Summary
This document proposes to supersede an existing airworthiness directive (AD), applicable to certain Textron Lycoming reciprocating engines, that currently requires replacement of sintered iron impellers in oil pumps. This action would continue to require replacement of sintered iron impellers, but would also require replacement of aluminum impellers. This proposal is prompted by reports of additional oil pump failures caused by aluminum impellers, which do not have the reliability of the hardened steel impellers. The actions specified by the proposed AD are intended to prevent an oil pump failure due to impeller failure, which could result in an engine failure.