COLOGNE- The European Union Aviation Safety Agency (EASA) is addressing non-synchronous vibrations (NSV) occurring on CFM International LEAP 1-A engines installed on the Airbus A319neo, A320neo, and A321neo aircraft.
The regulator identified instances of non-synchronous engine vibrations on these engines, leading to the issuing of an airworthiness directive (AD).
EASA AD for A320neo Engines
EASA has determined that certain parts of the engines, specifically the number 3 bearing spring finger housing with a specific part number, were installed on specific engines defined by the CFM International Service Bulletin (SB) LEAP-1A-72-00-0504-01A-930A-D Issue 002.
The engine manufacturer issued its corrected SB in October 2023, and EASA subsequently issued its proposed AD on October 25, 2023.
However, the regulator cautioned that the affected parts on the LEAP-1A engines could experience accelerated wear, potentially leading to increased NSV. This condition could result in engine stalls or secondary air system seal rubs, reduced cooling airflow, or elevated temperatures in turbine internal cavities.
These issues could ultimately cause high-pressure turbine (HPT) disc failures. An HPT disc failure could release high-energy debris, posing a risk to the aircraft’s integrity and/or reducing its controllability.
Therefore, EASA has mandated the monitoring and assessment of NSV and, based on operators’ findings, requires the removal of the engine from commercial operations and replacing the affected number 3 bearing spring finger housing before it is returned to passenger service.
Last Date: May 6, 2024
However, the European regulator stated that operators must assess the NSV of their LEAP-1A engines within 125 flight cycles (FC) after the effective date of this AD, which is May 6, 2024. It’s important to note that a single flight cycle for an engine is counted when the aircraft takes off and arrives at an airport.
EASA has also required the inspection of the stage 2 HPT nozzle assembly honeycomb and HPT stator stationary seal honeycomb. Depending on the findings, airlines may need to replace either one or both of the honeycombs.
Following the initial inspection of the engines’ operations, airlines must assess NSV at intervals not exceeding 125 FCs.
Furthermore, unless operators have already replaced the affected part, at the next piece-part exposure or before the affected part exceeds 9,900 FCs since new, whichever occurs first after the effective date of the directive, carriers will have to replace any affected part, as identified in the CFM International SB with a specific serial number.
Not A Significant Impact
At the time, the FAA stated that CFM International reported at least three instances of aborted takeoffs and two air turn-backs, all due to HPC stalls. Nonetheless, the impact on US operators should be minimal.
In October 2023, the FAA estimated that its NPRM would affect 48 engines installed on aircraft in the US, with 33 engines in the US having parts that would need to be replaced as of the effective date of the regulator’s AD.
According to ch-aviation data, 162 active, in-maintenance, or stored Airbus A320neo family aircraft are equipped with the 13 LEAP-1A subtypes in the US. Eighty of those belong to American Airlines (AA), while the remaining are assigned to Frontier Airlines (F9).
Globally, Airbus has delivered 1,756 Airbus A320neo family aircraft with 13 LEAP-1A engine subtypes to operators. However, not every engine will be affected by either of the regulators’ directives since CFM International’s SB specifies specific serial numbers and part numbers of the number 3 bearing spring finger housing.
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