All new-production CFM International Leap-1A and Leap-1B engines delivered to Airbus and Boeing as of last month incorporate a permanent fix to mitigate degradation of an environmental barrier coating in the ceramic matrix composite (CMC) shroud that surrounds the first high-pressure turbine stage, according to Gaël Méheust, president and CEO of the CFM joint venture.
Stressing that the problem never represented a safety issue, Méheust told AIN that, nonetheless, it has adversely affected the time on wing many in-service engines have managed to achieve. Loss of the coating reduces the amount of exhaust gas temperature (EGT) margin available to Leap engines, affecting their performance levels at high thrust settings and requiring operators to send engines prematurely for performance-restoration maintenance shop visits after only a few thousand hours’ time on-wing.
Méheust said the coating degradation problem manifested itself after “several thousand hours” in service. However, while by late June operators had sent “approximately 70” engines to CFM and its MRO partners for premature performance-restoration work, all engines removed by that date had been Leap-1As installed on Airbus A320neo-family aircraft, he confirmed. The Leap-powered A320neo entered commercial service in August 2016, on an aircraft operated by Turkish carrier Pegasus Airlines, some nine months before the first Leap-1B-powered Boeing 737 Max entered service with Malaysian carrier Malindo Air.
Once CFM became aware of the problem, it acted quickly to provide a temporary fix, according to Méheust. The solution relied on the fact that the designs of the two Leap models allowed extra EGT margin, a capability about which CFM knew from testing but hadn’t yet made available to operators. So CFM engineers managed to restore 25 degrees of EGT margin through a service bulletin, which instructed Leap operators to implement a Fadec software upgrade that immediately provided them with some additional time-on-wing flexibility.
“This is very important because it gives us the time to organize the return of engines to the shop,” said Méheust. The resulting additional time-on-wing flexibility allowed CFM and operators to organize Leap removals and replacements without any aircraft on ground emergencies occurring.
“We don’t want any and we haven’t had any,” said Méheust. “We have special teams that do nothing but deal with the airlines and monitor their engine performance.” In addition, “We are doing quick turn times to get these engines back” into service rapidly.
With the temporary fix in place, CFM developed a permanent fix for the coating-degradation problem by changing the bonding material it had used to adhere the environmental barrier coating to the surface of the CMC shroud segments.