The FAA plans to mandate a recently introduced fix for CFM International Leap 1A non-synchronous vibration (NSV) problems that has led to several in-service incidents.

In a draft airworthiness directive (AD) set for publication Oct. 11, the FAA proposes requiring operators to monitor NSV levels and replace the No. 3 bearing “spring finger housing” to prevent premature wear, the FAA said. Certain conditions would trigger a requirement to replace stage 2 high-pressure turbine nozzle assembly honeycomb and stator stationary seals.

The directive would give operators of affected Airbus A320neo-family aircraft 125 cycles to calculate NSV data and repeat the process every 125 cycles. If certain CFM-specified thresholds are exceeded, the bearing must be changed. In addition, it would mandate swapping the bearing out before the engine reaches 9,900 cycles.

CFM issued recommended instructions in a June 2023 service bulletin. Aviation Week reported in June that the fix was in the works. The FAA’s directive is based on the bulletin.

“This AD was prompted by a report of multiple aborted takeoffs and air turn-backs caused by high-pressure compressor (HPC) stall, which was induced by high levels of non-synchronous vibration,” the FAA said. “Additional manufacturer investigation revealed that wear on the No. 3 bearing spring finger housing can lead to high levels of NSV.”

The fix is one of several changes CFM is rolling out on the Leap family to address nagging issues. The most significant is a reverse bleed system that CFM expects to solve a long-running fuel nozzle coking issue.

It also plans to introduce a new Leap 1-series turbine blade in 2024 that will increase engine durability, particularly when operating in hot, dusty environments. The new blade will be incorporated into production engines and available for retrofits.