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In 2002, two large airtankers – a C-130 Hercules and a PB4Y-2 Privateer – crashed about a month apart while performing aerial firefighting operations. These crashes prompted a review of the maintenance and use of the entire U.S. large airtanker fleet. Ultimately, the whole fleet (33 aircraft in all) was grounded, dramatically reducing the resources available to fight major wildfires. Both aircraft were owned by Hawkins & Powers Aviation of Greybull, Wyoming and operated under contract to the U.S. Forest Service (USFS). The crashes occurred in one of the worst fire seasons in the last half century, one in which 73,000 fires burned of land.〔 ==C-130A, N130HP, Walker, California== N130HP, call sign "Tanker 130", was flying against the Cannon Fire,〔The Cannon Fire started June 15, 2002 and was 100% contained on June 28, 2002, after burning ()〕 near Walker, California on June 17, 2002, when it experienced structural failure of the center wing section, causing both wings to fold upward and separate from the aircraft. The fuselage rolled and crashed inverted, killing the three crewmen on board. Tanker 130 had departed the Minden, Nevada air attack base at 2:29 p.m. PDT with of fire retardant for its sixth drop of the day, and arrived at the fire at 2:45 p.m. The crew made an initial spotting pass over the drop zone, then flew back for the drop, which was to be a 1/2 salvo, dispensing half of the onboard retardant. The drop run required the aircraft to make a perpendicular crossing of a ridgeline and then descend into a valley. A video of the accident shows the aircraft crossing the ridge and then pitching down to begin its drop of the retardant. Near the end of the drop, the nose of the aircraft began to pitch up to level attitude as the descent was arrested. The nose continued to pitch up past level attitude, and at the end of the drop, the right wing began to fold upwards, followed less than one second later by the left wing. Two debris fields were found, one in length and the other in length. A post-impact fire in the first debris field consumed major portions of the wing and engine components; there was no fire in the second debris field, which included the fuselage and empennage.〔 The aircraft, serial number 56-0538, was one of the original C-130 production series and had been built by Lockheed and delivered to the USAF in 1957. It was retired from military service in 1986. In May 1988, the aircraft was acquired by the U.S. Forest Service from the General Services Administration, and in August 1988 the Forest Service sold the plane to Hemet Valley Flying Service along with five others it had acquired, for conversion to an airtanker. Hemet then sold the C-130 to Hawkins & Powers.〔 At the time of the crash, the airframe had logged 21,863 flight hours.〔 The National Transportation Safety Board (NTSB) investigated the crash and determined that the accident was caused by a structural failure which occurred at the wing-to-fuselage attach point, with the right wing failing just before the left one. The investigation disclosed "evidence of fatigue cracks in the right wing's lower surface skin panel, with origins beneath the forward doubler.... The origin points were determined to be in rivet holes which join the external doubler and the internal stringers to the lower skin panel. These cracks, which grew together to about a length, were found to have propagated past the area where they would have been covered by the doubler and into the stringers beneath the doubler and across the lap joint between the middle skin panel and the forward skin panel."〔〔("Update on Investigations of Firefighting Airplane Crashes in Walker, California and Estes Park, Colorado", National Transportation Safety Board, September 24, 2002, retrieved September 6, 2007 )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2002 United States airtanker crashes」の詳細全文を読む スポンサード リンク
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