What happened
On October 10, 2010, a Korean Air Boeing 747-400, operating as flight KE023 from Seoul to San Francisco, California, experienced an uncontained release of turbine material from its number 3 engine. The aircraft, registered as HL7489, was approximately 40 minutes into its flight when the crew noticed engine vibrations, oil pressure indications, and high exhaust gas temperature.
In response to these indications, the crew shut down the Pratt & Whitney PW4056 engine and initiated a return to Seoul. The aircraft landed without further incident, and there were no injuries reported among the passengers or crew.
The investigation
The investigation was conducted by the Korean Aviation & Railway Accident Investigation Board (ARAIB), with the NTSB providing a U.S. Accredited Representative. Post-landing examination of the No. 3 engine revealed that the exhaust sleeve was missing. Additionally, investigators found a large hole in the low pressure turbine case, which exposed extensive internal damage within the engine.