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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I've returned my pixhawk to the person I bought it from - turns out it was a clone.  Even had the 3dr logo on it and everything!  Turns out if the price is too good to be true, it probably is.  Fighting to get a refund now, good thing I used paypal.

Not sure if it was 100% faulty board, or maybe in some clones since IMU2 was never really used before 3.2 is just find preexisting issues doe to stricter hardware checks.


Just to say that I have this issue too. Twice, after normal flights and landing, I can't rearm : message like "bad_health_accel".

First I think it was an hardware pb : calibration failed on the field , but after recalibrating OK at home : flight 20 mn OK the week after.

One more week after : flight OK of 10 mn (just start to drift a little in loiter mode), landing OK ant then accel check pre-arm message.

I will try to set the logs for next time the problem occurs.


Yup - been having this with a FixHawk ever since late beta. 

Most common was compass inconsistent but a variety of other messages all of which do not go away with recalibration etc. Sometimes swapping battery means you can fly, other times not. 

Something changed in the code - must have - to make this occur. Even Randy said he gets the errors sometimes. 

Is it happening to anyone with a 3DR Pixhawk?

Same issue here, prearm check fails due to bad accel health since I switched to APM 3.2. Sometimes it's fine, and sometimes it takes 20 restart attempts. When it works, it flies fine until i disconnect the battery. Mine is a RTFHawk from witespy. I doubt it's a HW thing, since there was no issue on the older APM versions.

I have been running 3.2 for months now and never seen your issue.  Reviewed several logs and not seen any issues.  Have had problems with GPS drift though due to buildings and take off issues due to early bugs that have been corrected.


Log from my pre-arm fail today with bad accel health.  Quad had been in car at 2 celsius for the night.  Shows same difference between IMU and IMU2 AccX readings.  Also Y and Z axes affected.

Hobbyking clone board.

Hope this helps.


Is yours an official 3DR pixhawk?  Also, are you in a warm climate?

Thanks everyone for speaking up - I'm not sure if the Devs are looking into this or not, but I'm going to send them a message.  

It was 25 degrees Fahrenheit or -3 Celsius. I left the copter outside for about 10minutes before I armed and flying.


Hi Josh, we're looking at the problem whether it's 3DR boards or others.  But, it's not easy to figure out what the problem is.  It's entirely possible, and likely, to be a hardware problem that has nothing to do with the firmware.  It's also possible that this had been happening for a long time, and it's only with 3.2 that the problem is visible because we were not checking for it before.

I wouldn't expect there is going to be any fix that will "roll back a change". It's pretty common when these sorts of things happen that people think it's something we did.  GPS problems are classic.  But it's normally nothing to do with firmware changes.

Tried it again today at 17 degrees Fahrenheit or -8 Celsius and left it outside for 30 minutes.  No issues.  This is a real 3DR Pixhawk.  I would say that the Barometer is not very accurate for showing temperature.  It showed that the temperature was 8 degrees higher Celsius than it was out and that while flying high in the air the temperature went up.  Shouldn't the temperature go down the higher you fly?


Not sure about the baro - but this falls in line with my theory that this is affecting clones/third party boards only.

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