Hello all,

I have had no luck whatever with getting throttle failsafe to work. I have set up the config file to: THROTTLE_FAILSAFE 1, THROTTLE_FS-VALUE 920 (my radio throttle drops out at around 935) and FAILSAFE_ACTION 1. It is difficult to ground test this but in the air by collapsing the antenna on my 72Mhz radio the plane quits running and the control surfaces go nuts. I have regained control by extending the antenna again a couple of times I crashed, I hate it when that happens. The plane showed no tendency to turn and head home. I have been using version 2.7.1.

Any ideas?


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Hi David,


Sorry for another post, now I see that you use the Red board or the 328.  Would you mind sharing your APM_Config.h file?


Best wishes,



Hi Peter,


Sure I'd be happy to share it. I have changed it a lot with different changes and even loaded the stock one just to test things out. The one I am currently trying is nearly stock. I have been having troubles with range for awhile and my system gets the jitters and will even go through the reboot cycle at very close range. I am not going to use it on my plane until I get this solved. The plane has crashed a few times and although everything seems fine I think there might be a hardware trouble. Perhaps I overloaded the MUX. Working with it  I have spent a lot of flights just testing the different modes minus take off and landing. I get nervous when the plane is on auto and flying nearly out of view until I see that wing go up into a bank as the plane heads off to it's next waypoint. You can see my concern about the failsafe system when I am havimg range problems. I want it to fly its butt back home pronto!

I haven't used any other system out there but am impressed with the effort DIY  is making toward these toys. I am using the IMU instead of thermopiles and feel it does a great job of guidance plus smoothing plane performance.  As well as a drone I want to use it as a fly by wire for my FPV plane to ease the control load. It performes very well in this capacity although Birdseye view sells a stabilizing unit for $105 that I am sure works well and is a dedicated system.

If I can't fix the range trouble I may order the Birdseye view unit or order a new AP kit and start over. Tough call at this point. I seem to be the only person having this issue. Here is the AP_Config file. I just sent this reply and don't see the file attachment so if it does not show up I can copy and print it for you.

I do not have the internet every day so could be a few days to respond.



If your throttle failsafe value is 920, but your radio only drops to 935 when it looses signal then you will not go in to failsafe.  You need to have the failsafe value set below your normal low throttle value but above the value your receiver will output on loss of signal.

Hi David,


My APM_Config.h is almost original.  I only modified GPS, GCS information.  Are you using 2.7 or 2.8? 




Hi Peter,

I am using the ver 2.7.1 code for the version 2 four channel unit produced by sparkfun with the IMU.

Hello Doug,

My mininum throttle value by the serial debug feature is 935 at close range so if set to 920 I presume the failsafe should start at any signal value lower than this. I would be gliding at this point and perhaps getting out of range or I just turned off the radio to test. That would definitly lower the pwm of all the inputs to the receiver. The receiver would then be left to its own devices, perhaps spitting out all manner of signal. Of course the AP will go nuts under these circumstances but it really shouldn't. The unit should react in a logical fashion. If a failsafe is called for then the plane should RTL and Circle until the transmitter is switched back on, right? No really, right? Or at least moderate a crazy input signal somewhat and set all control surfaces to neutral and shut down throttle. 

Maybe the signal pwm changes with an increase in range but there is no doplar effect going on with range. If I am listening to the radio and get out of range it fades in and out and then I loose it. Otherwise I hear the music.

To test I have actually set my minimum failsafe value to 950 and decreased the throttle to below this or throttle off with Fly_By_Wire_A and the plane acts pretty much as I would expect by throttling up on it's own and a slight change of rudder as if attempting to RTL while on the bench.

It's really all about the range and I can only back up about 60ft before getting out of range with AP installed now, antenna up. It is a puzzle. I should have been a Beta tester ;-)


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