Rudder_Only mode seems not needed, and not desirable for VTOL

ArduPlane Plane 4.6
1

I have a VTOL vehicle with wing but no ailerons - planning to use Rudder plus dihedral for roll control.

I initially set RUDDER_ONLY to enabled. However, nasty surprise, in the hover (Q modes) I had no independent yaw control. Lateral (roll) inputs went straight to yaw! Without a script, there is no way to turn of RUDDER_ONLY in the hover/Q modes, but retain it for forward flight modes.

But, it doesn’t seem that it is needed for the following reason:

Setting KFF_RDDRMIX (Amount of rudder to add during aileron movement) to 1 means that any aileron commands are duplicated in a rudder command… 1 to 1

…which is exactly what Rudder_Only does?

In summary then, setting KFF_RDDRMIX = 1 makes RUDDER_ONLY redundant (and gives me the control of yaw in hover).

Am I messing anything? Seems like I might be…

2

I’m curious, were you able to get it to work with a script?

I don’t think you’re missing anything. I wonder if you may have hit an edge case that wasn’t accounted for.

3

I havent tried the script route @Allister, since it doesnt seem like I need rudder_only at all. I have realised that manual/acro etc DO need rudder_only to be set, as I dont think KFF_RDDRMIX is active in those manual modes. But since I wont be using those modes, it seems using KFF_RDDRMIX to effect roll control via rudder is simplest.

Curious though - if I didnt have the Q mode problem, and I did use RUDDER_ONLY, why does the guidance say “You should also set KFF_RDDRMIX to 1.0” - seems like duplication?