"I must admit that I am also having issues with APM Planner and communications with the last version.
2 different computers, 2 different copters and the link keeps randomly dropping out.
Maybe this is the issue and not the APM after all."
"OK, a couple of things to check.
Idle speed parameter set in the APM, just checking that even if you set it to off as soon as the throttle is raised to 4.5% the motors jump to ~20%.
Do you have ANY sort of throttle curve set up in the Tx?
"OK, so if you were connected to Mission Planner then you would see in the 'Initial Setup' the frame type window which would have a highlighted radio button beside the frame type you have selected.
Have you seen this?
The 'x' or…"