roberto_vargas_6.2_Case Study Analysis_Accident Research

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1 Case Study Analysis 6.2: China Airlines Flight CI611 Roberto L. Vargas Embry Riddle University BSAS 335: Mechanical and Structural Factors in Aviation Safety Dr. Thomas L. Holmes Jr November 26, 2023

2 Introduction On May 25, 2002, China Airlines Flight CI611 a Boeing model 747-200 series aircraft had an inflight breakup due to structural failure of the aft lower lobe section ( Boeing 747-200, 2022). This area of the aircraft was repaired permanently on May 25, 1980, after blending the affected area that was damaged due to a tail strike on February 7, 1980 ( Boeing 747-200, 2022). In this case study I will attempt to explain my findings regarding the accident and the events that lead up to it. I will go over the repair procedures and the execution of these procedures by the technicians and how they differ from what should have been done. Primary Causal Factors of the Accident In my research, I believe that the primary cause of the in-flight breakup of Flight CI611 was the separation of the tail section of the aircraft. It seems to have had a structural weakness at the aft lower lobe of the aircraft where it was believed to have been repaired 22 years before. The area around the previous repair to the tail strike in 1980 ( In-Flight Breakup, 2003). Figure 1 Evidence of Failed Doubler Note: Failed doubler from the Crash of Flight CI611 from the Aviation Occurrence Report Volume 1

3 Due to the incident in 1980, the damaged area failed with fatigue cracking around the STA 2100 area of the aircraft. These cracks were evident around the doubler in that area and seemed to propagate alongside it ( In-Flight Breakup, 2003). Contributing Factors to the Accident Some of the contributing factors to this accident come in the form of the incident that happened in 1980, Improper maintenance practices, and a break in the inspection process for that repair. It seems in the documentation that some of the criteria to repair the damage done to the aircraft were not accomplished to the specifications of Boeing and therefore weakened the affected area of the aircraft. This action, if taken correctly, could have prevented the event on May 25, 2002, from happening, leading to the in-flight breakup. First, the incident that weakened the aft lower lobe of the 747 aircraft on February 7, 1980, caused significant scratches when landing at Kai Tec Airport Hong Kong ( Boeing 747- 200, 2022). This is where it was decided to temporarily repair the scratches with two doublers made of aluminum 7075-T6 alloy. It was to be replaced in four months with a permanent repair that was accomplished according to the Boeing 747 structural repair manual (SRM)

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4 Leading up to the permanent repair on May 25, 1980, which had the permanent doubler where the previous doubler had been for the temporary repair as they blended the scratches but did not Figure 2 Temp repair instructions Note: The documentation to instructions for a temporary repair of structural damage.

5 fully remove the damaged area with minimal documentation of the repair since it was considered a minor repair ( In-Flight Breakup, 2003). The mechanics working the repair did not fully blend the damaged area to get rid of the scratches. Nor did they extend the doubler past the damaged area as the SRM instructed it to do so that the load on the skin could be transferred around the damaged area ( In-Flight Breakup, 2003). Since the repair was applied directly to the affected area and not around it then the damaged area bares the load. Especially on a pressurized vessel the doubler should have extended around the area that was damaged and sealed to reinforce it which would have been a common practice at the time Figure 3 Skin scratches on aft lower lobe Note: This is the damaged area of the lower lobe that show the scratches not fully blended away

6 ( Typical repairs for aircraft structures (part 1), 2023). Also, the inspection of this area throughout the aircraft history was undermined. The inspection requirements for the Corrosion Prevention and Control Program (CPCP) had 29 items inspection items that were not accomplished in the maintenance records ( In-Flight Breakup, 2003). Structural and Mechanical Factors Related to the Accident For structural and mechanical-related factors of this accident seem to be on structural failure of this repair area. The flight recorder retrieved from the accident site showed all systems were performing nominally up to the point when they were cut off from their power supply ( In- Flight Breakup, 2003). This was another factor that led to the understanding that the aft tail section separated first in flight. The flight recorders were attached to the main power supply that was separated from the tail section. No other information after this point would lead investigators to believe that any system or mechanical issue contributed to the accident. The sections of aircraft retrieved from the crash site included the doubler repair that led investigators to believe that this section had failed. Since this was not correctly repaired the doublers that were to repair the area were not big enough to cover the affected area according to Boeing standards of repair in their SRM. This causes the affected area to fatigue and crack over time extending from the original scratches that were not fully blended or removed ( Boeing 747- 200, 2022). The continued cycling of the aircraft being pressurized and the stress loading in this area caused these cracks to propagate out alongside the rivet hole of the doublers. Relevant Human Factors and Organizational Factors Related to the Accident The human factor of this accident stems from the actions of the repair team back in 1980 that accomplished the repair. China Airlines also did not seem to have reached out to a Boeing

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7 Representative in Hong Kong (BFSHKG) for advice on the repair process ( In-Flight Breakup Volume 2, 2003). They could not validate the work being performed which would have raised red flags for the Boeing representatives. It’s hard to determine if CAL did this on purpose or if they weren’t familiar with the procedures for informing Boeing of their repair SRM, but it looks like it was overlooked. The inspections that need to be performed were missed during the CPCP inspection. Some of the findings state that 29 items from the PCP inspection in November 1997 and onward were not checked. These inspection points, especially for aging aircraft like this Boeing 747 are essential to the continued health of the aircraft ( In-Flight Breakup Volume 2, 2003). These types of inspection are designed to seek out different levels of corrosion including fatigue and cracks that are starting to propagate. Although the doublers that were installed hid a lot of the cracks that were growing underneath it there was evidence of cracking around the doublers to suggest that there was damage underneath. Dark traces of stains in the areas of the doublers were evidence of a small preach in the pressure seal of the aircraft ( Boeing 747-200, 2022). Figure 4 Dark strains around Note: The staining outside the doubler indicating a preach in the pressure seal.

