SCHOOL OF MECHANICAL AND AERONAUTICAL ENGINEERING
ME3808 Human Factors
Accident Investigation Using MEDA
We declare that this submission does not contain plagiarized content.
Prepared and Signed By:
Marie Ng Mun Ling (P1747856)
Tan Sin Long (P1747799)
Goh Jun Wei Brandon (P1743076)
Muhammad Nur Fadhli (P1718450)
2. Chain of events
3. Contributing Factors
4. Company Policy (Evaluate companies policies and procedures were effective in preventing such error)
5. Recommendation (New Layers of defense as espoused by Reasons Swiss Cheese Model)
China Airlines Flight 611, a Boeing 747-209B with a registration of B-18255 was a scheduled international passenger flight from Taiwan Taoyuan International Airport to Hong Kong International Airport, on 25 May 2002. It was also its final service for China Airlines before it was bargained to Orient Thai Airlines. The reports suggest that the weather conditions were fine, and the local temperature was 28 degrees Celsius with wind speeds reaching 9 knots. At 2:48 local time, it was placed into position and cleared for take-off. 13 minutes later, the aircraft were not to be found on the radar screen as the plane was approaching 35,000 feet
The aircraft was reported to be disintegrated in midair as wreckage and bodies were found at sea, about 45km near the Penghu Islands. All 225 people on board which consist of 16 crew members, 2 pilots, one flight engineer, and 206 passengers were killed. Pieces of the aircraft were also found near Changhua. An immediate search and rescue operation were initiated. Among the 225 people, 175 bodies were found, and 75 percent of the wreckage was salvageable. No signs of foul play were found.
Fig 1.1 China Airlines
Fig 1.2 Route Taken642938169543
2. Chain of events
On February 7, 1980, the aircraft was involved in a tail strike during landing that damaged the skin of the aft lower fuselage. After the tail strike, inspection was conducted in Hong Kong, results show that abrasion damage was found on the fuselage, located at the bottom part of the aft portion between STA 2080 and STA 2160 and also between STA 2578 and STA 2658. China Airlines carried out two separate repairs, a temporary repair and a permanent repair. The temporary repair was done days after the tail strike while the permanent repair was then carried out from May 23, 1980 to May 25 1980. The repair was done by a team from China Airlines but then, it was not carried out in accordance with Boeings Structural Repair Manual (SRM) which resulted in metal fatigue in the aircraft.
According to Boeings SRM, the repair doubler must be installed in the aft lower fuselage to cover the scratches that resulted from the tail strike. The damaged area must be cut out before the application of the repair doubler or it should have been replaced to restore the structural strength to maintain the airworthiness of the aircraft. In the event that the scratches are too deep to be repaired, the entire damaged section has to be cut out and replaced with a repair doubler that was 30 percent larger than the removal area.
The maintenance technician carried out the repair by leaving the damaged skin in Section 46 and sanded down the scratches before the installation of the repair doubler. They did not cut out the damaged area even though the scratches were too deep to be repaired, as the damaged section was too large to be cut down. Hence a repair doubler was placed underneath the scratched area to cover the scratched area but it did not cover the whole damaged area.
Fig 2.1 and 2.2 Installation of repair doubler at Section 46
The purpose of the fasteners is to connect the joints of the structures and also the pressurized and unpressurized applications to transfer the load to one part to another part. The fasteners will aid in the prevention of propagation of any existing new and fatigue cracks if the damaged section are completely covered with the doubler plate. The repair doubler failed to completely and effectively cover the damaged section that there had scratches existed at the outermost of the fasteners that was securing the repair doubler. This resulted in no safe keeping against the propagation of any concealed cracks on the damaged skin in Section 46. After repetitive cycles of pressurized and unpressurized, cracks began to form around the scratches that was not covered by the repair doubler. Eventually, the cracks propagated and reached the breaking point that led to the complete disintegration of the aircraft.
Fig 2.30: Results of repetitive cycles of pressurized and unpressurized.
A further analysis of the structural stress and residual stress was conducted to assess whether the preexisting crack will have any effect on the integrity of the fuselage. The study was used to determine the critical damage length. The upper curve on fig 2.1 shows the capability of the damage skin without any multiple site damage while the lower curve represents the capability with the doubler installed. Thus, based on fig 2.2, if the crack length is 58 inches and longer even the application of normal loads acting on the aircraft will affect the residual strength of the fuselage. Despite investigators uncertainty in finding the exact length of the crack before the accident, further studies conducted on the hoop-wise fretting marks found on the doubler, the equally spaced marks and deformed cladding found, investigators concluded that the crack was 71 inches in length, far beyond the limits of 58 inches that was analysed, making it more than enough to significantly affect the fuselages residual strength. Meaning that the simplest of stress acting on the fuselage will cause the fuselage to break apart.
