Paris Air Show

Nacelle tech keeps pace with engine advances

 - June 13, 2007, 11:12 AM

Manufacturers of nacelles and thrust reversers have no less interest in introducing new technology to their designs than do the suppliers of the engines inside them.

For France’s Aircelle, which claims European leadership in nacelle design and manufacturing, the arrival of the Airbus A380 four-engine airliner provided the opportunity to take another step in its path to an all-electric nacelle. The Safran subsidiary has already introduced electric functionality on several previous Airbus nacelles.

“Nacelles and thrust reversers are our core business,” Thierry Marin-Martinod, managing director of Aircelle’s System Centre of Excellence, told Aviation International News. “We have a solution that is very different from that of the competition, which reflects our expertise in all types of thrust reverser.”

Aircelle leads nacelle design on both the Engine Alliance GP7200 and Rolls-Royce Trent 900 engines powering the A380. “Our job is to anticipate requirements in terms of complexity, reliability and operability,” said Marin-Martinod. “This is the first time we’ve installed an electric system for the whole nacelle. It is one step further than the system on the A340-500/600, which is fitted with the first electrically operated fan cowl opening system in the world.” The A380 system comprises the electric thrust reverser, fan cowl door and cowl opening system, and being 100 percent electric, brings a number of advantages, including the elimination of a ground-support system.

The Hispano-Suiza-designed electrical thrust reverser actuation system (ETRAS) does away with hydraulics, since the entire drive train, including actuators, is controlled electrically. The ETRAS system was developed in partnership with Honeywell, which adds mechanical know-how to the electronics and digital systems designed by Hispano-Suiza, one of Aircelle’s founding partner companies.

According to Marin-Martinod, the all-electric A380 nacelle should bring a 35-percent reduction in maintenance time on the A380 because there is no need to replace hydraulic fluids, check joints and cure leaks. He added that low-temperature performance is better because there is no hydraulic fluid to thicken as temperatures decrease.

“The main specification for a thrust reverser is opening and closing time. Hydraulic systems begin to have performance issues at minus 15 degrees centigrade,”
explained Marin-Martinrod. “We have achieved an opening time of two seconds and closing time of three seconds at 30 degrees centigrade below zero, and we expect that kind of performance at minus 55 degrees. We just haven’t been able to find temperatures that low to test it yet.”

The next advance will come with what Aircelle calls its e-nacelle. “It is part of our continuous improvement strategy,” said Marin-Martinod. The design breaks away from mimicking traditional hydraulic systems, being far more integrated with the aircraft’s systems and saving more weight. It will also incorporate more functionality besides simple reverser deployment and stowing.

At this point, Marin-Martinod would say only that the design features many more electric functions inside the nacelle. “This third-generation electric nacelle benefits from our huge know-how in the development of electric nacelle technology at program level,” he added.

Goodrich Gets Lean
According to Goodrich’s aerostructures division president, Curtis Reusser, the U.S. company’s emphasis has been on leadership in lean manufacturing, cost and operational performance. Goodrich is the industry’s largest manufacturer of nacelles and has won an enviable position on all versions of the fast-selling Boeing 787 airliner, for both engine suppliers, as well as for the Airbus A350XWB (although General Electric has yet to propose a powerplant solution for the aircraft).

“We’re doing a lot of work with both engine suppliers,” said Reusser. “This is a big segment and we’re very pleased to be in such a strong position.” In his view, Goodrich has succeeded “because of our unique aerodynamic configurations, and on performance, acoustics and materials.”

Boeing did not choose an all-electric configuration, although Goodrich was involved in the design for the A380 and works with Aircelle in other areas. “I think Boeing wanted to make the best use of the electrical system on the 787 in terms of architecture and supply,” said Reusser.

“Our biggest push has been to listen more to the customer and to pull together all the available technologies,” he added. “We place a lot of emphasis on the manufacturing process in terms of automation, robotics and so on. We’ve also invested in a new plant in Mexico to reduce costs.”

Goodrich is making extensive use of composites in its nacelles, and Reusser said the emphasis is on using the latest automated fiber placement technology, which is new for nacelles, and lighter, higher temperature titanium alloys in the thrust reversers.

The company has recently announced that it is doubling the global footprint of its worldwide maintenance, repair and overhaul operations. “We’re in a very strong position here,” said Reusser. He added that about 60 percent of the work is on Goodrich nacelles and thrust reversers, the rest being for any other manufacturer.

Reusser also revealed that Goodrich may be looking to get back into the business jet nacelle business. It sold its former division in this market to Nordam some years ago.