8 Outcomes of the Accident After the investigation of this accident, the Aviation Safety Council (ASC) issued an Interim Flight Safety Bulletin to ICAO for an aircraft pressurization structure repair alert supply ( In-Flight Breakup, 2003). This included added wording to the engineering orders stating that “Hidden structural damage can cause aircraft structure failure” ( In-Flight Breakup, 2003). Also needed to include step-by-step instructions, detailed drawings, Required Item Inspection (RII), and categorize the repair as a major. China’s Civil Aviation Administration (CAA) grounded all 747-200 in the China Airlines fleet to ensure no other repairs like this one had cracks or were improperly repaired (Wong, 2022). CAL had reviewed its self-audit inspection procedures to better catch the deficiency of oversight to missing inspection points. Establishing an Engineering Planning Department (EPD) on May 10 th , 2004, to integrate planning, control, work order issues, and other functions to aid in this process ( In-Flight Breakup, 2003). Boeing NDI staff now use new technologies and procedures to aid in the detection of repairs like tail strikes ( In-Flight Breakup, 2003). The FAA considered the implementation of an independent power source for the flight recorders to function if the main power supply is severed ( In-Flight Breakup, 2003). This is a common practice today with flight recorders or “Black boxes” to have an independent power supply that is inspected in several calendar days ( Flight data recorder, 2014). Risk Mitigation or Reduction Strategies After reviewing all the evidence of this accident and what was overseen when conducting the repairs I would suggest adequate training in handling repairs like the one for flight CI611. As an Aircraft mechanic and Structures mechanic, I can say from my work

9 experience that once you start working in this occupation uncommon repair or unique repairs do not have training associated with them for best practices or lessons learned. Even as an experienced mechanic, I can say I get complacent and so do many of my colleagues. I have rarely seen companies take the initiative to train their employees how to handle repairs like this knowing what best practices are to aid in familiarizing with procedures. These can be complex repairs and their level of importance is understated sometimes when mentioned. The assumption that most technicians will always remember or know how to approach a repair even though it may not be routine is a flaw in logic. Not having some kind of inspection process after the repair was done to ensure all the scratches were completely removed or blended out was something else that could have been avoidable. Today I don’t see how an inspection point was not created to ensure that the repair was done even if it was considered a minor repair. To consider a repair that needs doublers and is supposed to divert the load away from the affected area seems to be a miscommunication. Pressure vessels need to be treated as fatigue-critical areas due to the purpose of pressure vessels in the atmosphere. After accidents like the Comet 1 that happened decades before this accident, I would have imagined that any alteration or modification of a pressure vessel would be considered more serious. Conclusion After reviewing this case study of the Boeing 747-200 it has brought me perspective on why some of the repairs that I've witnessed are meant with harsh scrutiny when inspected. It is hard to understand the gravity of what I work on every day if I have nothing to compare it to. The reason why we take our procedures seriously is due to accidents like the China Airlines Flight CI611. It is important to share cases like this with the technicians, and mechanics whose

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10 people’s lives are in their hands. I believe that there should be weekly reviews of case studies like this for these technicians and professionals to remind them of the importance of their jobs. I have not seen any employer I've worked for making this kind of effort to the importance of their workmanship. References Aviation Safety Council. (2003, June 3). In-Flight Breakup over the Taiwan Strait Northeast of Makung, Penghu Islands China Airlines Flight CI611 Boeing 747-200, B-18255 . Volume 2. Federal Aviation Administration. https://www.faa.gov/sites/faa.gov/files/2022-11/CI611_English_VOL_1.pdf Aviation Safety Council. (2003a, June 3). ). In-Flight Breakup over the Taiwan Strait Northeast of Makung, Penghu Islands China Airlines Flight CI611 Boeing 747-200, B-18255. Volume 2 . Federal Aviation Administration. https://www.faa.gov/sites/faa.gov/files/CI611_English_VOL_2.pdf Blogger. (2023, May 22). Typical repairs for aircraft structures (part 1) . Aeronautics Guide. https://www.aircraftsystemstech.com/2017/06/typical-repairs-for-aircraft-structures.html Boeing 747-200 . Federal Aviation Administration. (2022a, December 19). https://www.faa.gov/lessons_learned/transport_airplane/accidents/B-18255 University of Missouri. (2014, May 21). Flight data recorder batteries are long overdue for an upgrade, MU researcher suggests . Aviation Pros. https://www.aviationpros.com/engines- components/aircraft-airframe-accessories/batteries/news/11474884/flight-data-recorder- batteries-are-long-overdue-for-an-upgrade-mu-researcher-suggests Wong, D. (2022, May 22). Deadly Metal Fatigue: The story of china airlines flight 611 . Simple Flying. https://simpleflying.com/china-airlines-flight-611-metal-fatigue-story/