Fig 2.40: Residual strength with doubler
Furthermore, reports suggested that the cause of the metal fatigue was due to inadequate maintenance by the maintenance technician from China Airlines, but brown nicotine stains were found around the doubler plate by the investigators. Investigations suggest that the smoke was driven out from the cracks that resulted in the nicotine stains on the skin of the aircraft. These stains were caused by the smoke from the passengers cigarettes that was eventually banned seven years before the catastrophic accident. During the pressurization of the aircraft as the plane was flying, the nicotine seeped out and stained the part around the repair doubler. However, there were no strong evidence that shows that the nicotine stains contributed to the metal fatigue, but they could be related to simple applications such as loose rivet or fluids from other sources to stick in the area due to the airflow.
center000 Fig 2.50 : Brown Nicotine Stains were found
In 1988, the Aloha Airlines Flight 243s roof was peeled off while cruising at high altitude. Hence, FAA ordered that all airlines should evaluate the previous repair that was done earlier on the planes. In 2001, China Airlines started evaluating all the repairs and photographs 31 different doublers on different 747s were taken for documentation purposes. During the evaluation, there are stains found on the doubler that was caused by the passengers but none of this were reported. This catastrophic accident can be avoided if China Airlines reported and investigated the root cause of the nicotine stains that will result in a more detailed inspection which then could be carried out on the aircraft.
3. Contributing Factors
After thorough investigation using both the MEDA Form and the Aviation Occurrence Report, 3 main events were identified as the main causes on why the accident happen, below are the 3 main events with their contributing factors that led to the event which in turn led to the fatal accident.
3.1 Required Servicing not performed
One of the main contributing factors on why the required servicing was not performed was that there was no information on the servicing of an aged aircraft, the sentence Furthermore, because there were only a few aircraft that would fall into the aging aircraft category in Taiwan, the CAA did not take any action to adopt the program into the system immediately” (Aviation Occurrence Report ,2002, p.169). This suggests that there was no information being given to the operators and maintenance personnel on how to service the aged aircraft as the CAA was not prepared for the situation to happen.
Another reason on why the servicing was not performed was that the task became more difficult. This is evident in the phrase its very difficult to trace the QC procedures since the old QC procedures were discarded after revision (Aviation Occurrence Report ,2002, p.93. This means that every other servicing will become new and difficult as old procedures and manuals were replaced leaving behind a new procedure with a different method and manual.
Another reason on why the required servicing was not performed was that the planning and organization of task was not properly handled. This is supported by the sentence AMP CPCP item 53-125-01 inspection of the bilge was delayed in implementation for 13 months until the 1998 MPV check. The AMP required this item to be inspected every 4 years.” (Aviation Occurrence Report ,2002, p.25). This suggests strongly that the delayed inspection meant that the aircraft was flying in an unairworthy condition as the required servicing was supposed to be a year ago this is why the required servicing was not performed.
Lastly, the communications between the departments was a major factor on why the servicing was not performed. This is evident in the sentence no further communication between the System Engineering Department and MOC with respect to B747-200 CPCP scheduling issues, and no other department within CAL EMD monitored the implementation yield rate of the CPCP items” (Aviation Occurrence Report ,2002, p.17). This means that without communication between these respective departments, the servicing was left ignored and possibly pushed around as no one was willing to be responsible on the issues faced
3.2 Incorrect Structural Repair
Another reason for the fatal event was the incorrect structural repair that happened in 1980. The main contributing factor was that the information was not in used by the operators, this is supported by the sentence ”damage area of the accident aircraft was not accomplished in accordance with the Boeing SRM” (Aviation Occurrence Report ,2002, p.158). This suggests that the operators despite having the standard repair manual, did not use the manual when repairing the tail strike and thus is a contributing factor of the incorrect repair.
One other contributing factor for the incorrect repair was that the task given was too demanding for the operators. This is evident in the sentence Since the cut-out area was quite large, there would have been difficulty following the SRM repair instructions” (Aviation Occurrence Report, 2002, p.160). This means that the task was difficult to follow and adhere to due to the nature of the repair and the sheer size of the repair which could not be completely followed by the operators and maintenance personnel and thus contributes to the reason on why the repair was incorrectly done
Additionally, the technical skills and knowledge of the operators was a factor on why the repair was wrongly done. The phrase The damaged skin of B-18255 was beyond the allowable limit and scratches remained on the skin” (Aviation Occurrence Report ,2002, p.158) suggest that the operators did not know that the damage was beyond the repairable limit and yet still decided to repair the aircraft despite not knowing the issues the aircraft is affected with.
Not only that, the undocumented procedures and work process was another reason on why the repair was wrong. The sentence The Safety Council was unable to locate any documents regarding maintenance and inspection procedures at CAL in 1980 (Aviation Occurrence Report ,2002, p.133) and CAL did not accurately record some of the early maintenance activities before the accident, and the maintenance records were either incomplete or not found ” (Aviation Occurrence Report ,2002, p.222) suggest that operators could not refer to any past maintenance activities on repairing the damage thus led to them incorrectly repairing the structure.
