All-electric brakes set for Boeing 787 by year-end
Messier-Bugatti (Hall 4 Stand B12) is scheduled to deliver the first complete braking system for the Boeing 787-8 airliner by December. The first all-electric brakes on a civil aircraft promises a weight savings and improved performance as well as maintenance ease and added safety. To support 787 production, the French company has established a workshop in Seattle within close proximity to the big airframer.
Boeing is planning to complete its own product validation during the third quarter of this year, François Tarel, director of the wheels and brakes division, told Aviation International News. Integration is already under way with Smiths Aerospace (Chalet P1-5) supplying the common core system and Crane Hydro-Aire (Hall 4 Stand G20) the antiskid system.
Boeing selected Safran subsidiary Messier-Bugatti as a brake supplier in November 2004, and since then the company has fast-tracked development of the braking system. The European design engineers worked under the 787’s global collaborative environment (a concurrent engineering network), as did every program partner. Messier-Bugatti simulated more than 1,000 braking operations on a test rig even before Boeing made its choice.
A control unit drives the electric braking system and is linked to motors that convert electric power to drive gear wheels, which in turn drive a ball screw and nut. The screw is linked to a piston that presses the carbon disks together. The piston is no longer hydraulic.
“At the aircraft level, replacing hydraulic systems with a more electric architecture saves weight,” Tarel said. He pointed out that there is another benefit at the assembly stage because it is easier for technicians to handle and connect wires than hydraulic pipes.
Maintenance technicians stand to benefit from the use of electric brakes, too, since electricity eliminates the risk of leaks and potential associated fire. Moreover, the techs can more quickly diagnose a failure because it is easier to find a failed component than to locate a leak.
Because control of an electric system can be fine-tuned, system response is faster, Tarel said. From the pilot’s point of view, this translates into slightly shorter braking distances. From the operator’s perspective, it translates into reduced maintenance costs because there is less wear.
Tarel said the company also has overcome electromagnetic compatibility issues and that all components have passed the required tests. Safran sister company Sagem participated in development of the control unit.
Generally speaking, system redundancies ensure reliability. “If one of the four control units fails, the three remaining can still supply 100 percent of the braking function,” Tarel explained. The company claims reliability is “at least as good” as that of an hydraulic system.
The Boeing 787 is to make its first flight during the third quarter of 2007, equipped with eight brakes–one on each wheel of the main landing gear. Airlines flying the 787 can choose between electric braking systems offered by Messier-Bugatti and Goodrich. No customer has yet made its selection. (Airbus is planning to evaluate Messier-Bugatti’s electric brakes on an A340-600 later this year, testing them only on the central main undercarriage.)