Hello. I'm trying to make a helicopter, but the main problem I'm having is the helicopter keeps yawing to the left or right (depending on the direction the main rotor is turning in) when it lifts-off.

Also, when I'm trying to fly it, the yaw won't let the helicopter stay still, it will always want to turn.

Any ideas?

(p.s. I can leave an image of the helicopter if necessary)