I just programmed what I think you want on my 28X.
I have Rudder set to Channel 4 with its default trimmer. Don't touch this
default setup for Rudder. Do not assign the nosewheel servo channel to Channel 4.
I set the nose-wheel servo channel 10, but could use another free channel.
I chose to use trimmer switch 'B' to trim the Rudder servo and Nose-wheel servo.
The end result is:
I can trim the Rudder servo with the default rudder trim and it has no effect on the
Ch10 nose-wheel trim, or I can trim the Nose-wheel servo (CH10) with no effect on rudder trim.
After set up the Rudder stick moves the rudder servo and nosewheel servo. (Which is what I assume you want)
Here is what I did.
1. System >> Xbus >> Set Mode A
2. Trim Input Switch
Select TIS00 >> Direct >> Input B
(I chose trim switch 'B' to trim the nose-wheel servo)
3. Channel Settings >> CH10 >> Input 'B'
I am assuming the Nose-wheel Servo is Channel 10, but could be another channel)
4. Hardware Settings >> Select 'B'
Select Input Type 'GAIN' and Step 1%
5. Program Mix
Mix Rudder (Master) to Channel 10 (Slave)
(a) Master Setting
set FUNCTION >> RUDDER
Include >> Uncheck 'TRIM'
(b) Slave Setting
Change 'FUNCTION' to 'CHANNEL'
Select 'CH10'
(c) Go back to top page under Program Mix
Click on Rudder
Change NORMAL to CURVE
Then get new screen and make sure RUDDER is selected
For left rudder INPUT -150, set OUTPUT to -50
For right rudder INPUT +150 set OUTPUT to +50
(the values of -50 and +50 are arbitrary and you can modify these later to suit
personal taste. You may need to reverse depending on your setup)
I suggest trying this and confirming the actions by looking on the MONITOR screen.
You can change the Nosewheel servo deflections by changing the -50 and +50 values;
I found it is better not to use too much nose-wheel deflection. You would I assume taxi on the ground by moving the
rudder stick.
If you still have trouble I could email my model setup for this and you could then copy it to
the SD card in your 28X. Have not done that before but it should work.
.