I am having trouble getting some questions answered wrt RTL Fail Safe and need some help.
1. What is an effective way to test the Fail Safe on the ground?
a. How to be sure the motor will engage at the proper RPM to keep the plane airborne during RTL?
b. What setting(s) govern the motor RPM?
c. What is the dominate feedback loop for motor RPM? With and without Airspeed sensor
If I missed it in the Wiki, I apologize but I think I scoured it pretty good. The Fail Self set up and testing, IMHO, deserves to be addressed in more detail.
I'm sure the Dev Team can give you a better answer, but basically you can't test the motor speed on the ground.
As long as you have a GPS lock you should be able to see the APM switch to RTL mode on the ground (I think), but to "test" the motor you're going to need to be in the air. The motor speed will depend on things like if you're above or below your set RTL altitude. Trust the APM, it really does work well. The best way to test it is to engage RTL when the plane is only a short distance away, and be ready to switch back to manual if something goes wrong. If you have tested Stab and FBW modes beforehand then you shouldn't have any trouble with RTL.
Thank you. Yes, I can see, via telem, that the APM goes into FS. The motor does nothing and that is probably by design for safety. However, I still worry that the motor will not come up to speed. On my other OSD's with RTL, one sets the "cruise" throttle. The APM must use an algorithm to do this based on altitude and GPS speed and Airspeed if you have that enabled. I would just like to know more for peace of mind. Many OSD sites are replete with crashes caused by RTL and Fail Safe. In fact, I think there is a MyGeekShow test of the APM2 where it momentarily behaved as if it was not going to come home.