Another new feature of upcoming INAV 1.6 (BTW, INAV 1.6 ALPHA-1 has just been released) is brand new PID controller for fixed wings. I repeat: this new controller is used only on fixed wings, multirotors are not affected.
So, what is new about this new PID controller? First of all, it is no longer a PID (Proportional, Integral, Derivative). It is a PIFF (Proportional, Integral, Feed Forward) controller. What is the difference?
Traditional PID controller computes error between setpoint and measurement and feeds it to 3 modules: P, I and D.