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A bird strike—sometimes called birdstrike, bird ingestion (for an engine), bird hit, or BASH (for Bird Aircraft Strike Hazard)—is a collision between an airborne animal (usually a bird or bat) and a human-made vehicle, especially aircraft. The term is also used for bird deaths resulting from collisions with human-made structures such as power lines, towers and wind turbines (see Bird-skyscraper collisions and Towerkill). Bird strikes are a significant threat to flight safety, and have caused a number of accidents with human casualties. The number of major accidents involving civil aircraft is quite low and it has been estimated that there is only about 1 accident resulting in human death in one billion (109) flying hours. The majority of bird strikes (65%) cause little damage to the aircraft; however the collision is usually fatal to the bird(s) involved. Most accidents occur when there is a collision involving a bird (or birds) and the windscreen or a bird (or birds) is sucked into the engines of mechanical air craft. These cause annual damages that have been estimated at $400 million〔 within the United States of America alone and up to $1.2 billion to commercial aircraft worldwide.〔 In addition to property damage, collisions between man-made structures and conveyances and birds is a contributing factor, among many others, to the worldwide decline of many avian species. Related to this is a bug strike: an impairment of an aircraft/groundcraft or aviator/driver by an airborne insect. ==Event description== Bird strikes happen most often during takeoff or landing, or during low altitude flight. However, bird strikes have also been reported at high altitudes, some as high as to above the ground. Bar-headed geese have been seen flying as high as above sea level. An aircraft over the Ivory Coast collided with a Rüppell's vulture at the altitude of , the current record avian height.〔Thomas Alerstam, David A. Christie, Astrid Ulfstrand. ''(Bird Migration )'' (1990). Page 276.〕 The majority of bird collisions occur near or on airports (90%, according to the ICAO) during takeoff, landing and associated phases. According to the FAA wildlife hazard management manual for 2005, less than 8% of strikes occur above and 61% occur at less than 30 m (100 ft). The point of impact is usually any forward-facing edge of the vehicle such as a wing leading edge, nose cone, jet engine cowling or engine inlet. Jet engine ingestion is extremely serious due to the rotation speed of the engine fan and engine design. As the bird strikes a fan blade, that blade can be displaced into another blade and so forth, causing a cascading failure. Jet engines are particularly vulnerable during the takeoff phase when the engine is turning at a very high speed and the plane is at a low altitude where birds are more commonly found. The force of the impact on an aircraft depends on the weight of the animal and the speed difference and direction at the impact. The energy of the impact increases with the square of the speed difference. Hence a low-speed impact of a small bird on a car windshield causes relatively little damage. High speed impacts, as with jet aircraft, can cause considerable damage and even catastrophic failure to the vehicle. The energy of a bird moving at a relative velocity of approximately equals the energy of a weight dropped from a height of .〔Note however that the momentum (as distinct from the kinetic energy) of the bird in this example is ''considerably'' less than that of the tonne weight, and therefore the force required to deflect it is also considerably less.〕 However, according to the FAA only 15% of strikes (ICAO 11%) actually result in damage to the aircraft. Bird strikes can damage vehicle components, or injure passengers. Flocks of birds are especially dangerous, and can lead to multiple strikes, and damage. Depending on the damage, aircraft at low altitudes or during take off and landing often cannot recover in time, and thus crash, as in the case of US Airways Flight 1549. Remains of the bird, termed ''snarge'', are sent to identification centers where forensic techniques may be used to identify the species involved. These samples need to be taken carefully by trained personnel to ensure proper analysis and reduce the risks of zoonoses. The Israeli Air Force has a larger than usual birdstrike risk as Israel is on a major spring and autumn long-distance bird migration route. Sacramento International Airport has had more bird strikes (1,300 collisions between birds and jets between 1990 and 2007, causing an estimated $1.6 million in damage) than any other California airport. Sacramento International Airport has the most bird strikes of any airport in the west and sixth among airports in the US, according to the FAA, as it is located along the Pacific Flyway, a major bird migration path.〔(SMF Tops California Airports For Bird Strikes 100 Bird Strikes Reported Annually In Sacramento, Experts Say January 15, 2009 )〕〔(Sacramento airport seeks bird-kill law for air safety )〕 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「bird strike」の詳細全文を読む スポンサード リンク
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