I want to add this discussion to record experiences in flight test from 2.0.38 and on mainly in RTL, LOITER and AUTO. Also to analise the effect of the WIND, that for me is THE big problem. I´ve tested several days my copter in different wind conditions. Below is a summary of my conclussions.
RTL flight tests
We can say that RTL works, but depending on wind conditions and direction of the wind in the moment of RTL.
Upwind. This is the best situation. The copter aproaches slowly the goal in a straight way more or less ( the goal is closed to the cross of roads in the images)
wind = 10 knots SSW
(log 21 file 1)
Below is other succesfull RTL, but the path took one complete turn to reach the goal probably due to the wind
NON SUCCESFULL TESTS
In all this test the copter diverged strongly and it was recovered THANKS to the SIMPLE mode, that is essential to survive to big crashes.
Below is a tipical divergence. It starts downwind and then enter in a divergent spiral. (Red curve shows the final SIMPLE mode to save the copter).
Other problem that happens to me is the delay in reacting once the SIMPLE mode is activated to save the situation. The yellow curve shows when SIMPLE is activated but it responded some seconds later.
Upwind RTL. Another example of bad path to reach the goal