Translations:Help:FAQ:Setup/6/en
I cannot get any servo horn arm to be mechanically 90° to the boom. The AR7200BX/AR7300BX does not have a tail "sub-trim" feature!? Is trimming in the transmitter allowed?
Do not trim the rudder servo by using the transmitter as this will apply a constant rotation command to the unit! When you can't get the servo horn exactly 90 degrees this has no significant effect. The "90 degrees rule" only should give some good basis for initial linkage adjustment. In flight the system will control the servo all the time anyway, so it is not an issue if the center position is slightly offset.
It is more important, that the tail servo linkage is in general adjusted correctly, so that you get asymmetric tail pitch throw: 40 degrees against main rotor torque direction, approx. 6 degrees at center position and 20 degrees in main rotor torque direction.
When you've updated your AR7210BX to firmware version 5.x.x you can trim the rudder servo by software from the StudioXm App or on the device in Quick trim menu (PARMETER MENU point A). This can be useful when flying with the tail gyro set to "Rate-Mode" because here the gyro only dampens sudden movements but does not hold the tail in position all the time.