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Description of Driving Event:

The National Transonic Facility (NTF) is a transonic wind tunnel primarily intended to provide a high Reynolds Number test capability for aerodynamic research and the development testing of commercial and military aircraft configurations. On 1-18-89, the NTF experienced a Type A mishap, resulting in irreparable damage to all 25 fiberglass fan blades, significant damage to the upstream nacelle region and minor damage to tunnel internals downstream of the fan. The mishap was initiated by local failure (due to fatigue and fracture damage) of the External Thermal Barrier (ETB) retainer, resulting in high energy release of damage causing metallic parts.

The Mishap Investigation Board determined that one factor contributing to the mishap was the failure of the Safety Analysis Reporting System. The ETB was not treated as a critical assembly or as a critical item of the ntf drive system (i.e. It was not recognized as a single point failure which could result in a Type A mishap). There were no inspection or maintenance requirements developed for the ETB retainer. A Safety Analysis Report (SAR) was not performed by either the contractor or NASA.