Quad APM2.5 / 2.9.1b it Disarmed (reset?) itfself at 80m alt when it was in Auto mode, hovering position

Quadcopter, APM2.5, Arducopter 2.9.1b.

During an Auto flight mode (with hovering on a fix position), it crashs down uncontrolable from 80m altitude. I did repeat this mission many times before, never such problem.

When I look at log/tlog files(atatched), I noticed at the middle of the Auto mission, at 80m, it "Disarmed" for no reason.The log files shows altitude stop at 80m, throttle stops at medium value.

It looks for me APM2.5 was reset in middle of the flight. Could someone confirm this?

Battery was at 64%, no errors in log file.

What could be the reason for this? It scares me a lot.

PLEASE, I need to find why happened.



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Anyone knows why Arducopter 2.9.2b Disarmed itself at 80m altitude in Auto mode and then crashed down?
It really concern me.
Logs are provided.

Something very odd is going on in the log for Vcc status...


None of it makes sense to me as the normal value should be 4.9 to 5.1 or so. It doesn't look like it was even close until the very end of the log.

What is your APM power source?


Hi Doug, thanks a lot for your reply.

I am using APM Power Module with Deans Connectors which comes with the new APM2.5 from 3DR.

Indeed, it looks for me also as something strange happened. Effectively all motors stops abruptly and quad felt down from sky.

Could you please give me an example how this Vcc should be as normal?

What would be the cause for that? Is an issue with APM2.5 or with APM power module?

Hi Guys,

My VCC look like that since the upgrade to 2.9.1 I have however had no problems at all with this firmware.

I would like to know why the APM displays it like that though.

I am also using the power module from 3dR with the jumper removed and another power source on the output rail.

I still have by chance my old logs from the APM2.0 with 2.8.1.  When I look at the Vcc, the value is like a horizontal line, very few fluctuation.

Is that related to APM version or to Arducopter version?

As Doug said, the normal value should be 4.9 to 5.1. Why it shows 0 values many times?

Andreas, could you please post an image with the Vcc value from your APM? Please use the APM power module with battery as a power, not the USB power.


I have found one. This is setting up the camera gimbal in my office, so no flying. The copter is however powered by the battery and not the USB.

Flying logs look like the one above.

I would really like to know whats going on here.

I have 2.9.1 on all 3 of my quads, and they all look like that.

here we go!


Your Vcc is almost 0zero. Weird for me.

I am not sure how to interpret this graph, maybe you can help me.

I can't help unfortunately. i will get one of the flight logs off my Laptop and post that tomorrow. Maybe Randy or one of the developers can shed some light on this.

All three my copter fly like they should even over prolonged periods of time.

Look here https://vimeo.com/63302808

Hi Tim, thanks for your reply.

Indeed, I did enable RAW and Motors because this is a new APM2.5 and is on testing.

However, there was just 4 logs on that APM, not more, usually I delete the logs from APM once per week.

But I did have many situations where with RAW and Motors enabled I did have many (>20) logs and never had a similar issue.

Do you believe this could be the real cause? Should I check something else? The battery on the log was at 64% when issue occured.

And I am wondering why Disarmed was toggled at this altitude? I did ready in other recent posts where the flight mode was changed itself by APM, not sure is the case here.

I can try to fly again after fixing (motors, arms, props broken...), sure I will do, but I need to see where to focus.

Should I use a separate power for APM, instead of 3DR APM power module? On APM2.0 I did not have this power module and never had an issue like this. Just wondering what to do... thanks anyway.

With the latest release of AC code 2.9.2 I would hope they devs did not mess with the Vcc monitoring routine intentionally.

Here is a dead flat Vcc from one of my old tlogs... (I think they measure the data in millivolts. 4000 = 4000mv = 4.0 V)


Life would be great if all our Vcc looked this way all the time.


Here is one from a member's tlog...a serious problem event...


I don't remember the details of their problem but they certainly had one and posted the tlog trying to understand what happened.

So, your Vcc was no where near typical and either is a result of a buggy software routine scattering the data sampled all over the place or...??? I suspect software. There is no way that copter would fly with a real Vcc as you had in your log.

If the display was in millivolts then what we see is noise and not a real representation of Vcc.

Paging software folk...


Great reply. Now there are 2 confirmations on this direction. The voltage supplied to APM was not continue or linear 4.8v to 5.0v, but as pulsing, even zero volts many times. This will help me to focus on that on next testing.

Now I am wondering if this is a APM2.5 issue or APM power module issue?

I will try to monitor this on next tests and even to use a separate APM power (as in APM2.0). This would eliminate if the cause is the APM power module, or both (APM2.5+power module).

As you said for next release 2.9.2 or higher, it would be great if the system will monitor the good level of APM power for short time interval and if this is not good, to monitor some visual warnings or audio or both.

And to raise some errors on log. Parsing my log files, I did not see any error.

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