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。

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It is a good practice to check the bolts and nuts on the main rotor head and tail rotor after every flight.

每次飞完检查主旋翼头和尾旋翼头的螺丝螺母是一个很好的习惯。

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It included the black box flight recorder, the fuselage with the engines and rotor gearbox attached, the separated rotor head with the main rotor blades still attached, and the separated tail.

BBC: Crash report urges safety checks