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 to low (10 ft/s) and the throttle is cut in an effort to slow down?   I bumped it up to 15 ft/s but have not had a chance to try flying again yet. Any suggestions?

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Yes, the throttle should come back on when the aircraft is at the requested altitude and speed. Your cruise airspeed is indeed very low for a Skyfun. I'd set it to at least 3x that, and ideally 5x.
Chris, thanks once again for your help. Am I correct in thinking that the RTL altitude is set "automatically" to some value above the launch altitude, and that I shouldn't have to worry about setting it somehow? As for the cruise airspeed, I bumped that up in my APM_config.h file. Per your suggestion, I will increase it even more.
Default altitude is set in the Mission Planner:

So this altitude gets applied in RTL mode as well as Auto mode. I was not aware of that. And if I remember right, the units in this box are meters?
Guys, I too am having this problem and I would appreciate any advice.


When ever I switch to Auto my motor switches off completely, it does an wonderful job of keeping the plane stable and trying to get to its waypoints, but doesn’t get very far due to no power.


I've tried setting the Airspeed m/s higher in the AMP PID config and tested on the ground, but not had any luck.


I would really appreciate any help or pointing in the right direction.



Might be any number of things, including a reversed throttle channel and accidentally setting altitude to zero.

Did you do a radio setup in the CLI?

Does it work in RTL mode?

Hi Chris


Yes, have performed the radio setup in the CLI and seems to be ok, would you like to see the results?


It doesn't work in the RTL mode either. I have also reversed the throttle channel and no change.


I ran the Radio test in the CLI and I can see in "in channel 3" the data moving up and down, how ever on the "out channel 3" I see 0 until I get to mid throttle then 100 at mid throttle then going past mid throttle it goes back to 0. The results are reversed if I disable throttle reversed, so it goes 100 - 0 - 100. Does that indicate to you that there is an issue? or is that normal output data?




That is not normal output.  Try the radio setup in CLI again and make sure you cycle the throttle stick through its full range.

Thanks Doug, I didn't think it was normal.


I have have been through the Radio setup in the CLI and i'm still getting the same output.


Any ideas?



when i switch to RTL, my throttle cuts to zero and the aircraft does a right turn to come home. default alt is set to 50, but the airplane glides well below that. i need to go back to manual mode to recover. home location and mouse location altitudes are at zero in APM planner.


Stabilization mode works perfect today. flew the HawkSky today in 10+ winds.



checked my flight logs for today and im seeing altitude of 1992 which it way too high. this would make sense that the APM makes the plane descend and cuts power, but why is my altitude reading so off?



Strange mixer or other setting on your TX?


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