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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did you have to redo calibration of compass, acceleromter or compassmot ?

No calibrations, compassmot or retuning needed. Just installed 3.1 

In Mission Planner is it possible to setup Channel 6 Trim for PID Pitch and Roll individually. I can only see settings for PID tuning pitch and Roll together


David Ardis

You can always save your configs and restore it as needed, don´t worry. Save it and restore, if you need it will be there.

thanks randy

Third Aircraft Up and Running with 3.1 & default settings, this time an OCTO-QUAD. Everything flies great out of the box. Theoretically, if you're flying good up & out of the box, Does Auto Tune do anything for me that makes things Better? are there unrealized optimizations from the Defaults? (I am asking from the "If it aint Broke, dont fix it Camp" Camp)


     I'm afraid it's not possible, sorry!  It's not difficult to add so we could do it for AC3.2 if you could raise an issue in the issues list.


     Thanks very much for that!  It's very rewarding to hear that it's working!


    There's actually no way to disable it at this point.  If you're compiling the code yourself you can add some lines into the APM_Config.h file like this:

#define CRASH_CHECK_ITERATIONS_MAX        20      // 2 second (ie. 10 iterations at 10hz) inverted indicates a crash
#define CRASH_CHECK_ANGLE_DEVIATION_CD    2000    // 20 degrees beyond angle max is signal we are inverted
#define CRASH_CHECK_ALT_CHANGE_LIMIT_CM   50      // baro altitude must not change by more than 50cm

So you could possibly disable it by setting the CRASH_CHECK_ANGLE_DEVIATION_CD to be 18000 (or slightly higher) which will never happen because the copter can't be more than 180deg beyond the max lean angle.

I'm afraid it'll need to wait until the release..but we will try and make that soon-ish.

Thanks Randy hope I have added to the issues list correctly

David Ardis

In my mind no I wouldnt do it. Or at least save the settings so you can go back. My Hex flys perfect right now I upgraded and didn't think twice about Not running the Auto Tune. If its working good don't mess with it thats my motto.

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