Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for (RRD) Dart 528, 529, 532, 535, 542, and 552 Series turboprop engines. That AD currently requires a dimensional inspection of the intermediate pressure turbine (IPT) disk or an ultrasonic inspection of the seal arm contact between the high pressure turbine (HPT) and the IPT disk seal arm and reworking or replacing the IPT disk if worn beyond acceptable limits. This proposed AD would continue to require those actions. This proposed AD results from us including an incorrect engine model and omitting an engine model from the applicability of the existing AD. We are proposing this AD to prevent HPT disk failure, which can result in an uncontained engine failure and damage to the airplane.