The US FAA has issued a new airworthiness directive (AD) requiring new inspections on the aging CF6-50 engines.
Operators are required to check core vibration levels, inspect the high pressure turbine rotor blade and exhaust gas temperatures and conduct a special inspection for the low pressure turbine rotor.
The latter's forward spacer arm on the stage 3 disk must be checked using a fluorescent penetrant inspection (FPI), according to the AD.
All findings showing cracks and disks and core vibration levels that fail inspections must be reported to the FAA.
The AD was issued because the FAA received reports of new high pressure turbine rotor imbalance, as well as two additional "disk events" on the low pressure turbine rotor stage 3, the agency says.
GE Aviation, the CF6-50 manufacturer, welcomed the AD as a "strong enforcement mechanism".
"It is imperative that today's CF6-50 operators remain as diligent with engine maintenance discipline and rigor as when these engines entered service 39 years ago," GE Aviation says.