Reliability seen as critical to success of greener engines

Airlines do not want to compromise reliability and low maintenance costs in the quest for lower emissions, according to CFM International GM-Marketing Bill Brown. Speaking at the Eco-Aviation Conference, he said CFM surveyed 400 operators over four years as it developed the Leap-X and ontime departures and a hold on maintenance costs were the key operator expectations. He said CFM operators now are enjoying 99.98% dispatch reliability from an engine that has 31 applications with 480 million flight hr. of experience.

The LEAP-X will deliver 15% lower fuel burn and thus CO2 and a 50% reduction in NOx and will be up to 15dB quieter than Stage 4 while offering the same reliability and maintenance cost as the current CFM56, Brown claimed. This has been achieved by incorporating much of the GE90 and GEnx technology into the new engine, he said. The 15% lower fuel burn will come from a 45% higher propulsive efficiency through increased bypass ratio and lower weight combined with 45% higher thermal efficiency and integrated engine systems, he said.

“LEAP-X technology will actually enter service in late 2010 on the GEnx engine,” Brown told attendees. The GEnx has the same composite blades, compressor, TAPS and aero technology as the LEAP-X. CFM built the first core for the LEAP-X last year and the second core is underway. Three cores will be completed by 2012 with a design freeze in 2011. The engine’s blades already have passed critical bird strike, blade-out and crosswind tests. Airbus and Boeing are expected to commit to re-engine/new aircraft decisions for the A320/737 upgrade/replacement later this year.

Pratt & Whitney VP-Technology and Environment Alan Epstein agreed that maintenance costs and reliability are critical, claiming that the PW1000G geared turbofan will have lower maintenance costs than the V2500 while the fan-drive system has shown “extraordinary reliability” in test. He said Pratt is forecasting “$1.5 million annual cost savings per aircraft” for the engine, “and we have demonstrated the equivalent of 40,000 takeoffs with no significant wear." He was upbeat on the longer-term performance gains for the GTF with a promise of a 30% reduction in fuel burn by the 2025-30 timeframe.

On the more holistic issue of future and radically different aircraft/engine configurations, Epstein thinks they may offer “dramatic gains” in fuel reduction, particularly in the shorter-range mission. “Significant gain comes from optimization for low flight speed [Mach .74],” he said. But because of the technical risks, he called for a NASA-funded "X-Plane" first to prove the concepts.