Hi everyone,
AFAIK ArduCopter can tune PIDs autonomously. Do you think that it will be feasible to design such autonomous autotune process in ArduPlane? Once we know the enviroment, It must be ok right?
Secondly, When do I need to start considering retuning? For example, If I put more weight on the vehicle it might start being less responsive? So that I need to tune again.
Thanks in advance.
Check out this part of the documentation. In general, small changes do not have a big impact on the dynamics of an aircraft. Only by doing the math to estimate the stability derivatives will you have a hunch if the change is significant enough for a re-tune.
https://ardupilot.org/plane/docs/automatic-tuning-with-autotune.html
Already read the documentation. What is the related math to estimate the stability? I am a noob. Sorry 
You can find ways of estimating the stability from books by Nelson, McCormick, Beard&McClain, and Stevens&Lewis. There is also the USAF DATCOM (also used in Matlab, Digital DATCOM). The gist is that if you have set up the plane with the CG in the correct spot and you haven’t added a significant amount of weight at wing tips or something similar, you’re probably good. You can learn a lot about how planes behave in the air from reading though.
Thank you for you reply. I will check them out. But what I understood is, If you place the weight such a way that does not affect the center of gravity, it would be OK, right? Or making aircraft heavier will result it to be less responsive or sluggish, directly?
Yep! That’s the best place to add weight. Just need to fly with more lift.