I am using the GY401 on a Hangar 9 Twist with the medium-torque Futaba digital S3050 servo on the rudder and it works great. Also, I am using a 7CAP airplane transmitter.

My settings: Switch E mapped to Channel 7
Sub trim and Dual rates on the rudder channel 4 are 0% and 100% respectively.
Set the End point adjustment on Channel 7 on the left to be 75% and 1% on the right.
Set the travel limit using the gyro pot and not the end point or dual rate setting. In other words, if the rudder needs to move another 10 degrees at full transmitter deflection, turn the little travel limit gyro pot to get what you want.

The heading hold mode is Switch E on and always turn on the transmitter with HH mode on. Don't move the airplane for 3-4 seconds to let the gyro initialize. If you can see the gyro the solid red LED is on when in HH mode. Then, turn off HH mode by switching switch E. Carry the plane to the flight line and, when it's lined up with the runway heading you want, switch back to HH mode and wait 3-4 seconds while the gyro initializes. Then move the rudder stick back and forth a couple of times and then center it. Don't forget this last step or the rudder may have an offset.

After takeoff (or if you get into trouble) turn switch E off and you are back to regular rudder control.

What I use the gyro for is on rudder for 3d Hovering and torque rolls. I take off in with switch E off and turn it on in flight when I'm ready for some 3D. Then I move the rudder back and forth a couple of times before going vertical and center the aircraft. This enables me to concentrate on engine, ailerons and elevator without having to worry too much about the rudder. When it falls out or I end the manuever I effectively turn off the gyro by switching switch E to off. By effectively I mean turning the rate gyro part off because I only have 1% gain set in the end point adjustment for channel 7.

How I learned to do this was I built a small rudder and horizontal stab on a piece of 1/4" plywood and experimented. Before you fly make sure that Switch E turns off the gyro and turn the plane to ensure rudder only moves when commanded by the transmitter and centers when you are hands off. When the switch is on make sure the rudder turns in the direction of the turn (or more accurately a left turn generates a right turn rudder position). Also, with switch E on, the rudder will not go back to neutral until the plane returns to the start position or you move the rudder back to neutral with the transmitter.

Works great and you don't need the S9254 expensive servo on an airplane. In fact you can use a non-digital servo but remember to switch DS (digital servo) off on the Gyro or, according to the manual, you will ruin your non-digital servo.

Good Luck!
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