What happened
On May 30, 2019, a China Airlines Airbus A330-303, registration B-18352, was operating a scheduled passenger flight from Hong Kong International Airport to Taiwan Taoyuan International Airport. The flight was carrying 243 passengers and 12 crew members.
During the climb phase, while passing through approximately 26,672 feet, the flight crew received an engine high vibration advisory for the number one engine. Shortly thereafter, the crew heard a loud bang and felt a physical shock, followed by an engine fire warning. The flight crew immediately executed emergency procedures, which included reducing thrust, shutting down the engine, and discharging the onboard fire extinguishers. The captain declared a Mayday and initiated an emergency return to Hong and Kong. The aircraft landed safely at Hong Kong International Airport at 09:31 UTC+8, with no injuries reported among the 255 persons onboard.
The investigation
The Taiwan Transportation Safety Board (TTSB) conducted the investigation, involving international agencies including the NTSB, BEA, and Airbus. The investigation focused on the mechanical failure of the number one engine and the maintenance history of the component parts. Investigators examined the engine's shop visit records, specifically looking at the recent performance restoration work performed on the engine.
Findings
Technical analysis revealed that the misassembly of a 4R stationary air/oil seal during the engine's last heavy repair was the primary cause of the incident. The seal was incorrectly seated, leading to an ovalized inner diameter. This reduced the clearance between the stationary and rotating seals, causing heavy rubbing and overheating during normal operation.
As the seals degraded, the oil sump cavities lost their ability to contain fluids. Debris from the damaged seals then impacted the 4R rotating vent seal. This allowed high-pressure, high-temperature compressor air to enter the sump cavities, triggering the auto-ignition of the oil. The resulting fire eventually burned through the low-pressure recoup tubes and sump vent tubes, spreading the fire through the engine compartment.
Contributing factors included the use of an alternative installation method that deviated from the latest manual revision and the lack of a required gage fixture at the time of maintenance. While the manufacturer, GE Aviation, had accepted the alternative method, the operator's work cards did not fully incorporate all recommended precautions, increasing the risk of procedural omission.