I've been struggling to understand how to get the APM failsafe working properly and have yet to find some clear instructions that a noob like I can follow. It suddenly dawned on me how to get it all setup.
Here is my normal zero throttle output:
Here it is when the radio is off:
The AR8000 can be taught what to do if it looses contact with the mothership. The default is to leave or move the throttle to zero. As you can see, zero is normal and not enough to invoke the APM failsafe. (see here for more info on the APM Failsafe: http://code.google.com/p/arducopter/wiki/AC2_Failsafe)
What you need to do is tell the AR8000 to go below zero when the radio is lost and here's how you do it:
What you have done is told the receiver that when you loose contact, this is the new throttle position. It is of course, way lower than normal range. The low value is enough to trigger the APM failsafe which will RTL and land.
This all works in theory for me and MP seems to agree, I'll be out testing it tomorrow but just wanted to get it all down on paper so to speak.