According to Ed Duran, GE Aviation's general manager for customer service engineering, the research and development for the GEnx—used on the Boeing 787 and 747-8—focused heavily on composites. “We use polymer composites in the GE90 fan blades, but for the GEnx we took that a step further by using composites in the fan case, which has resulted in a considerable weight savings,” he explains.
Duran also notes that the GEnx TAPS design enables the engine to exceed nitrogen oxide emission standards, thanks to a lean-burn approach that still maintains the combustor's durability requirements. The lean-burn process, he notes, was achieved using new manufacturing methods in the fuel-injector components.
The Leap family, he says, will benefit not only from the advanced parts technology derived from the GEnx and the GE90, but also from the CFM56 family, which was used as the design baseline. One example he cites is the Leap's high-pressure turbine blades that have been designed to run at the same metal temperature as those on the CFM56-5B. “They will have the same durability, even though the Leap will achieve 15% better fuel consumption.”
In tandem with durability, GE paid particular attention to component repairs. “During the design phase, there was a requirement for components—the combustor, the frames, the cases and the turbine and compressor airfoils—to be repairable. We think that those components will be more repairable, more of the time, as a result of the design requirements,” he states.
Users of the Leap engine will benefit from the electronic-trending technology incorporated into the GEnx, says Duran. “The GEnx diagnostics have the capability to provide more information on more systems in the engine because of better interrogation of events, which provides earlier warnings of potential issues. We will be extending that technology to the Leap family.”
Developments in trend monitoring have, in fact, resulted in an increasing amount of inflow data, revealing how an engine is operating in the field, reports Jacques Juneau, vice president of engine services for Abu Dhabi Aircraft Technologies (ADAT) in the United Arab Emirates. “Electronic data-generation capability has increased to the point where the information provided can determine the optimal time for engine removal without disrupting an airline's operations. Now we can determine the reason for an event, in less time, and know better where to troubleshoot, minimizing repair costs and those pertaining to spare engine fleet maintenance,” he says.
John McKirdy, vice president and global account executive for Chromalloy, notes that the new engines also are being designed for greater durability and repairability.
“That will mean more acceptance by the airlines of DER [designated engineering representative] repairs, since it's less costly to repair a part than to replace it. With industry requirements for greater on-wing life, increased fuel efficiency, decreased emissions and decreased maintenance costs, that often means developing parts that are less prone to deterioration under higher heat conditions, but at the same time, present more salvage or repair opportunities,” says McKirdy. “At Chromalloy, we have looked at parts considered to be non-repairable by the existing repair manuals and developed repair schemes we can certify for those parts,” he says.
The development of emerging nanotechnology coatings, which provide an enhanced thermal barrier, is helping to extend on-wing component life, says Juneau. “We see significant progress made in the coatings world. This should lead to longer on-wing time, although it is still too early to know for sure.”
Airlines appear to be taking somewhat of a wait-and-see attitude with respect to the new engine technology, especially where performance and life-cycle support agreements are concerned.