Japan Airlines Flight 123
The Japan Airlines Flight 123 best refers to the accident that occurred on August 12, 1985, which is one of maintenance-related failures in aviation.
Description
On August 12, 1985, the Japan Airlines Flight 123 suffered mechanical failures 12 minutes into the flight and 32 minutes later crashed into a mountain while killing 15 crew members and 509 passengers on board. Till now, this is the second deadliest disaster in the history of aviation.
The aircraft was involved in a tail strike incident seven years earlier, on 2 June 1978, which damaged the rear bulkhead. However, the repair of the damaged section had not been properly repaired. When replacing the damaged pressure wall plate, a whole joint plate should be used to connect the two panels to be connected and three rows of rivets should be used to fix them, but the maintenance personnel used two discontinuous joint plates, one with one row of rivets and the other with two rows of rivets. This results in a significant increase in stress on the metal skin near the joint and a reduction in resistance to metal fatigue of at least 70%.
The metal used in the repairs can only withstand about 10,000 flights, and the Flight 123 was the 12319th flight after the crash. During the flight several years after maintenance, metal fatigue accumulated in the cabin due to repeated pressurization and decompression. Eventually, the rear bulkhead gave way leads to the failure of all 4 hydraulic systems, which disabled the aircraft's control disabled and, when the aircraft became uncontrollable, led to the disaster.
When the aircraft climbed to about 7,000 meters, the accumulated metal fatigue of the pressure wall panel reached the limit, and it could no longer bear the pressure difference and break. As a result, explosion and decompression occurred in the engine room. High pressure air rushed into the tail, blowing down the vertical tail directly and tearing off the main hydraulic pipeline, which made the pilot unable to control the aircraft normally.
The pilots and engineers on the wrecked plane struggled with the plane for half an hour under the condition of nearly completely out of control, showing great efforts. Instead of failed hydraulic systems, the pilots heroically used the engine accelerations and de-accelerations to direct the plane. However, the huge size of the plane and continuous mountain terrain made their task impossible. After the accident, no investigators and pilots who simulated the situation at that time could fly for half an hour under the same circumstances.
