The and (EASA) are taking steps to remove certain repaired -5A low-pressure turbine nozzle guide vanes from service due to “dimensional anomalies” that could, under certain circumstances, lead to uncontained engine failures.
The issue, detailed in an FAA airworthiness information bulletin issued earlier this month, involves vanes repaired by Chromalloy. The repair process used “increases the dimensional variation in the features that provide the primary cooling air to the turbine,” the agency says.
The resulting overheating shortens useful lives of parts, which could lead to failures.
Chromalloy issued a service bulletin March 18, recommending that all affected vanes be replaced.
In its bulletin, the FAA says the issue is not enough of a hazard to warrant a mandatory fix with an airworthiness directive (AD). But EASA, which often adopts FAA’s bulletins as written, disagreed with this view, opting for a proposed AD that would mandate removal of affected guide vanes at the next shop visit or by Jan. 1, 2018.
EASA notes that the condition “could reduce turbine cooling and affect the service life of the affected parts, which includes critical parts, possibly resulting in release of uncontained high energy debris.”
EASA's proposed AD is open for comment through June 21.