Friday, December 1, 2006
Nacelle Maintenance Business
“Usually, nacelle maintenance is on condition and no overhaul is scheduled,” Philippe Catté, head of the customer support division, told Aviation Maintenance during a visit to Aircelle’s Le Havre, northwestern France facility in October. However, repairs are relatively frequent because of the nacelles’ exposure to damage. In flight, foreign object damage is not uncommon. On the ground, ramp trucks or technicians often cause dents or more serious problems.
In addition, engine events such as surge can prompt strong vibrations that de-bond composite materials. Some 60 to 70 percent of the nacelle’s weight is made of composites, Catté pointed out. The Safran group company claims to have 100 customers for its nacelles, including 20 customers with “big” numbers of nacelles.
Repair and maintenance currently account for 60-70 million ($75-88 million), or 11 percent of Aircelle’s revenues. The firm launched its repair business in 2002 and dubbed it Aircelle Europe Services. Before, Aircelle customers (airframe or engine manufacturers or other nacelle makers) were in charge of this activity, Catté explained. For example, Rolls-Royce was responsible for Trent engine nacelles on the Airbus A330. Embraer was supporting nacelles on its regional jets. Depending of their in-house skills, they would repair nacelles themselves or send them to Aircelle.
Inaugurated in 2004, the Pont-Audemer repair facility employs 60 people, including 30 percent of interim workers. It is located in Normandy, near the Le Havre factory. There is also a 24/7 warehouse in Paris CDG airport. “To up-start our service organization, we tapped people at sister companies in the Safran group, such as Snecma and Messier Services,” Catté told AM.
A cultural change has been necessary to get used to the requirements of a service business, he emphasized. Aircelle employees did have a know-how in repair jobs, but turnaround times were not real constraints. Now, engineers can be called on Sundays to study the feasibility of a repair job. If a repair is impractical on wing, Aircelle offers a nacelle swap and repairs the damaged one in house.
Similarly, a hotline has been set up. “We started being able to directly answer 20 percent of customer requests; we now stand at 50 percent,” Catté said.
In the U.S., Aircelle has a partnership with Continental feeder Expressjet, which wants to grow its service business, Catté explained. The Safran subsidiary supplies parts, while Expressjet technicians perform the repairs. “We are now looking for a partner for A380 nacelle support in the U.S.,” Catté said. There is also a 24/7 warehouse in Sterling, Virginia. As of early November, Aircelle was looking for another location.
In Asia, HAECO, Cathay Pacific’s sister company, is one partner. Singapore-based Gasca is the other. Gasca is a Goodrich-Singapore Airlines joint venture, Catté added.
As air transport in the United Arab Emirates is growing very fast, Aircelle is considering establishing a complete repair base there. It would be similar in size to the Pont-Audemer facility. Airbus A330s are numerous already in the region and dozens of A380s are poised to be operated there, too. However, because of the huge delays in A380 deliveries, Aircelle has postponed this plan. Instead, it is now creating a smaller repair station in Dubai, in Emirates’ hangars.
Field reps can be found in Brazil, South Africa, India, United Arab Emirates and several European countries.
Nacelle maintenance does include scheduled checks. But these checks are only made of check-lists and include no do-list, Catté explained. On the one hand, some customers do express the wish for a more structured maintenance. On the other hand, Aircelle would like to pull customers into by-the-hour agreements, which would obviously provide more predictability in revenues. Therefore, Aircelle salespeople are offering such contracts. They still have to have one inked, however. “Airlines, like aircraft manufacturers, see nacelles as simple products,” Catté said (see box). Hence their reluctance to pay expensive rates for a by-the-hour contract.
In recent years, design engineers have been made aware of some maintenance issues. The feedback they received has helped them design nacelles with improved maintainability. For example, some parts such as J-rings have been segmented which allows for partial replacement when it is partially damaged. Only the one segment needs to be replaced. Another issue has been to prevent, via proper designs, human error during maintenance. Currently in the design phase, the nacelle for the SaM146 regional jet engine may benefit from similar efforts. To ease maintenance, Aircelle is trying to make the nacelle removable without having to remove a layer of engine build-up components. However, the design is not completed yet; neither is the final tradeoff, Catté said.
The move from hydraulic to electric power for thrust reversers, as on the Airbus A380, is expected to bring simplicity. “Airlines will get rid of leaks, aging seals, and various issues linked to hydraulics,” Catté said. In return, the likeliness of problems coming from control software will increase.
Aircelle considers itself a major nacelle manufacturer but acknowledges smaller ones, such as Nordam, have a much more developed repair business. The French-based company considers its main competitors on the nacelle manufacturing market to be Goodrich and Spirit Aerosystems. The latter took over Boeing’s nacelle work after the U.S. aircraft manufacturer decided to spin off its nacelle activities.
The Safran subsidiary has 3,500 employees and produces engine nacelles for the Pratt & Whitney PW6000 on the A318, the Rolls-Royce Trent 500 on the A340-500/600, and both the Trent 900 and the Engine Alliance GP7200 on the Airbus A380. On regional jets, Aircelle supplies nacelles for the Embraer 170’s CF34-8 and the Sukhoi Superjet 100’s Snecma-NPO Saturn SaM 146. Aircelle is also a provider of nacelles for the PW307 on the Dassault Falcon 7X business jet.
On some airplanes, Aircelle does not manufacture the entire nacelle, just the thrust reverser. This is the case on the CFM56 on the Airbus A320 family. Other examples of Aircelle thrust reversers include business jet engines such as the Rolls-Royce BR710 on the Bombardier Global family and the Gulfstream 500 series, as well as the Honeywell HTF7000 on the Challenger 300. There also are Aircelle reversers on the Embraer 135 and 145 (Rolls-Royce AE3007 engines), the Trent 700 on the A330 and Rolls-Royce RB211s on the Boeing 747 and 767.
In its nacelle product line, Aircelle has a variety of thrust reverser technologies. One reason for this is that the company is the result of a three-way merger — Hurel-Dubois, Hispano-Suiza and Lucas Aerospace nacelle activities came together in recent years.
According to Lepage, the company is preparing to bid for nacelles on Boeing’s next generation narrow-body airplane.
Jewel Within a Jewel
Those who still think nacelles are hardly more complex than the hood of their car should reconsider. For example, internal temperatures can be as high as 600 degrees Celsius, while the outside air is as cold as minus 50 degrees. This extreme temperature variation requires exotic metal alloys or composites. Another role of the nacelle, noise reduction, calls for advanced materials, too.
In addition, movable cowling panels should swivel in very ample ways, in spite of up to 120-foot surfaces. But they should adjust very precisely when closing, without any gap or overlap. Otherwise this would cause turbulence and the aerodynamic performance would be affected.
Moreover, thrust reversers — a key part of the nacelle — have to redirect the engine’s thrust in the forward direction. These are tremendous efforts but this is not a reason for unleashing weight.
Nevertheless, in spite of the engineers’ endeavor, the nacelle is relatively heavy and represents 25-40 percent of the entire powerplant system’s weight. This depends on the size of the engine — the smaller the engine, the higher the relative weight of the nacelle.
As a result, nacelles on an Airbus or Boeing aircraft account for 20 percent of the entire powerplant system’s price. On a regional jet, this can be as much as 40 percent.