Lastly, the communication problems between the two parties was a reason on why the structure was installed incorrectly this is evident in the sentence There was a problem in communication between Boeing Commercial Airplane Company and CAL regarding the tail strike repair in 1980. ” (Aviation Occurrence Report ,2002, p.6). This suggests that both China Airlines and Boeing could not decide on the appropriate repair as both had different views on the issue at hand thus affecting the operators repairing the damage which resulted in the wrongly installed structure.
3.3 Failure was not found by visual Inspection
Finally, the last reason for the fatal event was that the failure was not found during visual inspection of the plane. The reason being is that the information provided was inadequate for the operators to justify whether the repair done had any negative effects on the aircraft. This is supported by the sentence Due to the lack of detailed maintenance records for both the temporary and permanent repairs in 1980, the Safety Council was unable to determine how the repairs were conducted. (Aviation Occurrence Report, 2002, p.159).
Another reason for the failure not to be found during inspection was that the tools used were unreliable. This is evident in the sentence The crack would still not be detected if external high frequency eddy current had been used for structure inspection. Therefore, a more effective non-destructive structural inspection method should be developed to improve the capability of detection of hidden structural defects. (Aviation Occurrence Report ,2002, p.224) which suggest that the equipment during that period of time was considered unreliable as it could not detect the damage thus could not be found by visual inspection.
Additionally, complacency, an individual factor, was a reason on why the failure was not found by visual inspection. The phrase CAL personnel indicated that, for minor repairs, it was not necessary to inform the Boeing FSR because it would simply follow the SRM procedure to complete the repairs” (Aviation Occurrence Report ,2002, p.160) suggest that they did not require the expert opinion of the FSR as they assume that it was an ordinary repair like the one they were used to doing thus this is one of the reasons on why it was not found during visual inspection.
Finally, the environment especially the improper standard of lighting and cleanliness of the part was another reason on why the failure was not found during inspection. This is evident in “There is no lighting standard for CAL during a structural inspection and the magnifying glass was not a standard tool for structural inspections. ” (Aviation Occurrence Report ,2002, p.223) and “The bilge area was not cleaned before the 1st structural inspection in the 1998 MPV” (Aviation Occurrence Report ,2002, p.222) as now it will affect the operators judgement to see and feel the part to determine the parts serviceability thus is a factor on why the faults were not found during task inspection
4. Company Policy (Evaluate companys policies and procedures were effective in preventing such error)
As stated above in the informational contributing factor they did not follow information that was given in the Structural Repair Manual to repair the crack which was caused by the tail strike incident in Hong Kong airport and decided to just do a simple doubler patch repair without following proper procedures in accordance with the Structural Repair Manual.
Base on China Airlines policy Service Philosophy and Professional Ethics policy states that all employees need to know, be familiar and comply with respective national laws and company standards according to his or her profession. If the employee is unsure about any matter, they will have to consult somebody and to refrain from doing anything without approval. It is the duty of every employee in China Airlines to comply with the appropriate laws and regulations whenever he or she is doing their task and gets outcome.
Work safety policy tells us that when considering flight safety, China Airlines and employees has to comply with any appropriate request that arises from the need to increase safety.
Base on the communication factor there was an issue in communication with Boeing and China Airlines due to the tail-strike incident that happened in Chek Lap Kok International Airport, Hong Kong in 1980. As a representative for the field service from Boeing did not notice the defect that was on the underside of the aircrafts empennage. Due to this they did not get experts advice to tackle the defect which was missed. Since there were no records showing that the field service representative advises them to do a permanent repair on the defect.
In accordance with the values-supportive model of shared accountability, employees are required to report if there is any incident which will affect the flight and ground safety, involving dishonesty conduct by those with power or fail to comply with integrity to their supervisors or business management department. If any incidents are in progress, potential risks or negligence employees are required to stop or report the incident. All employees must know that serious negligence or international violation of the company policy is unacceptable behaviors.
5. Recommendation (New Layers of defense as espoused by Reasons Swiss Cheese Model)
Whenever an employee of China Airlines is seen performing structural repairs on the aircraft, they would have to comply with the Structural Repair Manual(SRM), or any other servicing agency approved methods without alteration and to perform damage assessment in accordance with the approved regulations, procedures and best practices.
Check through the aircraft maintenance records to ensure that all maintenance activities or tasks have been properly recorded into the aircraft logbook.
Evaluate and put into effect safety related airworthiness requirements, so that the Repair Assessment Program is before the usual practicable time.
Increase the maintenance crews awareness in relation to the irregular shape of the aircraft structure and the potential signs which may show hidden structure defect or damage.
FAA. 2002. Aviation Occurrence Report Volume I. [ONLINE] Available at: [Accessed 27 July 2019].
UKESSAYS. 2016. China Airlines Flight 611 Engineering Essay. [ONLINE] Available at: [Accessed 27 July 2019].
Tail Strike. 2002. 25 May 2002 – China Airlines 611. [ONLINE] Available at: [Accessed 26 July 2019].
Kiddle. 2019. China Airlines Flight 611 facts for kids. [ONLINE] Available at: [Accessed 22 July 2019].