Key Points:

  • The Federal Aviation Administration (FAA) has released a proposed rule to necessitate inspections and component replacements in CFM International Leap-1A turbofans.

  • This decision comes after multiple reports of high-pressure compressor stalls, some of which led to aborted take-offs.

  • The proposed requirements are based on CFM's service bulletin issued in June, addressing the engine issue.

Close-up of a CFM International Leap-1A turbofan engine

Addressing Engine Concerns: FAA's Stance on Leap-1A Turbofans

In response to a series of high-pressure compressor stalls in CFM International Leap-1A turbofans, the FAA has put forward new maintenance requirements for these engines. These turbofans are primarily employed in powering Airbus A320neo-family aircraft.

Stall Incidents Propel Regulatory Action

The FAA's decision was triggered by multiple incidents, notably several aborted take-offs and in-flight turnbacks, which were attributed to high-pressure compressor stalls. The stalls stemmed from elevated levels of non-synchronous vibration, resulting in wear on the engines' number three "bearing spring finger housings."

CFM's Service Bulletin and Proposed Maintenance Measures

In June, CFM had released a service bulletin to address this particular issue. The FAA's recommendation necessitates operators to adhere to the provisions of this bulletin. Key procedures include repetitive vibration data calculations, to be undertaken at intervals no longer than 125 cycles. If discrepancies are identified during these calculations, airlines would be mandated to execute additional measures within the next 150 cycles. Such measures encompass the replacement of the bearing spring finger housings, coupled with a thorough inspection to detect potential “rubs” within the honeycomb structures located in stage two high-pressure turbine nozzles and corresponding stator stationary seals. The proposal further stipulates the replacement of any compromised honeycomb structures.

The Underlying Risk

Recent occurrences have recorded five instances of high-pressure compressor stalls with three leading to halted take-offs and the remaining two causing pilots to revert post-departure. The FAA emphasizes the gravity of this situation, noting, "Such conditions, if left unchecked, may lead to a loss of engine power during critical flight phases, such as the take-off or ascent." The proposal pertains to 48 Leap-1As operating within U.S. airlines' fleets. Based on the directive, airlines might find themselves replacing the number-three bearing spring finger housings in approximately 33 engines.