What happened
On June 23, 2009, a Korean Air Airbus A300B4-600R, registered HL7240, was operating a scheduled flight from Jeju International Airport to Chubu Centrair International Airport. While cruising at approximately 33,000 feet near Hikari City, Yamaguchi Prefecture, the aircraft encountered icing conditions, prompting the crew to activate the engine and wing anti-ice systems.
Shortly after activating the wing anti-ice, the flight crew observed a series of cascading failures on the ECAM, beginning with an engine bleed fault and progressing to failures in both air conditioning packs. As the cabin altitude rose rapidly, the pilot experienced symptoms of hypoxia, including dizziness and nausea, prompting the deployment of oxygen masks. The pilot declared a MAYDAY and initiated an emergency descent to 10,000 feet. The aircraft eventually landed safely at Chubu Centrair International Airport with no fatalities and no injuries to the 164 people on board, though one passenger sustained minor burns from an oxygen generator.
The investigation
The Japan Transport Safety Board (JTSB) conducted an investigation involving authorities from South Korea, France, and Canada. Investigators analyzed the digital flight data recorder (DFDR) and cockpit voice recorder (CVR), and performed inspections of the airframe and various aircraft components in both Japan and Canada. The investigation focused on the sequence of pneumatic system failures and the failure of the automatic emergency announcement system to activate during the depressurization event.
Findings
- The primary cause of the depressurization was the stoppage of both air conditioning systems.
- This stoppage was triggered by the closure of both engine bleed valves, resulting from a failure in the No. 1 fan air valve and a fault in the No. 2 pneumatic controller.
- A temporary disruption in electrical continuity, caused by poor soldering in a related circuit, prevented the automatic emergency cabin announcement from playing when the oxygen masks deployed.
- While the crew observed indicators suggesting the outflow valves were fully open, the investigation could not definitively confirm this, though it noted the valves did not respond to manual control attempts during the incident.