Common Themes

Organizational Lapses

The engine manufacturer did not provide guidance to manufacturing personnel on how to determine the significance of manufacturing escapes. Quality control personnel identified a manufacturing error that had been made in approximately 100 oil feed stub pipes after the non-conforming parts had been installed on engines in service. However, there were no adequate processes provided to determine or establish the significance of the manufacturing error. An analysis determined that the incorrectly manufactured parts were adequate for installation. Once entering service, one of the incorrectly manufactured parts failed on the accident flight, leading to an uncontained engine failure.

Flawed Assumptions

A fundamental design assumption was that in the event of an IP turbine drive arm failure, the IP turbine assembly would translate aft and contact stationary structure, mitigating the potential for an IP turbine overspeed event. In this accident, the IP turbine continued to accelerate after failure of the drive arm, resulting in failure of the IP turbine disc.

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