直升机不但能向前飞行,而且还可以侧飞和垂直起落,它对起降场地的要求比一般固定翼飞机低得多,可使用的地域或范围十分广泛。但是,由于直升机很大直径的旋翼在飞行时空气阻力很大,所以飞行速度较慢;同时为驱动旋翼还需要较大的动力,发动机消耗的燃料也很多,这些都使普通直升机的航程还不是很远。 Helicopters can not only fly forward, but also can fly sideways and vertical landing, the landing ground requirements of its much lower than the average fixed-wing aircraft, can be used in a very wide area or range. However, due to large helicopter rotor diameter in flight air resistance is large, so the flight speed is slow; at the same time to drive the rotor also need more power, the engine consumes a lot of fuel, which make the average helicopter range is not far away.