Arducopter crash. Throttle wire fell out?

3689532010?profile=originalI was flying my hexacopter at a local school on june 22. Everything started out great. I was flying it in auto, loiter, guided, and RTL mode. While i was flying my hexacopter started drifting away because of the wind. At witch point i brought it back and tried moving the throttle down to land it, but the throttle wasn't working. I decided to flip the switch and put it into RTL mode, after that the whole thing died, the motors lost power and fell out of the sky. Im not shure exactly what happend but i think the throttle wire fell out.

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  • Moderator


    I'm not a copter guy so take this with a grain of salt because the parameter may not be the same in Arduplane code as in Arducopter code. That said the value is input in the Mission Planner when you setup Failsafe under the Hardware options menu. If you've already done that, then you can manually change the value, I believe it is in the Advanced parameters group. For me in Arduplane the parameter is called THR_FS_VALUE not FS_THR_VALUE.

    The procedure is outlined here in the Arducopter wiki.

    NOTE: The wiki refers to FS_THR_VALUE as Randy states above. So the parameter may be named differently in Arduplane code.

    Good Luck,


    Nathaniel ~KD2DEY

  • @randy where do i change the FS_THR_VALUE?

  • Developer


        Yes, the middle level sounds good.  You can see where I put the apm on my quad in this video.  I use the long stand-offs on the bottom and the shorter ones on the top (although I need to extend them as well to make enough room for the APM.

  • @randy where should i move it to then? The middle of the stacking plates? I don't want to move it to the top because I don't want it to get smashed when I crash.

  • @randy thank you so  much

  • Developer


         Thanks, I've had a look at your logs.  I think you ran into the "throttle at zero motors will go to minimum" bug. 

    Loiter/AltHold/Auto/RTL bug: if you switch into these modes with throttle at zero motors will go to minimum until you raise the throttle.

    It's mentioned in red on the original 2.9/2.9.1 release thread but not in the 2.9.1b release thread sorry!  I believe if you'd raised the throttle even just a bit after switching into ALT HOLD it would have recovered.

         In an attempt to make up for this in some small way, I've had a bit more of a look at your logs:

               1. the FS_THR_VALUE (throttle failsafe threshold) is set too low.  At 900 it will not detect when the radio loses power.  It should never be lower than 925 and of course you'll need to check that when your receiver is turned off that channel 3 falls below the failsafe value.

                2. when it comes time to move to AC3.0 you will need to move the APM up and away from the PDB, powerwires, etc because the magnetic interference is quite bad.  You can see in the graph below how the mag field (red) changes dramatically when you change the throttle (green).  It shouldn't change by more than 30%.  You'll also want to re-do the "Live Calibration" of the compass and do the compassmot procedure.


  • If you still want to see the .tlog it is in the discussion version of this Here

  • @randy I looked at my tlog and i found out what happened it was it guided mode and i had the throttle down to try to lower it. It wasn't working so i flipped it into alt hold, then it crashed. I've got to remember to learn the mixing modes and keep that gear switch down.

  • Solder as many contacts as you can, that's my golden rule. Everything else is plug and pray (esp. some T Deans).

    I am very sorry for your crash!

  • Ouch. That was a significant impact to rip the motor mount screw head out of the arm.

    You could probably repair that with some specific hammering and using a larger washer on the next screw.

    On the other hand, you might have been shipped an extra arm with a 3DR kit.

    Regardless, it doesn't look like a basket case.


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