Action
Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.
Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Airmotive Engineering Corp. (AEC) replacement parts manufacturer approval (PMA) cylinder assemblies marketed by Engine Components International Division (ECi). These cylinder assemblies are used on all Continental Motors, Inc. (CMI) model 520 and 550 reciprocating engines, and on all other CMI engine models approved for the use of model 520 and 550 cylinder assemblies, such as the CMI model 470 when modified by supplemental type certificate (STC). The NPRM proposed to require initial and repetitive inspections, replacement of cracked cylinder assemblies, and replacement of cylinder assemblies at reduced times-in-service. The NPRM also proposed to prohibit the installation of affected cylinder assemblies into any engine. The NPRM was prompted by reports of multiple cylinder head-to-barrel separations and cracked and leaking aluminum cylinder heads. This supplemental NPRM (SNPRM) modifies the schedule for removal of the affected cylinder assemblies, adds that overhauled affected cylinder assemblies be removed within 80 hours, eliminates a reporting requirement, and removes the requirement for initial and repetitive inspections. We are proposing this SNPRM to prevent failure of the cylinder assemblies, which could lead to failure of the engine, in-flight shutdown, and loss of control of the airplane. We are reopening the comment period to allow the public the chance to comment on the proposed changes to the NPRM.