I have a question on using TX mixing, for example when used to compensate for pitch change on deployment of flaps.
When setting up a plane in manual mode, I found that flaps have an effect on pitch (quite normal) so I dialed in some up elevator to compensate. However, what happens if I deploy the flaps in an assisted mode such as FBWA or Stabilize? Would this not cause the plane to nose up more than necessary, because the flight controller is will already compensate for pitch change caused by the flaps when the sticks are in neutral position?
I could go and test this, but thought I would ask here first.
Hi Jacques,
If you have a Flight controller, ideally you want the mixing onboard the FC.
The mixing on ArduPilot is pretty limited. If you have a Pixhawk/pixracer /pixfalxcon or other similar PX4 hardware, then there is a custom mixing option, which basically involves writing a .mix file onto the SD card, called APM/CUSTOM.MIX
There is some info about how the px4 mixing works here http://dev.px4.io/concept-mixing.html#px4-mixer-definitions
However I find that far from ideal, so I did start work on an alternative which uses a more programming language approach https://github.com/kwikius/mixer_lang/blob/master/glider.mix
It will also be able to read ArduPilot eeprom parameters, so you can change parameters on the fly
However that is not yet implemented in ArduPilot
I would suggest modifying the mix on your transmitter to only apply that mix when the mode switch is in a manual mode. It makes the mistake programming a lot more convoluted. But it would prevent the problem you correctly forsee.