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Metal fatigue in old aircraft 老旧飞机的金属疲劳 Flying rivets 飞行侦查兵 A new technique that listens for cracks in ageing aircraft 一项侦听老化飞机断裂的新技术 WHEN they were built, no one thought they would fly for so long. 建造飞机的时候，没人认为它们会飞行这么久。 But fitted with new engines and avionics, aircraft can be kept going for a very long time. 但是装有新式引擎和航空电子设备的飞机能持续飞行很长一段时间。 The average age of the world s airliners is more than ten years, with some passenger jets 25years old or more. 全世界飞机的平均机龄超过10年，有些客机的机龄超过了25年。 Military planes are more geriatric: the Sikorsky Black Hawk helicopter entered service 31years ago and the Lockheed C-5 Galaxy 40 years back. 军用飞机更是超龄：西科斯基公司的黑鹰直升机31年前开始服役，洛克希德公司的C-5银河早用到40年了。 Both are still going strong. 这两款飞机还都强劲地飞行着。 Some Boeing KC-135 aerial-refuelling planes, which are based on the venerable 707, havebeen flying for over 50 years. | 
