On February 19, 1990, a Short Brothers SD3-60 (registration N361MQ) was involved in an aviation accident near Chicago, IL. Investigators recorded the probable cause as: Fatigue failure of a turbine blade in the first stage power turbine. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A commercial aircraft experienced an engine failure due to a fatigue fracture in the power turbine blade while on final approach to Chicago O'Hare International Airport.
What happened
The aircraft was established on final approach for landing at O'Hare International Airport. As the aircraft crossed the landing threshold, the pilot reported hearing a series of small popping sounds followed by a loud pop originating from the number one engine. Immediately following these acoustic events, the pilot observed a significant decay in engine torque. The crew proceeded to feather the affected engine just as the aircraft touched down on the runway.
The investigation
Post-accident examination of the powerplant revealed the root cause of the sudden performance loss. Technical analysis identified a fatigue failure within the first stage of the power turbine. Specifically, a single turbine blade had fractured due to material fatigue, leading to the immediate mechanical failure reported by the flight crew during the critical landing phase.
Findings
The investigation concluded that the incident was caused by a structural failure rather than operational error or external factors. The primary finding was the fatigue failure of a turbine blade in the first stage power turbine. This component failure resulted in the sudden loss of power and the subsequent need to feather the engine during the final moments of the flight.
Probable cause
Fatigue failure of a turbine blade in the first stage power turbine.