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'll try tomorow.
Today we are so sad in France

We are Charlie

Hi Guys,

I have struggled a lot with the same issue using V3.2

S900 using PIXHAWK, Castle Creation CC BEC PRO, etc.

I have reinstalled V3.1.5, and it seems to work now.

Still need to do the maiden flight, but so far so good.

Is there anything I can do for you to help you to understand?



I've carried out some tests and the very limited results would suggest this phenomona is temperature related.

Leaving my quad in the boot of the car overnight resulted in a pre-arm fail on the last two mornings.  The temp was 2 degrees  and 5 degrees (celsius) (as shown by my car temp gauge).  I tried to arm 3 times in a row each morning and each time the pre-arm check failed.

I brought the quad into the house and left it next to a radiator for an hour, retested and the pre-arm checks passed (first time on each morning after being warmed up).

I will continue testing until Friday and post results.



Yeah maybe temperature related as well...

Was cold the day I had in mind to do the first flight, like -15oC (5oF)

Had issue with the ACC, tried to calibrate the ACC outside without any relevant result.

But S900 has been on my table for a week at same temperature and it has refused to arm because ACC / Horizon was not straight.  So... not too sure it is temperature related...



try disconnecting your backup BEC and see how it goes. In my case almost 2 weeks with no acc issue even when I was in the mountains about -10 Celsius...

p.s. my acc problems started when I connected a BEC for landing gear, after I moved BEC to Rx and disconnected power wire from the sbus plug I have no issues... almost 2 weeks now. 

I only have the CC BEC PRO nothing else...  The power module is not strong enough (45 amps).

And I have other modules as well

Spektrum TM1000

Spektrum Current module

Spektrum GPS module

AR9020 + 2 sats

915MHz Telemetry



what is the voltage of your castle BEC? 

default I think it was 5.1V when I measured it...

We would need to check and compare it with the power module.

INRUSH, Startup, overshoot, undershoot, etc.



Just to let everybody  know how this issue effects my trad.Heli with the 3DR PIXHAWK Autopilot. Installed: APM-FW 3.2

For the motor I use 12 S ( 2X6S LIPO)

For the HV Servos = one 2S Lipo

For the Pixhawk , the 3DR Power Module = one 3S Lipo

The 12S get's monitored by my TX Telemetry.

I have the pre-arm error 'Accel not healthy' only and each time when I connect the 3S LIPO first (3DR PM for the PIXHAWK) before the 12S  (50.4 V).

If I connect the 12S first with a bit of a spark everything is fine. Even if I connect the 2S Lipo for the Servos after the PIXHAWK  the pre-arm error does not appears.


8 years of flight with Multi you say....you must be very experienced pilot.

Yes,8 years about 800h of flight.

Started with X-ufo silverlit with mechanical gyro ;-) (end 2006), that i'd changed for ASCTEC piezo gyro, after UAVP (first gen based on PIC) then Mikrokopter.

In 2009, i joint French company that try to make some uav, as program manager for multi-rotor, they use Paparazzi.

i'd designed for them about 12 different frame from nano quad to big hexa.

I' was the pilot too, for test, demo, services.

I'm the first "télé-pilote" according to the French aeronautical administration (DGAC)

And now I've my own business for instruction, advice, and i develop my own omni-role multi rotor according to the French regulation, based on one of the best UAV system that I've to flown: Ardupilot ;-) that i used for about 2 years and that make me stop (among other) my collaboration with the company ;-)

Voila! you now everything, but we are now fare aways from our issue ;-)

i'm going to fly this afternoon, unplugged the 5V Ubec and see... there's about 30 to 60km/h of wind, i love;-)

I Get Bad Lidar Health ... but it works.

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