unit conducts the open-air tests that prepare the aircraft for its first flight.
A challenge for the assembly
Station 40 of the first unit is in charge of the final assembly of the aircraft (both segments and wings). For this purpose, different parts are compared to one another. Strict part geometries have to be adhered to. The project for the assembly of the A380 was begun in 1998. Numerous new challenges had to be mastered: The extraordinary size of individual segments, the oval shape of the aircraft itself (the fuselage is round on other aircraft), double-decker fuselage, and so on. Further, assembly tools have to be adjusted with very high accuracy to allow for the final assembly of the aircraft, and they have to be inspected regularly, because they guarantee the correct positioning of different plane segments in 3-D space.
The basic concept behind the new assembly method was to inspect the aircraft directly, that is, to inspect its individual segments in relation to one another rather than to use the tools as a reference system, avoiding the issue of compounding tolerances. The second task was to find a solution for assembling complex interfaces (i.e. the oval shape of the fuselage and the double-decker aircraft layout). The concept of assembly based on laser-based measurements was selected by the executives in charge of the A380 program.
“The challenge of this task had gone well beyond typical assembly. We needed to come up with a common aircraft reference system for all European Airbus sites. Different sites had different working methodologies, their own goals and their own constraints. The preparatory stage was crucial in making sure that the data from various sites are mutually intelligible,” says Thierry Fabre, who’s in charge of laser-based measurements at the Toulouse site.
Selection of Leica Geosystems: logical step
Numerous projects involving Leica Geosystems laser trackers had taken place in the past on various Airbus sites in France, as well as in Bremen, Germany, and Broughton and Filton in the United Kingdom.
“The first projects on Airbus fuselage assembly using laser measurements were developed in close cooperation with the Leica Geosystems headquarters in Switzerland,” explains Martial Charraud, who had previously worked on the sites in Nantes and Toulouse (A320) and is part of the Thierry Fabre A380 team. “Having had very positive feedback based on past measurement jobs, we of course approached Leica Geosystems when we were looking for a solution for the work to be done on the A380n.,”
The A380 assembly line will be used for 30 to 40 years. This makes selecting good, long-term, dependable partners all the more important. The systems used, especially computer software and automation software, are made obsolete very fast. “Serviceability of old systems is extremely important. We have agreed to long-term cooperation with Leica Geosystems. We have a guarantee that if our instruments are subjected to extreme environmental conditions, they will still function as specified,” Fabre emphasizes.
Preassignment of line-of-sight
After installing the tools and settling on the adjustment methods, the laser tracker line-of-sight in very tight quarters had to be analyzed with CAD software. Due to a large number of platforms and structures making up the assembly line, it’s very difficult to guarantee the availability of line-of-sight between measurement points and the laser tracker. “We had to come up with a concept that determines the number of laser trackers needed and the optimal position of each individual laser tracker. This was a particularly challenging task,” continues Charraud.
At first, four Leica laser trackers were chosen—two for the fuselage and two for the wings. All four laser trackers were intertwined and connected by a common coordinate system. This arrangement guarantees the uniformity and mutual interchangeability of the laser trackers.
A simplified human-machine interface
Because the measurement system is integrated into the fuselage assembly process controlled by the assembly workers, they were involved in the development of the human-machine interface from the very beginning. The overall goal was to make using the measurement instruments as simple as possible, especially because most users aren’t metrology specialists. To make assembly tools as simple as possible, complicated processes had to be taken care of beforehand: Automatic control and target location, on-screen result display for determining the correct part positioning, and so on.
Final measurement equipment inspection and adjustment before the first plane was built
An added difficulty of the project was the fact that the entire measurement system had to be inspected even before the first aircraft was present on the assembly line—neither fuselages nor wings were available. Test and inspection procedures had to be developed that effectively simulated the dimensions of the aircraft. The first aircraft—MSN 01—allowed the team to inspect the entire measurement system in a 1:1 scale.
“Permanent improvements and the increases in the output mandate even better dependability and improvements to the aircraft-segment positioning procedure in order to reduce cycle times,” explains Fabre. “This is one of our main concerns both today and in the future. These improvements include optimizing the algorithms for the positioning of aircraft parts to one another...”. Aircraft assembly based on laser measurements is a technologically mature process and can be carried over to other programs within our organization. After the measurement methods we developed are carried over to the military A400M project, they will most likely be used on the upcoming A350 program as well.”.