RE: Does gyro on rudder work against aileron?
There seems to be some major misconceptions about what a yaw gyro does, in particular a belief amongst some of you that it will balance turns. It will do no such thing, indeed in many cases a yaw gyro will try to put the model out of balanced flight, and keep it out of balanced flight.
Imagine your model flying along, in balance. You add left rudder to skid the model left. You release the rudder. The fin tries to yaw the model to the right, back into the airflow. The yaw gyro senses this and applies left rudder to stop it. So the gyro tries to prevent a return to balanced flight. Now add a little bit of left bank. The model starts to slip to the left and the fin tries to yaw the model so that it is pointing into the new direction of travel. That is a turn, wings change the direction of travel and a combination of yaw and pitch change the direction of pointing. As soon as the model starts to yaw to point the same way it is going, the yaw gyro senses this and applies opposite rudder. It thus tries to put any turn out of balance. Next imagine being hit by a gust from the left. The model should yaw slightly to the left to keep the airflow head on. That would keep the slip ball or yaw string centred, and thus in balanced flight. But the yaw gyro will try to stop that, resulting in the gust causing a sideways acceleration which will be shown by the slip ball or yaw string moving away from centre, thus once again the yaw gyro is causing unbalanced flight.
Why should it try to unbalance the flight? Simply because it is not designed to balance the flight! Balance is matching the angle of bank to the resultant of the 2 translational accelerations of gravity and any horizontal motion in the plane of the lateral axis. A gyro is an angular motion sensor. An angular motion sensor can’t sense translational effects, can’t sense accelerations, can’t sense angle of bank. Since a gyro can’t sense any of the requirements of balanced flight, it is not going to create balanced flight.
Since the yaw gyro will try to yaw the model out of the turn, and swept wings have a strong dihedral effect, the yaw gyro will have the secondary effect of reducing the roll rate and even trying to level up the model. Therefore you need to use the lowest gain that is required to stop the fishtailing, or to reduce it to an acceptable level. A higher gain is wasteful and increases the unwanted effects.