万里长天，雄鹰比翼，航空作战已成为现代战争中最重要的组成部分之一。不过传统的飞机都需要一个宽阔平坦的场地供其起降使用，这无疑使飞机的机动灵活性大打折扣。人们渴望有一种不需要特殊场地即能自如起落的飞行器，于是直升机便应运而生了。直升机具有垂直起降和空中悬停 Miles long days, Eagle wings, aviation operations has become one of the most important part of the modern war. However, the traditional aircraft require a wide and flat space for its take-off and landing, which will undoubtedly reduce the flexibility of the aircraft. People are eager to have a kind of aircraft that can move freely without special space, so the helicopter came into being. Helicopter has vertical takeoff and landing and aerial hover