“The FAA is concerned that the corrective action contained within AD 2020-16-11” regarding "fractured cross-flow cylinder assemblies" on certain Continental engines “is not sufficiently resolving the issue.” The agency published an airworthiness concern sheet October 25 seeking “additional input from the field in order to better understand whether any additional actions are necessary at this time.”
The 2020 AD was "prompted by reports of in-flight engine failures due to fractured cross-flow cylinder assemblies." The AD required “cylinder head inspection and removal of the casting material build-up on the radius edge of identified cross-flow cylinder heads to reduce the potential for fracture initiation.”
See the airworthiness concern sheet for the detailed information the FAA seeks. The FAA requests responses within 30 days.