How is precession overcome?

• A. Increasing The Main Rotor RPM
• B. Offsetting The Linkage In The Cyclic Pitch Control System To Create An Input 90 Degrees Ahead Of The Desired Action
• C. Reducing Blade Twist At The Root
• D. Anti-Torque/Tail Rotor Thrust

Answer: (B)

Gyroscopic precession means that when you command a change in the rotor plane in one direction, the rotor tends to respond 90 degrees later. To make the rotor tilt in the direction you intend, the cyclic input must be applied a bit ahead of the desired motion. This lead is achieved by offsetting the linkage in the cyclic pitch control system so the blade pitch changes 90 degrees ahead of the action you want. In other words, the control system is phased to produce the correct tilt despite the gyroscopic delay.

Increasing main rotor RPM would not fix precession; in fact, it can amplify the gyroscopic effect. Reducing blade twist at the root changes aerodynamics but not the timing of the gyroscopic response. Anti-torque/tail rotor thrust deals with yaw and torque balance, not the cyclic timing issue.