The above unit makes the rotorhead movable in one direction.
上述单位，使转子头动产在一个方向。
2
Helicopters require a tail rotor to counteract the rotor torque; this and the articulated head complicate flying, construction and maintenance enormously.
需要直升机尾桨抵消转子力矩；这和阐述头复杂飞行，建造和维修极大。
3
In a helicopter the articulated head and tail rotor gearbox are required to be a very high specification design using the best materials and requiring frequent and costly maintenance.