Japan Airlines Flight123, Boeing 747-SR100, JA8119/FAA

Posted on: 17th May 2023


Japan Airlines Flight 123, Boeing 747-SR100, JA8119/FAA


Explore the aircraft maintenance, inspection, repair, or alteration flaws, often involving errors or faulty assumptions during the maintenance process. Be sensitive to discover what the flaws, errors and faulty assumptions were. Analyze this case study in terms of mechanical and structural factors and provide a technical report which analyzes this accident.

1. Title or Cover Page

2. Introduction or executive summary

3. Primary Causal Factor(s) of the Accident

4. Contributing Factors to the Accident

5. Structural and Mechanical Factors Related to the Accident

6. Relevant Human Factors and/or Organizational Factors Related to the Accident

7. Outcomes of the Accident

8. Risk Mitigation or Reduction Strategies

9. Conclusion or Summary

10. Reference Page

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Japan Airlines Flight123, Boeing 747-SR100, JA8119/FAA

On June 12, 1988, Japan Airlines Flight 123 was a routine Japanese domestic flight from Tokyo International Airport to Osaka International Airport that crashed shortly after take-off (Administration, 1985). The airplane’s pilot reported difficulties soon after departure and gave his position 55 miles southwest of Tokyo (Jackson, 1985), which would put the flight on course for Alaska. However, the flight lost control twelve minutes after take-off from Tokyo airport on August 12, 1985, as it approached a cruising height of 7,200m (Hideo & Hiroyuki, 1985). The plane experienced an exploding decompression as a result of the aft bulkhead's rapture (Administration, 1985). The aft bulkhead became fatigued, followed by the vertical fin's structural failure (Administration, 1985). Finally, after thirty-two minutes of irregular flight, the flight was crushed at Mt. Takamaghara, Ueno, Gunna Prefecture (Hideo & Hiroyuki, 1985). The fuselage, empennage, and much of the control surfaces were all destroyed (Hideo & Hiroyuki, 1985). Five hundred twenty people were killed in the collision (15 crew and 505 passengers), accounting for almost half of the 524 individuals on board, the most catastrophic single-aircraft accident in history (“Japan airlines 123 CVR transcript,” n.d.).

Primary Casual Factors of the accident

The accident’s causes revealed numerous contributing factors that resulted in the tragedy, including several concerns that caused it. The root cause of the crash was the improper repairs made on the plane several years before the accident (Administration, 1985). In June 1978, the aircraft received large-scale repairs at the maintenance field at Haneda after experiencing a tail hit landing at the Osaka airport (Hideo & Hiroyuki, 1985). The tail of the aircraft struck the runway, causing a mechanical failure and vulnerable pressure points on the plane bulkhead (Administration, 1985). The consistent repair of the damaged bulkhead was not conducted following the company’s procedure, and two separate slice plates instead of a single plate were used during the repair. As a result, the entire load was transmitted through the center rivet row only, and multiple site fatigue cracks were initiated from the rivet holes of the center row soon after repair. The fatigue failure was due to a mistake made during the repairs at that time. Over time, the airplane bulkhead was pushed and pulled by the pressures on both sides. As a result, explosive decompression ruptured the flight’s hydraulic systems. The damage to the hydraulic systems disabled the flight controls, lending the plane uncontrollable.

Contributing factors to the accident

Maintenance errors were made on the aircraft over time, such as the bulkhead repair with the improper installation of plates to strengthen it. This gave in to the force after a failed row rivets implementation, which resulted in a reduced effect. In addition, the maintenance engineers’ failure to understand the fundamental mechanism of load transmission and preliminary inspection by the airline representatives are also contributing factors to the crash.

Structural & Mechanical factors related to the accident

Another consideration is the structural failure during flight, which was a significant element in its status. The failure was caused by the airplane's systems being repeatedly subjected to high and low air pressure (“Japan Airlines 123 CVR transcript,” n.d.). Furthermore, the falling of the bulkhead caused severe hydraulic failure due to the catastrophic decompression initiated by the failure of the aircraft’s control systems. As a result, while the pilot was able to keep the plane in the air for approximately 32 minutes and avoid a mid-air explosion, the disabled flight controls rendered the plane uncontrollable, leading to the fatal crash (“Japan Airlines 123 CVR transcript,” n.d.).

