Published Final Report of China Airlines Flight CI922 Occurrence Investigation
The Taiwan Transportation Safety Board (TTSB) published the Final Report on the investigation of China Airlines Flight CI922, No.1 engine fire during the climb at 88 nm east-southeast (ESE) from Hong Kong International Airport(VHHH).
On May 30th, 2019, China Airlines scheduled passenger flight CI922, an Airbus A330-302, registration number B-18352, took off from Hong Kong International Airport (VHHH) to Taiwan Taoyuan International Airport (RCTP) at 08:36 (UTC+8) with 2 flight crew members, 10 cabin crew members, 243 passengers, a total of 255 persons onboard. During climb, around 88 nm ESE from VHHH and as passing through 26,672 feet, the aircraft experienced an in-flight left (no.1) engine fire. The flight crew responded by performing the abnormal procedures declaring an emergency, and initiating a turn back toward VHHH. At 09:31, the aircraft safely landed on runway 07L at VHHH airport without further incident.
According to the Transportation Occurrence Investigation Act of the Republic of China (ROC), and the content of Annex 13 to the Convention on International Civil Aviation, the Taiwan Transportation Safety Board (TTSB), an independent transportation occurrence investigation agency, was responsible for conducting the investigation. The investigation team also included members from US National Transportation Safety Board (NTSB), France Bureau d'Enquêtes et d'Analyses (BEA), AIRBUS, GE Aviation, China Airlines and Taiwan Civil Aeronautics Administration (CAA).
Findings related to probable causes:
- The no.1 engine of occurrence aircraft experienced high vibration and fire during climb. The root cause was determined to be 4R stationary air/oil seal mis-assembly during the last shop visit for a performance restoration (heavy repair). The incorrectly seated 4R stationary air/oil seal caused ovalization of the seal inner diameter which reduced the clearance between 4R stationary and rotating air/oil seal. During normal operation, it initiated heavy rubs and generated overheat between the 4R rotating and stationary air/oil seals. The 4R rotating air/oil seal deformed radially outward from overheating and centrifugal forces which caused further deep rubs on stationary seals. Eventually both seals were severely damaged and the oil sump cavities lost sealing capability.
- The liberated debris from damaged 4R rotating and stationary seals impacted the 4R rotating vent seal. After losing the separation of the vent seal, the high pressure and high temperature HP recoup air entered sump cavities and caused the oil auto-ignition fire. The fire entered and burned through LP recoup tubes and B/C sump vent tubes which caused the engine compartment overheat and fire.
Findings related to the risk:
- The installation of 4R stationary air/oil seal without using the gage fixture as prescribed in the latest engine manual revision would compromise the allowable clearance between 4R stationary and rotating air/oil seal.
- The alternative method of 4R stationary air/oil seal installation of the occurrence engine was deviated from the effective manual revision; however, it was accepted by GE Aviation. The work card prepared by the operator did not fully reflect the document and procedure recommended by GE Aviation. This might increase the risk of procedures omission and fail to retain the complete work records.
- The gage fixture is crucial to check the seal seating during 4R stationary air/oil seal installation. The operator did not acquire the tool in a timely manner, which is not conducive to maintenance personnel to perform the job in accordance with the latest revision of manual.
Safety Actions Taken:
During the investigation TTSB noted that the GE Aviation, China Airlines and CAA Taiwan have taken proactive safety actions, as follows:
Civil Aeronautics Administrative, Taiwan
- CAA has required and supervised China Airlines Engineering and Maintenance Department to revise the "Procedure of Engineering Order / EO Work Card Establishment” (QP08ME099) on April 21st, 2021, and implement it accordingly. The New revision added a requirement that when an alternative procedure (deviation from the latest manual) is accepted/received from the manufacturer, China Airlines shall issue a supplemental work card (Ad-Hoc Task) as a basis for work execution and documentation.
- CAA also has required and supervised China Airlines Engine Shop to revise the "Procedure of Engine Shop Technical Documents (Maintenance Manuals and Technical Bulletins) Revision and Control" (QP07MH008) on February 2nd, 2021, and implement it accordingly. The new revision prescribes that when an up-to-date maintenance manual requires new tools or equipment, a list of new tools and equipment must be made. The list must be reviewed in the routine Department Meeting until the acquisition of new tools/equipment is completed. The items of reviewing include purchasing, renting, and relevant efficiency assessments.
- Before obtaining the special tool, 2C18118G01, China Airlines performed the CRF No. 4R Stationary Air / Oil Seal installation adhere to GE SR #00737753 and followed the good shop practices.
- In the second half of 2019, China Airlines had rented the gage fixture, 2C18118G01, and performed CRF assembly according to the latest engine manual. The training and reminder were made to the maintenance personnel about the CAUTION notes described in the relevant engine manual and work cards to ensure that the installation of 4R stationary air/oil seal meets the requirements of the engine manual.
- China Airlines ordered the G02 tool in 2020/Oct and received it in 2021/Feb. China Airlines engine shop had completed the CRF assembly at least three E1 engines since the revision of the work cards on October 6th, 2020. The procedures have all met the requirements of the engine manual and work cards, and no assembly abnormalities have been found.
- Revised the Engine Shop Manual (ESM) for both the CF6-80C2 & -80E1 sections 72-34-00 to clearly identify the new 2C18118G01 tool must be used.
- Field communications to re-enforce the requirement to use tool 2C18118G01 includes Fleet Highlites article(s) and the Regional conferences and / or Working Together Teams (WTT’s) calls.
Transportation Safety recommendation
Arising from the conclusions of the investigation, the following safety recommendations are issued to relevant organizations.
To China Airlines
- Enhance the integrity of the engine installation work cards. If it is necessary to deviate from the latest engine manual revision, in addition to using the alternative method accepted by the engine manufacturer, the documents and procedures described in the alternative method shall be reflected on the work cards to reduce the risk of procedures omission and to completely document the results of work cards.
- Review and evaluate the acquisition process and schedule control of the special tools required for engine maintenance, and obtain the special tools needed in a timely manner to avoid the use of alternative solutions to reduce risk.
- Review and evaluate the assembly work order of the engine shop.to designate the items as maintenance significant items for the work which is similar to the installation of the 4R stationary air/oil seal, if it is not completed properly and its failure could endanger the safe operation of the aircraft.
To Civil Aeronautics Administration, Taiwan
- Supervise China Airlines engine shop performs engine installation/repair encountering the situation with necessities of deviation from the latest manual revision for a reason, the alternative method accepted or provided by the engine manufacturer must be used, and the documents/procedures described in the alternative method must be fully reflected on the work order. And supervise China Airlines to review/evaluate the acquisition process and scheduling control of special tools required for engine shop maintenance. Also require China Airlines to review and evaluate the engine assembly work order of the engine shop.to designate the items as maintenance significant items for the work which is similar to the installation of the 4R stationary air/oil seal of this occurrence, if it is not performed correctly and its failure could endanger the safe operation of the aircraft.
(Detailed information please refer to full Final Report)
Full Final Report in Chinese is available for download at https://www.ttsb.gov.tw
Vivi Yang, Executive Officer