FAA Takes Action on Boeing 737 MAX Engine Issues: LEAP-1B Compressor Stalls Addressed

The decision to issue the AD was prompted by incidents of high-pressure compressor (HPC) stall resulting in multiple aborted takeoffs and air turn-backs (ATBs), caused by non-synchronous vibration (NSV).

CFM International, the manufacturer of the LEAP-1B engine and a joint venture between General Electric (GE) Aviation and Safran Aircraft Engines, conducted an investigation and identified wear on the No. 3 bearing spring finger housing as a cause of high NSV levels.

To comply with the directive, airlines operating Boeing 737 MAXs with specific versions of the LEAP-1B engine will be required to perform repetitive calculations of the oil filter delta pressure (OFDP) data. Depending on the calculation results, the No. 3 bearing spring finger housing may need to be replaced. The AD also prohibits the installation of engines with affected No. 3 bearing spring finger housing on aircraft already equipped with defective housing.

The FAA highlighted the potential risks, stating that failure to address this unsafe condition could result in engine power loss during critical flight phases, such as takeoff or climb, loss of thrust control, reduced aircraft controllability, and even the loss of the aircraft itself.

The directive will be effective from June 13, 2023, and requires the OFDP data calculations to be performed before an engine reaches 125 flight cycles (FC) since new. Subsequently, calculations must be conducted at intervals not exceeding 100 FCs from the last calculation until the affected No. 3 bearing spring finger housing accumulates 1,000 FCs since new. If the OFDP data exceeds limits during the calculations, operators must replace the No. 3 bearing spring finger housing within 25 FCs.

According to FAA estimates, eight engines currently installed on US-registered aircraft will be affected. The OFDP data calculation is projected to cost $85 per work hour, while the replacement of the No. 3 bearing spring finger housing is estimated to cost $64,590 for parts and at least $1,445 for labor per aircraft engine, totaling $66,035.

Four parties, including American Airlines, Lynx Air, an anonymous commentator, and the Air Line Pilots Association, International (ALPA), provided comments on the AD. ALPA and the anonymous commentator expressed agreement without any additional comments, while American Airlines and Lynx Air offered feedback.

Although Lynx Air holds an Air Operator’s Certificate (AOC) in Canada, both airlines raised concerns and made requests regarding the installation prohibition of engines with affected housing, revision of cost estimates, and CFM International’s monitoring and calculation of the OFDP data.

The FAA concluded that, apart from minor editorial changes and previously described modifications, the AD would be implemented as proposed in the NPRM (Notice of Proposed Rulemaking). The agency confirmed that none of the changes would increase the economic burden on any operator.