After months of testing AC3.1 is finally available in the Mission Planner and GitHub.

Warning #1: If the vehicle is left landed (but armed) while in AltHold or Loiter mode for more than a few seconds, the vehicle may suddenly jump into the air the moment the pilot raises the throttle above zero.  The reason is the baro altitude may fall while the vehicle is sitting on the ground.  In AC3.2 this bug is fixed because we reset the target before take-off.

Warning #2: Motors will spin (slowly) by default as soon as the copter is armed!  You can switch this feature off by setting the MOT_SPIN_ARMED parameter to zero.

Warning #3: if you see "Bad Gyro" on the HUD then you may have a blown 3.3V regulator.  See this thread for details.

Warning #4: if you use a sonar set the SONAR_GAIN parameter to 0.8 or lower

Warning #5: Trad Heli users should now connect their main rotor ESC to APM's RC8 output

Warning #6: Trad Heli BUG causes loss of collective control in ACRO mode if swash type set to flybarred (i.e. not flybarless).  Will be fixed in AC3.2.


The major improvements over AC3.0.1 are (full list here):

1. Pixhawk support (Tridge & PX4 development team)

2. Autotune of Roll and Pitch gains (Leonard/Randy)

3. Drift mode (Jason)

4. Improved Acro (Rob/Leonard) and new Sport mode (Leonard)

5. Arming, Take-off, Land in Loiter or AltHold

6. TradHeli improvements (Rob) including:

a) support for direct drive tail rotors

b) smoother ramp-up of main rotor

c) reduced collective for better control in stabilize mode (STAB_COL_MIN, STAB_COL_MAX params)

7. Support for SingleCopter (Bill King)

8. Performance improvements resolve AltHold troubles for Hexa & Octacopters

9. Safety Improvements:

a) GPS Glitch detection (Randy)

b) Motors spin when armed (Jonathan Challinger)

c) crash detector shuts off motors if copter flipped for 2secs

d) batt failsafe option to RTL instead of LAND, gps failsafe option to trigger AltHold instead of Land

e) more pre-arm checks of inertial nav speed,

10. Bug fixes:

a) optical flow working again (although performance is still not great because not integrated with inertial navigation)

b) ROI working (use DO_SET_ROI command)


How to upgrade:
Click on the MissionPlanner's Initial Setup >> Install Firmware screen.  The version numbers should appear as "ArduCopter-3.1", then click the appropriate frame icon and it should upgrade as per usual.

Special thanks to Marco and the many beta testers on the AC3.0.1 thread who put their copters at risk during the testing of this new version and uncovered many problems so that you don't have to!  Here are some of their videos: loiter in wind, patio sonar, autotune, autotune2, roi, beach, acro, vrbrain, tricopter, train spotting, radio failsafe, the tree, double loiter


If you haven't seen it recently, please check out the ArduCopter wiki.


Feel free to post comments below and we're going to use the new APM Forum for support issues so please post your support requests there.

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Duy and all, in future please ask questions in the new forums this is to avoid the super long threads we get here.

Ok, thanks.


     Ah.  The motors spinning when armed is a feature of the release.  See Warning #1 in red in the main part of the discussion.  You can set it back to the old way if you want by setting the MOT_SPIN_ARMED param to zero.

Flashed 3.1 (from 3.0.1) to my f800 with APM 2.6

3.1 Worked perfectly fine without any changes to tuning or compass settings.

Today I had to test AutoTune. (I was a little nervous to try that......but)

It also worked perfectly fine and now my RcTimer f800 Flies better than ever!!! :-) I´m So Happy!!

Thanks for all your great work guys!

And a a Happy New ArduCopter Year!!

  1. Thanks for the info. It does work very well for higher speed missions.
  2. I don’t find the zip file that has the source code. Do you have a link or give me a hint on how use the Mission Planner to get it?




Thank you a bunch. It works flawlessly.

Happy New Year to everyone.  I just got done testing the new 3.1 and its working great along with the my sonar. I left it at 0.8 but noticed before changing over it was at 0.2 and it was not reliable (3.0.1) unless you felt like dropping 20 feet to the ground. Anyhow I have caught the problem before because of my ninja reflexes and saved the machine from any bumps and figured well if it was going to do it again I would be ready but its spot on at 0.8 and I walked under it and it gained alt as it should. Also tested Stab/Loiter/Auto/RTL all worked very well. I ran 2 short auto missions with 4 way points no issues. I did set the gps glitch to alt hold instead of land because who knows what would be under the machine so I figured it would be safer to do this. 

Great work and I will be testing drift and ROI soon enough in a couple photo shoots.


      Here is the source code which is hosted on GitHub.

So we've found a little bug in AC3.1 just now.  The symptom is that you arm and take-off in Loiter and it acts like AltHold.  So it holds altitude but you find that you have full control of the roll and pitch angles.

To reproduce the problem you can do this:

     1. turn on the TX with the flight mode switch already in Loiter mode position

     2. power the APM/PX4/Pixhawk

     3. arm and take-off in Loiter

If somewhere between steps #1 ~ #3 you move the flight mode switch the problem doesn't appear.

We've fixed it already in master and I expect we will push out an AC3.1.1 release within the next 2 weeks.

Special thanks to Ron Hogwarts for finding and reporting this bug in the forums.

Glad it is found and fixed. Is it necessary to wait for a few weeks for the 3.1.1 release Randy?

I assume it can be fixed by compiling the code already but I never tried it; don't feel comfortable. 

I guess you would prefer waiting to see if other bugs come out meanwhile...


how to desactivate the crash detector  or change its parameters?

Crash protection saved my bacon this weekend. I was taking off FPV and just came up quick on the throttle after arming. One of my landing legs was caught on a grass runner and caused the quad to flip over. Crash detection shut it down and saved me from ESC damage or worse. Picked it up, turned it over and set it up right; second time was a charm. I probably would have blamed it on a glitch but the person spotting for me saw the leg get hung on the grass runner so I get the blame for not noticing the landing leg being snagged.

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