Airworthiness Directives; Allison 250 Series Turbine Engines

This amendment adopts a new airworthiness directive (AD) that is applicable to Allison 250 series turbine engines. This action requires initial and repetitive visual inspections of all engine filters for metal particles resulting from premature wear of two bearings produced under Parts Manufacture Approval (PMA) by Superior Air Parts, Inc. In addition, this AD requires replacement of those bearings with bearings that incorporate improved retainers, which constitutes terminating action to the inspection requirements of this AD. This amendment is prompted by a report of a failure during a ground test of an engine with bearings manufactured by Superior Air Parts, Inc. The actions specified in this AD are intended to prevent bearing failure due to bearing separator instability, which can result in subsequent turbine and engine failure.