On an APM (8-bit) with ArduPlane V3.4.0 (c1fc5a44)
Using rudder to arm the plane does not work. There are no error messages, and arming disarming works without issues from Mission Planner. I have a Pixhawk with V3.5.3 and it works as it should
APM arming parameters.
One thing I noticed is that parameter BRD_SAFETYENABLE does not exist, but on the git changelog it says it was added in V3.0