FAA Assembly & Rigging Practice Test

Using a pair of counter-rotating rotors is effective in preventing torque from affecting the flight of helicopters because it balances the forces generated by each rotor. In a conventional helicopter with a single main rotor, torque is produced in the opposite direction of rotor spin, which creates a need for a counteracting force to maintain stable flight.

Counter-rotating rotors work by having two rotors spin in opposite directions, effectively canceling out the torque created by each rotor. This design reduces the need for a tail rotor, which is typically used to counteract the rotational forces in single-rotor systems. By eliminating or significantly reducing the torque-related issues, helicopters with counter-rotating rotors can achieve better stability and control in flight, enhancing overall performance and safety.

In contrast to this correct approach, other options, such as adding weight to the tail or adjusting the tail rotor's pitch, primarily serve to counterbalance the torque rather than eliminate the root cause. Increasing rotor RPM can increase lift but may also exacerbate torque effects and complicate control, which does not directly address the torque problem.