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Aviation History
1985
1985 - 2479.PDF
AIR TRANSPORT which filled with a white cloud. She noticed damage above a lavatory, four rows behind her seat. The oxygen masks automatically deployed. She says that the aircraft began a dutch roll (pitching, rolling, and yawing). She could tell the aircraft was off course because she saw Mt Fuji on the port side. She breathed oxygen for about lOmin before the supply gave out, during which time f the aircraft had descended. After helping passengers into k their life-vests she returned to he*r seat. Mrs Ochiai said that there was a sudden steep and rapid dive followed by two or three violent shocks. The 747SR which crashed had been involved in two previous incidents. In 1978 ithe tail section was badly damaged when it was dragged along the runway while the aircraft was landing at Osaka. Some 30 people were injured. rThe lower part of the tail section fuselage and the tail plane were replaced by Boeing ^ in Japan, but not the vertical fin. In the second incident, in *1982, the aircraft scraped the ground with the No. 4 engine at Chitose Airport. *" The 747SR has a maximum capacity of 550, although the * one that crashed was config ured for 528 passengers. The aircraft is a short-range version of the 747-100B embodying structural changes /-for high take off and landing cycles. The JAL examples of the type have maximum take- 'off weights up to 603,0001b compared with 833,0001b for <747-200s. In addition to Japan's Civil Aviation Board, a team of five ''Boeing officials and two investigators from both the ^US FAA and the US National Transportation Safety Board are on the crash site. The "flight data recorder and the cockpit voice recorder were * recovered within days of the accident, although analysis of the FDR was delayed because * it was in very poor condition. Japan's investigation r bureau, which is in charge of the operation, was set up in the wake of a crash in March 1966 in which a BOAC Boeing 707 broke up in mid-air over Mt Fuji after losing its fin, killing 124 people. Its systems were set up with the advice of several other leading author ities, including the UK Civil Aviation Authority. FLIGHT International, 24 August 1985 Failure theories examined The UK Civil Aviation Authority issued an Emergency Airworthiness Directive 009-08-85 on August 16 requiring within ten days the following "precautionary inspec tions" of all British- registered 747s with more than 5,000 landings: inspection of the internal aft fuselage structure from the stations 2360 (pressure dome) to 2517 including the rear face of the pres sure dome; the internal structure of the vertical stabiliser up to fin station 420; and an external visual check of the area around station 2280 (where the fin auxiliary spar link is attached to the fuselage). The bottom of the pres sure dome is known to be subject to corrosion from lavatory spillage, and is routinely inspected, cleaned, and treated. The 747 has no history of decompression incidents in this area, but the consequences of a major fracture and decom pression could fit the known facts, including the finding of parts of the upper fin under the initial flightpath. The JAL tech nical manager has said that air escaping from the cabin into the fin could have caused the fin to burst. Such a failure sequence occurred to a BEA Vanguard over Belgium in 1971 with the loss of all on board: corro sion in the lower part of the pressure bulkhead—an area which could be subject to lavatory spillage— caused a rupture which inflated and burst a tail- plane. The Boeing telex to operators suggests that they may wish to inspect the aft portion of the pres sure hull, as well as the areas itemised above by the JCAB. Early theories about sabotage have been unoffi cially discounted by the Japanese. So has the suggestion that the aft starboard passenger door separated and struck the tailplane. It is now believed that the cockpit warning light relating to this door was activated by structural distortion. This door did not open, according to the surviving stewardess. Airworthiness experts on the 747 structure do not rule out the pressure bulk head corrosion theory, but say that it is not the only one. Fin failure could have been initiated in other unspecified ways, and the general feeling is that all parts of the 747 tail struc ture must be specially re- inspected until the acci dent investigators have narrowed down the suspect areas. One 747 airline engineer acknowledges the validity of the pressure bulkhead corrosion theory, and its Vanguard analogy, but emphasises that it is "only one option".
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