POS HOLD shooted the drone to the sky

Hey all,

I am here to request your help. I hope this is the right forum for this.

I have been trying to fly my drone, and I triggered POS HOLD, but the drone shot to the sky and then fly out of range, after that, I panicked and crashed the drone. Could you help me to understand what happened?

I attached the flight log. (edited correct file)

Best Regards and fly safe,

The right thread would be the version of Arducopter you are running which is 3.6. But that log doesn’t really show what you are describing. It was only in AltHold for one instance and the barometer shows it didn’t leave the ground at that point.In fact by this log it didn’t change altitude by more than a few meters at any time. Several of your Flight Mode changes were refused because you did not have GPS lock. Describe this craft and the components on it.


My apologies, I believe I uploaded wrong log here is the correct one.

I have F450 quod copter with navio2 + rasp

After you switched to PosHold you can see what you are describing. I don’t see a definitive answer as to why. Z-vibes are a bit high but very few clipping events. Tuning is poor but you are on default parameters and haven’t followed the basic tuning guidelines for the craft so no surprise. Hover thrust from learning was increasing rapidly during the ascent so maybe it was too low to start with.

Thanks Dave,

Should the next steps then be to do the basic tuning guideline and not to engage pos hold too low?

Yes on the tuning step here:
Depending on the size of the craft some of the parameters are critical. Any reason you are not using current Stable (V4.0.3)?

On PosHold I’m not sure what happened there. I can see you dropped the throttle yet it rapidly climbed but can’t tell why.

Your accelerometer either got loose, or went bad. It shows readings all around which made EKF crazy and believe that it is sinking, therefore the command to raise altitude. eventually the EKF detected the faulty situation and initiated failsafe and land, but then you switched back to stab and crash.

Tanks for the reply! Just a quick question, are you suspecting that something could be broken? I was thinking also that I was flying it too low.

I think it was broken.

Hello again,

I hope you are doing well.

I made some necessary tuning, which made the copter fly smoothly on stabilized mode. Then I attached the drone to rope just in case and tried alt hold again and tried ALT HOLD with the same results where the drone climbs uncontrolled. Here are two logs of two different flights where this happens:

Are there some calibration things I should still do, or is there a way I could test the sensors before accepting that I need to buy a new navio2 board (I have to admit I crashed it quite a few times)?

Thank you for your help,

The accelerometer data on Z axis does not make sense at all. It constantly shows less than 9.8m/s/s which indicates that the copter going down. The EKF vertical speed calculation shows constant descent because of this. And this is the cause why copter shooted to the sky when you switched to alt/pos hold.
I would say it is a faulty accelerometer (unfortunately you have only one onboard, so there is no reference). But this only my opinion…

Should I also get values lower than -10? If so, would it mean that it detects only one direction of movement?

Vertical acceleration generally relates to Z axis vibes and you have identified an anomaly with it not showing as much -ve travel as positive.

Is something hitting the board?
Especially on acceleration up?

It is probably worth doing a full accelerometer calibration and seeing how the range looks after that.
Motor3 output is higher than the rest so make sure your craft is balanced and hang the rope from the centre

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Yepp. This is how it should look like normally

Hey Mike,

Nothing is hitting the board. It is a basic F450. One thing that came up to my mind is that I do not have vibration dampening.

I do full accelerometer calibration. I was flying this drone close to the railroad, could it affect the performance?

Nope, I do believe that your board is toast.

I ordered a new one. I let you know how it goes.

Hello again,

I attached a sponge to my FC to dampen the vibration. Could you please check the log one more time and comment what do you think?

Here is the log:

It definitely improved the situation, you should give it a try for poshold…

That is excellent news, thanks! I will do it tomorrow!