December 09, 2013
Technology being developed today for engine repairs or new production has a dual focus: lowering specific fuel consumption and increasing durability. OEMs spend considerable sums toward those ends.
“We are investing about $40 million, yearly in new repair development for engines that are currently in service, and we see that same level of investment continuing for the foreseeable future,” says Bill Moeller, director of aftermarket sales for Pratt & Whitney. “Over the past decade, we have spent in excess of $300 million on repair technology that will reduce fuel burn and extend material life.”
William J. Alibrandi, aero gas turbine analyst for Forecast International, a defense and aerospace consulting and production forecasting firm in Newtown, Conn., explains, “For at least the past six years, fuel has become the largest single cost of operating an airline, so anything that can be done to lower specific fuel consumption definitely impacts the bottom line. Any significant change in fuel cost savings is always engine-driven.”
Alibrandi cites the in-development CFM Leap. The OEM's approach is to increase the engine's thermal efficiency by increasing the compression ratios, resulting in higher exhaust gas temperatures. “That requires new materials in the form of ceramic matrix composites, which are installed in the hot section in the last stage of the high-pressure compressor. They provide increased heat resistance and save fuel,” he says.
“The engine OEMs are focusing on new technologies that increase engine temperatures to improve thermal efficiency, reduce overall engine weight, reduce fuel burn, maximize time on wing and improve maintenance costs,” says Richard Brown, London-based principal of international consulting firm ICF SH&E. “To achieve these objectives, the OEMs and their suppliers are investing in advanced materials and techniques including additive manufacturing, organic matrix composites, ceramic matrix composites, powdered metal and titanium-aluminide.”
At the same time, many of the high-tech repairs have focused on parts where the greatest savings can be made. “[They] tend to be on high-cost, high-value new parts such as HPT/LPT airfoils, LLPs, combustors and outer air seals,” Brown says. “Consequently, there are now very complex repairs available for engine blades and vanes and LLPs.”
In fact, for the Pratt & Whitney PW4000, a new Stage 3 vane bolt hole repair for the 94/100-in. models was introduced this year. According to the OEM, it restores the holes to OEM-acceptable limits, increases service life and extends time on-wing. The repair uses a proprietary process, which the company declined to discuss.