When I switch into RTL mode APM immediately cuts my throttle to zero.  My Sky Fun Jet does a beautiful job of gliding back to launch and circling, but the throttle never comes back on.  I am guessing that APM cuts the throttle to descend, but shouldn't it power back up before reaching the ground?  It's almost as if the commanded altitude is below ground level.  Perhaps my cruise airspeed is set t…