On January 19, 1994, a British Aerospace ATP (registration N857AW) operated by United Feeder Services was involved in an aviation accident near South Bend, IN. Investigators recorded the probable cause as: an internal failure of the auxiliary power unit. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
Auxiliary power unit auto shutdown; captain's restart failed. Crew notified of fire; fire bottle discharged; evacuation conducted. Post-incident inspection found turbine damage.
Incident Overview
The auxiliary power unit (APU) experienced an automatic shutdown during operations. The cockpit crew reported no indications of any anomaly with the APU prior to the shutdown. The captain subsequently attempted to restart the APU, but the effort was unsuccessful.
Fire Detection and Response
Following the failed restart attempt, the cockpit crew was informed that the APU was on fire. The captain activated the APU fire extinguisher system (fire bottle). The aircraft was evacuated without further incident.
Post-Inspection Findings
A detailed examination of the APU revealed a hole through the turbine nozzle vane platform. This defect resulted in thermal failure of the turbine wheel blades. No other contributing factors were identified during the inspection.