Changes

Torque should be at least 2-3 times the heli weight. Speed should be at least 0.1s/45° or even faster. In addition the servo should be very precise, have little backlash and a low deadband. And of course best would be if it is a digital servo and supports 200 Hz driving frequency. Also using a special heli servo which are specially made for maximum vibration resistance is a good choice.

Servo torque in kg/cm should be at least 2-3 times the heli weight (in kilogram). Speed should be at least 0.1s/45° or even faster. In addition the servo should be very precise, have little backlash and a low deadband. And of course best would be if it is a digital servo and supports 200 Hz driving frequency. Also using special heli servos which are designed for maximum vibration resistance is a good choice.