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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  • Hello All, this question maybe MOOT by the time Firmware 3.2 is released (because as i understand it, taking off in ALT HOLD & LOITER will be the same as Taking Off in Stabilize) but i will ask anyway.

    I am Currently having a throttle problem in ALT HOLD and LOITER. In Stabilize, My THR_MID is 400, i think the Log Shows that to be true, thats what it was yesterday any way. I am trying to increase my ALT HOLD PID and LOITER PID because in my Mind that may stop the Descending behavior even though my Throttle is at 50% when it happens.

    The Quad has been Auto Tuned.

    what i hear from the motors sounds like a REVVING sound as it tries to maintain altitude. Attached is my Log, Am i on the Right track here?

    Thanks in Advance

    2014-05-05 10-45-21.log

  • Is it possible to change the analog input the sonar is connected to?  0 on my APM 2.5 is no longer working (as tested both with a sonar and a variable voltage power supply connected to that input). The sonar is fine.  If there is a parm that sets the analog input the firmware listens to for the sonar and I could change that I'd have the sonar working again.

    APM 2.5, Arducopter 3.1.2, 3DR 2013 quad.

  • Does the warnings from 3.0 also apply for 3.1.3?

    That is:

    Warning #1: Compass calibration and reducing interference is far more important than with 2.9.1b

    Warning #2: GPS glitches can cause sudden and aggressive position changes while in loiter mode. You may wish to reduce the Loiter PID P to 0.5 (from 1.0) to reduce aggressiveness (see image below of where this gain can be found in mission planner).

    Warning #3: optical flow is not supported but will be back in the next release (AC-3.0.2 or AC-3.1.0).

    Warning #4: loiter turns does not maintain altitude. This bug will be fixed in AC-3.0.2.

    Warning #5: This release has only been lightly tested on Traditional Helicopters.

  • Hi Guys ..

    I have set up channel 7 for simple mode on a separate switch.. so i can fly in any mode .. and switch manually from simple to std at any time I wish, problem is that I see MP does not "announce " the fact the simple mode has been activated like it does with the other flight modes .. Do i need to set something up in MP or is voice function for simple mode not yet avail ..


    • While it is not in the code for the moment, you can set up voice anouncements in your TX, if you use Taranis or Turnigy 9x/xr with OpenTX Firmware

      • Hi Alexsey   Thanks for your reply and additional informational video..

    • Developer


           There's no verbal announcement and in fact, we don't send any info to the mission planner that would let it know that simple mode has been enabled.  In fact, we don't even have a MAVLink message that could be use to send this info.  Simple mode is not really a flight mode, it's more a modification on how the pilot's inputs are used.

           It's a totally reasonable request that we add this of can add it to the issues list if you like.  There's one for ardupilot and mission planner.  It would require changes in both systems.

      • Thanks Randy for your swift and kind reply ..

      • Do I also need to make request about X8 octocopter motors spinning direction(motors on same arm spinning in same direction) together with motor numbering order?

        I did it,hope I didn't mess something there,my first time submitting something....

  • i think this issue of not descending in RTL is also related to a problem i noticed in 3.1.2 and 3.1.3 is that after the 'Takeoff' command in mission planner, the next command is not executed which is typically a 'Waypoint' command. the craft keeps hovering after 'Takeoff' command. may be this would also be resolved in AC3.2

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