A few users, myself included, appear to be having issues calibrating accels and/or arming when using APM 3.2 on a Pixhawk.  I see posts here and there, but thought it may be best if those having the issue could all 'check in' to one post so that the developers can see how widespread the issue is and gather data.

My Pixhawk will arm occasionally, and will even fly successfully.  Occasionally however it will not arm and I will receive the pre-arm error "Accels not healthy".  A few days ago I was able to arm and fly thorugh one lipo, then after landing and swapping batteries I could not arm due to this reason.  I have attached the logs from the successful flight, as well as the failed pre-arm logs, to this post.

As you can see from these images there is something amiss with IMU2.  This is a snippit from the good flight, showing values for AccX on IMU1 and IMU2:

and here are the same values on the second attempt, pre-arm.

In the 3.2 release thread a few users had mentioned the issue and Randy advised to set the log_bitmask to "131070" so that it will log everything including the pre-arm checks.  I encourage others having the issue to do the same and share the logs and experiences here so that we can find out what is going on here - is there a bad batch of Pixhawks in the wild that only now show the hardware errors due to something new in 3.2, or is there an issue in the APM software?

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This mini-pixhawk looks amazing. Given that Banggood are replacing my controller free of charge, do you by any chance know if this product upgrade: "added the second PMEG2005CT and 350ma ResettableFuse)"  is referring to improving the power supply to IMU2 - really hoping you might know, so I have more confidence in this replacement. Any idea?

at $65 worth a shot I guess...  


 Please log monitoring and feedback.

My second flight today, it seemed that the controller has not adhered height / mode Loiter /after the start.
I reduced the throttle to zero and disarm motors after landing.
The unit does not react and spontaneously adds gas. hexacopter flips and the engines are still running.
I have to remove the battery to finished running.

Controller Pixhawk  - firmware V3.2.1 .

Thanks, best regards


Artem, I got my first pre-arming error on the new Pixhawk clone yesterday. One I haven't seen before - "Bad Velocity". You seen or heard of this one? Not many hits for it when I search. I re-powered  the copter and it didn't return, then flew fine. Then when I got home I powered it back up to check pids and got the same prearm message with it inside the house. 

that's I thik one of the new ekf errors, are you running 3.3 RCx y any chance? If yes, better to place to ask this question will be the ac3.3 beta thread.. 

p.s. are you using an m8n GPS? 

Running 3.2.1

Yes I'm using a m8n.

by design m8n are much more sensitive than 6m/6h thus they are much more susceptible to noise from the onboard electronics. combined with a lack of proper saw and lna filtering on the cheaper models produces some really bad results even though they show 17+sats and hdop/pdop lower than 1.3. I usually find 3DR leah6h the best gps/compass for multies, even with 10-11 sats and hdop 1.8-2.0 my copters tend to perform better than with most m8n GPSs I've tried. 

Just found this thread, thanks so much for all the data everyone, I have been pulling my hair out trying to figure out this sporadic issue across my fleet of vehicles. I am using HKPilot32 controllers and have had this happen on several vehicles. Given I use these for work, saving a few bucks is not worth the hassle.

I guess my question is, is there a list of known "good" controllers. So far these seem OK?




Maybe the banggood controller?


Any others I should be looking at to replace my currently questionable HKPilot32's? Any chance HK will warranty/replace my controllers? Have they changed or improved them?


Just short the battery connector before powering on as a work-around, and this issue will go away.

I can confirm that my Bnggood controller (same as the one in your link exactly) does not have this issue, whereas an older model banggood controller does have the issue (this one: http://www.banggood.com/PIXHAWK-PX4-Flight-Controller-with-UBLOX-M8...)

Cheers, Paul

My hexcopter has recently had a couple of crashes recently and the only thing that I can put it down to is the control board. I am using a Pixhawk purchased from Hobbyking in January 2015. The first crash I was only about half a meter off the ground suddenly flipping, the next time I was about 5 meters high flying fine for about a moment, I then switched it to althold and it was fine for about 30 seconds then it suddenly decided to start flipping and crash into the ground. The second crash fortunately only broke the cheap legs I had on it so I flew it again with one bent prop and it flew fine.

I know that I also need to do some PID tuning so there are already some oscillations in the readings.

Can someone have a look at these logs and see what they think I have also had bad accelerometer health appear regularly but annoyingly on these two flights I didn't have mavlink connected at the time


Nothing wrong with your IMUs that I can see.

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