Improperly installed CF6-80C2 bearings have been linked to two incidents, including a January 2023 uncommanded engine failure on a new Boeing 767-300 freighter, prompting the FAA to mandate inspections for affected engines flagged by GE Aerospace.

An FAA airworthiness directive (AD) set for publication Oct. 4 flags about 40 engines by serial number that need inspections to ensure number 4R and 5R bearings are correctly installed. The check involves inspecting a magnetic chip detector that both bearings use. If a certain amount of metal particles is on the detector’s probe tip, affected engines must be removed.

GE recommended the checks in an Aug. 25 alert service bulletin. The FAA mandate, based on GE’s bulletin, calls for inspections within 15 cycles. It affects 37 engines on U.S.-registered aircraft, the FAA estimates. Affected operators are inspecting their engines, GE said. No additional findings have been reported.

The AD, adopted without draft and public-comment periods, does not provide many details on the January occurrence. But its description matches a Jan. 3 engine failure on a Maersk Air Cargo 767-300F operated by Amerijet International departing Seoul en route to Anchorage, Alaska. The engine failed soon after takeoff and the three-person crew safely returned to Seoul.

The second incident was a failed pre-delivery acceptance test in early August, the AD said.

“The presence of improperly installed number 4R or 5R bearings, discovered after the January ... 2023 engine fire and the Aug. 4, 2023, GE CF6-80C2 engine disassembly, could lead to bearing failure and consequent engine fire and damage to the airplane, which indicates an immediate safety of flight problem,” the AD said. A Korean Aviation and Railway Accident Investigation Board-led probe on the January occurrence determined “misalignment of the 5R bearing outer ring in the 5R bearing housing” triggered the failure. A final report on the event has not been made public.

Affected engines could be installed on Boeing 767s, Boeing 747-400s, and Kawasaki C-2s, the AD said. But the problem shows itself early in the engine’s service life, suggesting that recently delivered 767 freighters with GE engines are affected most. Boeing has delivered 48 since 2021—43 of them to either FedEx or UPS.

The AD specifies that checks are only required for engine serial nos. 630-136 through -56 and 707-510 through -645 for motors with fewer than 400 flight cycles since new.

The Maersk Air Cargo aircraft involved in the January incident had been in service for less than three months when its engine failed, the Aviation Week Network Fleet Discovery database shows.