Can't arm and motors won't test - APM + X8R + Taranis

I am having a lot of trouble with a custom build; I'm hoping you can help or point me to info that will solve my issue.

Firstly, I'm a complete RC newbie and after a heap of reading, I jumped in the deep end and am building a custom quad copter. The main problem is that I am not able to arm (and therefore spin the motors).

Firstly, the setup:
Frame: cinetank
ESC: Afro ESC 30Amp with SimonK
Flight Controller: APM 2.6 Flight Controller With 6M GPS For Multicopters
Motors: SunnySky V2216 1100kv
Battery: 4S
TX: FrSky TARANIS 2.4GHz Transmitter, Combo 2 Mode 2 includes X8R RX

- I have paired the x8r with the Taranis. If I plug the esc into channel 1 I can control each of the motors with the throttle.
- In Mission Planner, I am able to run the RC calibration and all sticks appear to give responses accurately (the AERT and some of the switches that I also set up).
- The GPS is accurately inputting my location and the Mission Planner shows my location correctly.
- Holding the throttle down and right does not arm. Holding either of the sticks in any corner direction does nothing.
- Disabling the pre-arm checks in Mission Planner does not allow it to arm.
- Running the CLI -> Test -> motors command does nothing (the battery is plugged in and the ESCs are beeping slowly).
- Pressing the Test Motors button in the MP software gives an error message "command was denied by the autopilot"

This is my second APM 2.6 as I thought the first one was faulty. This one also fails so less likely to be hardware.

Needless to say, this is massively frustrating as the whole of summer has passed while I was unable to work this out (and waiting for delivery of parts, etc). If you can help, this will be great - even if it is to say "chuck the APM and go with XYZ flight controller because it will work.


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  • Where is your safety switch plugged in ?
    No safety switch to press no arm
    You might be able to disable the need for the switch in the parameters not exactly sure but pretty sure
  • ola mateo 7 años mas tarde tengo el mismo problema. como tu dices esto es muy frustrante. no se si tirar la toalla y buscar otro hobby. si alguien supiera la respuesta lo agradeceria
  • No Need to chuck the FC ... there is a reason for not arming, just need to find out what it is :D

    Have you done ESC calibration?

    Are the trims on the Taranis centered?

    Is you Taranis in mode 2 (left stick throttle) ?

    • Hi Johan,

      My Taranis is in Mode 2 with the throttle on the left. I realised while writing this the EPROM was wiped at one point and the Inputs were different to the Mixes. I have now made both the inputs and mixes to be RETA.

      The trims are all saying "trim center".

      The ESC calibration fails.

      I follow the ESC calibration instructions on and do not get the same responses they say I should expect.

      Starting with "all at once", I get to step 6. It says "the regular number of beeps indicating your battery’s cell count" I am using a 4S battery and when plugging it in, it beeps 3 times rising, do ra me, then a long beep (maybe that IS the 4 they mean?). Then every 4 seconds, each ESC gives a long beep.

      Then at #7, I pull throttle to minimum. However I don't hear a tone from the ESCs (step 8) and raising the throttle doesn't let them spin (#9).

      I then attempted a manual ESC config.

      I plugged each into the rx, channel 1 for my throttle. I turned on the tx, set the throttle to max, then plugged in the lipo. 2 short beeps and a long beep. Then I set the throttle to min (no response) then back up to max and the motor spins. I repeat this for each motor and make each spin with the throttle.

      As a newbie, this appears like the tx, rx and ESC are working but the FC is not. Is that a valid appraisal?

      I have read elsewhere that I need to check radio calibration. I have again done this in Mission Planner. The inputs are registering as 990-2014 (+ or -1).

      I get a verbal and visual warning in mission planner, "PreArm: Check FS_THR_VALUE"

      Any suggestions?

      • An hour or so after posting, I had partial success. I can now arm (which was the main question of this thread) but I think things are still wonky.

        When writing the reply to Johann above, I noticed my radio calibration inputs were 990 minimum. In Mission Planner, I went to X, Y, Z.

        Current value of FS_THR_VALUE was set to 1000. Other options were 925 or 1100. Because my Taranis is sending 990 as its minimum, it was always below the safety threshold. I changed it to 925, wrote params and it arms...

        ... when I hold the left stick down and the right stick to the right :)  

        The motors spin and giving it throttle makes them spin fast - after months of frustration, it's a beautiful sight!

        Then to disarm it and turn them off, I put the left stick down and to the left. Yes, I use both sticks to arm and only the left to disarm. 

        (Reiterating, I'm a newbie and this is my first build.)

        Can someone please tell me which control inputs/mixers should be on which sticks?

        My left stick is, what I would call the throttle because it stays where you leave it. The right stick always centers itself. What two things should the left do vs the 2 that the right stick does?


      • Are you sure your throttle channel on the RX is connected to the correct pins on the APM and that the pins on the APM is the plugged in the right way around?

        • I suspect the pins are right, but I'm not sure.

          I have plugged the x8r into the apm 2.6 with 10 single JST cables. They are all coloured individually and I've plugged 1 on the rx to 1 on the apm, all the way to 8. Then I've plugged 2 others from a positive on the rx to a positive on the apm and likewise another from the neg to the neg.

          I've checked them again that I haven't crossed them. But because they are individual cables I could swap them.

          I suspect, however, that I've messed up the Taranis settings. I plugged it in once to the computer and successfully read and wrote the settings but I didn't close it somehow and the Taranis then showed an big warning about eprom failure and it formatted it - so I guess it did a factory wipe for safety. That was when I first noticed the inputs and mixers were different and I now assume other things are messed up there.

          How does one correctly disconnect the Taranis after writing settings?

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