Servos jittery and getting hot when using servo_function 5 and/or 6

I am using a Pixhawk 2.4.8 flashed with arduplane version 4.6 for a plane project. I want to use servo5_function for right aileron and servo6_function for front wheel steering. From my reading I am sure I followed what is written in the documentation, i.e. one can define the same input twice if needed. Both aileron right and steering servos function correctly but seem very distressed by jittering or buzzing constantly when the FC is armed. I would prefer to not use Y leads and in the case of steering a servo reverser as well.

Thank you

This is an addendum to my first post, I hope it makes sense. Advice would be appreciated on my post of 3 days ago. I have done further investigation which may shed some light on the situation. First of all I flashed the flight controller with the latest version, 4.1.7. Unfortunately this did not solve the problem. Some careful electronic measurements showed the SERVO1 to 4 _FUNCTION run at 50Hz and 5 to 8 run at 400 Hz. Under ADVANCED, I checked the default servo frequency, and while it was already 50 Hz, I saved this parameter again but it made no difference. Diving further into the ADVANCED parameter list without guidance is a step to far for me as I might unintentionally change some setting I have no clue about causing even more problems. Any hints on where the per-channel servo frequency parameters can be found? As I understand it the 400Hz relates to ESCs on multirotors, but the FC is flashed with plane firmware and not used for motor control.
PS I have received a reply, many thanks Axel’s DIY. I had already tried your suggestion before I posted the first one. I am sure we will eventually find what is wrong, remember I am using a later version than you would have used six or seven months ago.

Just wondering, did you accidentally enable any of the quadplane VTOL stuff?

Thanks, to be 100% blunt I would not have an idea. I don’t think so, I have been around the hobby for a long time so I am usually careful and not play around. I have a tailsitter and maybe the new project has been COVID. I am at a loss so it may have to be Y leads not my preferred option. I can get around the problem by advancing the trim by about 50% again not a good solution.

Thanks agin

For some troubleshooting try to set it to manual mode and see if the servos are still twitching. That will just rule out if it’s control issue or not.

Thanks for taking the time Allister, I have made all tests and measurements in manual flight mode. I suspect that maybe something is astray with my FC i.e. PX4PILOT. I will also try one of my Pixhawk 2.4.8 ones. Further I will a reset on the PX4PILOT and flash the firmware and see if any parameters form it previous use as a FC for a quadcopter are causing my problems.

Thanks to the resopndees, the problem has been solved. Chris Friesen set me on the path of success, I looked up the Q_ENABLE PARAMETER which was set at 2 (VTOL enabled) resetting it to 0 soon fixed my issue. I have no Idea how it became 2 the the FC has only been used for a hexacopter, maybe (I have never looked) it is the default value. I assumed that when new firmware is flashed changing from one type to another the correct parameters will be written. It has been an interesting week to solve a small problem but the is that not what aero modelling is all about.

BTW is there a frimware file available that one could flash that leaves the FC in a pristine as new condition? I have use ROVER in the past.

When you flash another type of ArduPilot firmware that will reset all the parameters. For example if you have Plane, then flash copter or rover, then back to plane and it will all be reset like new.