Relevant human and organizational factors related to the accident

The maintenance engineers responsible for the repairs made on the flight did not understand the fundamental mechanism of load transmission and conducted faulty repairs. Additionally, the airline representatives and air transportation authorities who should have identified the mistakes during the inspection were unreliable. The site of the repair mistake was covered with sealant (Hideo & Hiroyuki, 1985). However, with a thorough inspection, the mistake would have been identified.

The outcome of the accident

Japan airline flight 123 crash involved the largest loss of life for any single air crash worldwide, where 520 lives were lost. The pilot sent out a distress signal that was picked up by United States Air Force controllers at the Yokota Air Base, and transmission with the flight was lost (Hood, 2013). The U.S. air force discovered the flight 90 minutes after the accident, but rescue was not attempted due to the conflicts between the U.S. and Japanese air forces. Rescuers had great difficulty reaching the crash site (Jackson, 1985) because of the harsh conditions. The harsh conditions and lack of emergency medical assistance may have caused the death of more passengers. According to (Jimbo, 1991), the compensation amount to the affected families was not disclosed. Also, following the accident, the company president resigned.

Risk mitigation or Reduction strategies

Removing human factors in systems is difficult. Accidents such as this are caused solely by human errors. Maintenance operations and inspections are complex in the aviation industry and require accuracy. To avoid such catastrophes and assure the public’s safety, rigorous inspections should be done after major repairs have been completed to ensure that the plane is in excellent operating order. Fundamental training and education in areas such as mechanics of materials should be offered in detail, even for the engineers on the site. Moreover, the authorities signing the approval documents after repair should carefully check that all repairs are correctly done. Also, operators should be supplied with tools to perform experiments and test hypotheses to make acceptable performance limits visible.

Furthermore, minor and major plane mistakes must be taken seriously regarding repair, upkeep, and upgrading. Also, the rules and regulations of airline manufacturing businesses should be taken into account while performing maintenance on an aircraft. It is essential to hire a professional who can handle the installation and fabrication of parts and ensure that all components are approved in case of the need to replace airplane components.


The leading cause of the accident was the mistake made during the repair of the bulkhead after the plane scraped the runway. However, the direct cause of the airplane losing control is the loss of the hydraulic control unit and the vertical fin. The repair work’s final check, conducted by the airline’s representatives and air transport authority, was also insufficient. In addition, maintenance engineers did not understand the fundamental mechanism of load transmission. Many families suffered the loss of their loved ones since most passengers were Japanese traveling to celebrate the religious festivals of Obon. Being a fatal single plane crash worldwide, it remained historical and a sore topic for everyone. The japan airline flight 123 was a jumbo jet used and trusted by many people, and concerns were raised after the tragedy about whether the problem was common to the fleet. As a result, the airline lost its credibility and took a long time to recover from the incident.

It is difficult to eliminate the human factor in some systems. However, errors that can lead to considerable loss of lives can be controlled differently; for instance, hypothetical analysis by operators to determine the performance and safety of a system. Inspections in aviation can be crucial but achievable. Inspections regularly and every time a plane undergoes repairs can make it easier for the authorities to detect any fault. Before signing off a plane as viable for take-off, the authorities should double-check to ensure no errors were made. In addition, thorough inspections should be conducted on the planes before take-off to ensure the safety of passengers. Large systems are often prone to fault and can cause huge damages, but proper repairs, testing, and thorough inspections can minimize casualties.



Administration, F. A. (1985, August 12). Boeing 747-SR100 Japan Airlines Flight 123, JA8119. Federal Aviation Administration. https://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=16&LLTypeID=0

Hood, C. P. (2013). Dealing with disaster in Japan: Responses to the flight JL123 crash (1st ed.). Routledge.

Jackson, H. (1985, August 13). 524 killed in worst single air disaster. News, sport and opinion from the Guardian’s U.S. edition | The Guardian. https://www.theguardian.com/fromthearchive/story/0,,1017027,00.html

Japan airlines 123 CVR transcript. (n.d.). Cockpit Voice Recorder Database. https://tailstrike.com/database/12-august-1985-japan-airlines-123/

Jimbo, T. (1991, March 26). Boeing and JAL crash victims’ families settle compensation suit. AP NEWS. https://apnews.com/article/90247f31aff0e8a4c8fb99eb7e90f77f

Kobayash, H., & Terada, H. (2008). Crash of Japan Airlines B-747 at Mt. Osutaka

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