Summary
We propose to supersede an existing airworthiness directive (AD) that applies to certain Continental Motors, Inc. (CMI) IO-520, TSIO-520, and IO-550 series reciprocating engines, with certain replacement parts manufacturer approval (PMA) SAP investment cast cylinder assemblies installed. The existing AD currently requires initial and repetitive inspections and compression tests to detect cracks in those cylinders. Since we issued that AD, we became aware of additional engines that need to be added to the applicability. We are proposing this AD to prevent the separation of the cylinder head, damage to the engine, and damage to the airplane.