What happened
On May 11, 2006, a Korean Air Airbus A300-B4-622R, registration HL-7297, was operating a flight from Incheon International Airport, Republic of Korea, to Chiang Kai Shek International Airport, Taipei. The aircraft was carrying 128 occupants, including 117 passengers and 11 crew members.
While cruising at 32,000 feet approximately 30 nautical miles south of the SALMI waypoint, the flight crew received a cabin pressure regulator fault alert. This was quickly followed by a significant increase in cabin altitude, which rose past 9,000 feet and then 10,000 feet, with a vertical climb rate reaching 3,000 feet per minute. In response to the rapid decompression, the crew initiated an emergency descent according to the Quick Reference Handbook (QRH). During the descent, oxygen masks for 230 of the 267 passengers deployed automatically. The crew eventually stabilized the aircraft at 10,000 feet by resetting the cabin pressure control system and landed safely at Chiang Kai Shek International Airport. There were no injuries and no damage to the aircraft.
The investigation
The investigation, conducted by the Taiwan Transportation Safety Board (formerly ASC), involved representatives from the aircraft manufacturer, the state of operator, and various aviation authorities. The investigation focused on the mechanical failure of the cabin pressure control system and the crew's response to the depressurization event.
Findings
- A broken flange in the automatic mode motor drive component caused the forward outflow valve to fail, which subsequently prevented both automatic modes from controlling the valve.
- The flight crew did not transition to manual mode to maintain cabin pressure control during the event.
- There was a lack of integrated procedures to guide crews when both pressure regulators fail simultaneously with rapid decompression, specifically regarding whether to prioritize the regulator fault procedure or the emergency descent procedure.
- The flight crew did not follow standard procedures for initiating a turn during the emergency descent.
Safety action
- To Korean Air: Ensure flight crews follow specific emergency procedures and enhance operating proficiency; review and integrate emergency procedures related to loss of cabin pressure.
- To the Korean Ministry of Construction & Transportation: Monitor the implementation of safety recommendations provided to the airline.
- To Liebherr Aerospace: Conduct a detailed investigation into the damaged flange of the motor drive component.