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Published on Jun 4, 2009
Japan Airlines Flight 123 was a Japan Airlines domestic flight from Tokyo International Airport (Haneda) to Osaka International Airport (Itami). The Boeing 747-SR46 that made this route, registered JA8119, suffered mechanical failures 12 minutes into flight and 32 minutes later crashed into two ridges of Mount Takamagahara in Ueno, Gunma Prefecture, 100 kilometers from Tokyo, on Monday 12 August 1985. The crash site was on Osutaka Ridge (おすたかのおね, Osutaka-no-One), near Mount Osutaka. All 15 crew members and 505 out of 509 passengers died, resulting in a total of 520 deaths and 4 survivors. It remains the deadliest single-aircraft accident in history. The official cause of the crash according to the report published by Japan's then Aircraft Accidents Investigation Commission is as follows:
1. The aircraft was involved in a tailstrike incident at Osaka International Airport on 2 June 1978, which damaged the aircraft's rear pressure bulkhead. 2. The subsequent repair of the bulkhead did not conform to Boeing's approved repair methods. Their procedure calls for one continuous doubler plate with three rows of rivets to reinforce the damaged bulkhead, but the Boeing technicians fixing the aircraft used two separate doubler plates, one with two rows of rivets and one with only one row. This reduced the part's resistance to metal fatigue by 70%. According to the FAA, the one "doubler plate" which was specified for the job (the FAA calls it a "splice plate" - essentially a patch) was cut into two pieces parallel to the stress crack it was intended to reinforce, "to make it fit". This negated the effectiveness of two of the rows of rivets. During the investigation Boeing calculated that this incorrect installation would fail after approximately 10,000 pressurizations; the aircraft accomplished 12,319 take-offs between the installation of the new plate and the final accident. 3. When the bulkhead gave way, the resulting explosive decompression ruptured the lines of all four hydraulic systems. With the aircraft's control surfaces disabled, the aircraft became uncontrollable.
This is the CVR (Cockpit Voice Recorder) recorded while the accident was happening.