Japan Airlines Flight 123

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Japan Airlines Flight 123 was a Japan Airlines domestic flight from Tokyo International Airport to Osaka International Airport on August 12, 1985. The Boeing 747-146SR that made this route, registered JA8119, suffered mechanical failures 12 minutes into the flight and 32 minutes later crashed into two ridges of Mount Takamagahara in Ueno, Gunma Prefecture, 100 kilometers from Tokyo. The crash site was on Osutaka Ridge , near Mount Osutaka. All 15 crew members and 505 out of 509 passengers died, resulting in a total of 520 deaths and four survivors. It is currently the deadliest single-aircraft accident in history, and the second deadliest plane crash in history behind the Tenerife airport disaster. The flight took off from Runway 16L at Tokyo International Airport in Ota, Tokyo, Japan at 6:12p.m., 12 minutes behind schedule. About 12 minutes after takeoff, as the aircraft reached cruising altitude over Sagami Bay, the rear pressure bulkhead was torn open. The resulting explosive decompression tore the tailfin from the aircraft and severed all four of the aircraft's hydraulic systems. A photograph taken from the ground some time later confirmed that the vertical stabilizer was missing. The loss of cabin pressure at high altitude had also caused a lack of oxygen throughout the cabin, and emergency oxygen masks for passengers soon began to fall. Flight attendants, including one who was off-duty and flying as a passenger, administered oxygen to various passengers using hand-held tanks. The pilots, including Captain Masami Takahama, first officer Yutaka Sasaki, and flight engineer Hiroshi Fukuda, set their transponder to broadcast a distress signal to Tokyo Area Control Center, which directed the aircraft to descend and gave it heading vectors for an emergency landing. Continued control problems required them to first request vectors back to Haneda, then to Yokota a U.S. military air base, then back to Haneda again as the aircraft wandered uncontrollably. By then all hydraulic fluid had drained away through the rupture. With total loss of hydraulic control and non-functional control surfaces, the aircraft began to oscillate up and down in a phugoid cycle. The pilots managed a measure of control by using differential engine thrust. These improvisations proved helpful, but further measures to exert control, such as lowering the landing gear and flaps, interfered with control by throttle, and the plane's uncontrollability once again escalated. After descending to 13,500 feet, the pilots reported the aircraft's uncontrollability. The plane flew over the Izu Peninsula, headed for the Pacific Ocean, then turned back towards the shore and descended to below 7,000 feet before the pilots managed to return to a climb. The aircraft reached an altitude of 13,000 feet before entering an uncontrollable descent into the mountains and disappearing from radar at 6:56 p.m. and 6,800 feet. The final moments of the plane occurred when it clipped one mountain ridge then crashed into a second one during another rapid plunge, then flipped and landed on its back. The official cause of the crash according to the report published by Japan's then Aircraft Accidents Investigation Commission is as follows: The aircraft was involved in a tailstrike incident at Osaka International Airport on 2 June 1978, which damaged the aircraft's rear pressure bulkhead. The subsequent repair of the bulkhead did not conform to Boeing's approved repair methods. The Boeing technicians fixing the aircraft used two separate doubler plates, one with two rows of rivets and one with only one row while their procedure calls for one continuous doubler plate with three rows of rivets to reinforce the damaged bulkhead. This reduced the part's resistance to metal fatigue by 70%. When the bulkhead gave way, the resulting explosive decompression ruptured the lines of all four hydraulic systems and blew off the vertical stabilizer. With the aircraft's flight controls disabled, the aircraft became uncontrollable. [READ THE REST OF THIS ARTICLE]

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