Created Wednesday, Dec 1st 2021 17:07Z, last updated Wednesday, Dec 1st 2021 17:07Z
A China Airlines Airbus A330-300, registration B-18352 performing flight
CI-922 from Hong Kong (China) to Taipei (Taiwan) with 243 people on board, was climbing through FL270 when the crew needed to shut the left hand engine (CF6) down. The aircraft descended to 11,000 feet, burned off fuel and landed safely back on Hong Kong's runway 07L about 90 minutes after departure.
The flight was cancelled.
Passengers reported a loud boom occurred when the engine failed. They were subsequently rebooked onto another flight.
The occurrence aircraft is still on the ground in Hong Kong about 69 hours after landing.
On Jun 4th 2019 Taiwan's ASC reported they opened an investigation into the occurrence and established an investigation commission. While climbing through FL250 out of Hong Kong the left hand engine experienced vibrations followed by ENG1 OIL QTY LOW and ENG1 FIRE indications. The crew shut the engine down, discharged the fire extinguisher, decided to return to Hong Kong and declared Mayday.
On Dec 1st 2021 Taiwan's ASC released their final report in Chinese only (Editorial note: to serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a Chinese only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).
The report concludes the probable causes of the occurrence were:
- the incident engine #1 experienced high vibrations and fire alarm during the climb. The 4R stator gas/oil seal had been installed inaccurately during a maintenance shop visit. The gap of the oil seal was too small, the stator and rotor oil/gas seals experienced too high friction during operation resulting in high temperatures which exceeded the design limits. The material strength of the seals was reduced, the centrifugal forces by the high rotation deformed the seal rack of 4R and bent it outwards further increasing the friction between stator and rotor. The severe friction and high temperatures caused severe damage to both stator and rotor and caused the seal of the lubricating oil chamber to fail.
- Broken fragments of the damaged 4R stator/rotor gas/oil seals hit the 4R rotor exhaust shaft seal causing serious damage to the shaft seal. HPRC high temperature/high pressure gas entered entered the lubricating oil chamber causing the oil chamber to catch fire, which burned through the LPRC causing leaks through the opening, so that the engine compartment became hot and triggered a fire alarm.
Findings related to the risk:
- For the installation and assembly of the 4R stator/rotor oil seal, if special gauges are not used to conduct the interference test between stator and rotors 4R, it may not be possible to ensure an adequante gap between rotor and stator
- in this case the procedure deviated from the then valid version in the manual. Although GE had accepted an alternate procedure by China Airlines the assembly work order did not match the laid out alternate procedure, too, which increased the risk of missing steps during the on-site assembly process. And it failed to maintain the integrity of the assembly documentation.
- the special guage fixture is very important for the correct positioning and inspection of the 4R stator/rotor gas/oil seal. China Airlines did take a long time to obtain such a special gauge fixture, which is not conducive to the maintenance personnel with respect to the current manual.
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