ArduCopter-3.1 released!

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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              • I'll try it thanks Willy.

            • I don't have experience with Loiter and it's associated gains, sorry.

              Trim Throttle will be changed by the controller during the code, that's why it has changed. Leave it at 590 ;-).

              You can set thr_mid to 590 as well to ensure a smooth transition between stabilize and AltHold, i.e. your hovering position in stabilize will be approx centered stick position and you will not have to change the stick position when you switch to AltHold

              • Thanks for the help Menno, much appreciated :)

  • Well this is certainly not good news for DRONE fliers, Drones Are Now Banned in Every National Park In America

  • Hi all,

    I have an unexpected problem with my new quadrocopter with the pixhawk and AC 3.1.5.

    If I switch to the ALThold mode during the flight the copter became a rocket. It climbes on the full trottle until I switch it back to stabilaze mode. I cant find the problem in logs or settings. Could anyone help?? The same setup with an APM worked great before.

    In the logs you could see that the DAlt after switch to ALThold mode seems OK, but motor out is 100% and baro altitude rise correctly:


    What could couse the problem? 



    Attached logs:
    • Developer


           This is very likely to be a vibration problem.  The rocketing into the air is the classic symptom.  There's a wiki page here which shows how to check using the dataflash logs.

      • Hi Randy,

        Thank you for your answer. The vibratitons were the first thing I checked and it seems to be OK:

        3702656727?profile=originalDo you have another idea? Me not.

        Regards Petr

        • Developer


               Looks like the PILOT_VELZ_MAX is set to 32000!  Normally around 250 is good.

          • Randy ,

            Thank you for the solution. I have checked x-times all the parameters about altitude, power, PIDs.. but didn´t thought that this parametr it could be. 

            It was definitely the PILOT_VELZ_MAX. Now pixhawk flies great. I need to precise the tuning a bit but I feel it will be a great multicopter again.

            Thanks very much :D

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