FAA orders inspections of Lycoming piston engines over cracking pin defect

The Federal Aviation Administration has ordered urgent inspections of certain Lycoming O-235, O-540 and IO-540 piston engines after identifying a manufacturing defect that can cause piston pins to crack.

According to the agency, Lycoming reported metallic particles found in engine oil during routine changes, along with two engine failures that were not detected in advance. An investigation by the manufacturer traced the problem to thin-wall piston pins made with micro-cracks and material inclusions, a result of changes to honing and tooling processes at the pin supplier.

The affected pins were produced between January 2021 and December of an unspecified year, the FAA said, without giving the exact end date in the available material. Around 1,000 engines are believed to be affected, powering a range of small aircraft.

Under the final rule, which takes effect in 17 days, some operators must carry out oil changes and inspections before their next flight, while others have a five-hour service window to comply. The order also requires inspection of oil filters, screening for metallic debris, and replacement of the suspect piston pins.

The FAA said it bypassed its usual practice of collecting public comment before issuing the rule, citing the unsafe condition posed by the defect, and will instead accept comments after the fact.

Lycoming had already flagged the issue in a service bulletin issued in March, listing affected engines and instructing operators on pin replacement and inspection procedures. A further service document in April set out overhaul intervals. Lycoming did not immediately comment on the FAA's order.