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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  • 3.1 is a great Christmas present. Thank you team for your extraordinary efforts and continuously striving to make this a great success.

    Best regards,


  • Many thanks to the team.

    already fly with RC7, Auto tune work very nice and overall it feels much more mature.

  • Just a quick note about 3.1 for TradHeli:

    First, an important note.  I have not tested Auto Tune on TradHeli, and I very strongly believe that it will not work for Tradheli.  Tradhelis gain most of their control from the Feedforward term, not P-term.  Autotune is not aware of Feedforward and only works with P and D.  Further, the D term that autotune will attempt to use could possibly cause an in-flight failure.  I do not recommend anybody attempt Auto Tune on a TradHeli.

    Most of the changes I had been working on in my 3.0.1 branch for TradHeli have been implemented in 3.1.  However, they were significantly reworked to fit in better with the new direction the code is taking ("onion").  I have done a fair amount of bench testing to make sure these still work as desired.  But due to a number of circumstances, I haven't been able to do a lot of flight testing.  I will try to do some more ASAP and will inform if there are any problems.

    I did discover one issue last night with the way Collective-Yaw compensation is done.  It's a minor issue.  Basically, the compensation switches on and off with the motor finishing it's ramp up and NOT the simply motor on/off as it should be. (ie: torque comes on soon as the motor starts).

    This bug has actually existed for a long time, and so the inclusion of this bug is actually not anything new.  Most of you already have this bug if you're using the older code anyway.  It's just that my fix was missed.  That fix is now in trunk and you'll see it on the next release.  As long as you aren't turning the motor on and off in flight, you'll never notice.

  • superb randy.. I will load the 3.1 fw version. can I use my channel 6 rx for auto tune? I only have 6 channel rx max to run apm, channel 5 for mode..

  • Hi all

    I know this question has probably been asked a million times, when upgrading to APM 3.1 etc. do you loose all your previous setup values, do you have to start from scratch to calibrate everything?

    Maybe this can be mentioned in the 3.1 upgrade spiel.

    By the way, I just got a 3DR quad and with no wind yesterday in Adelaide I did a blueprint autotune - just perfect.

    Went flying today and was very responsive - have not managed to put it on its lid yet.

    Without pushing too hard in testing - altitude 60m, speed 61.2km/hr



  • All we need now is an equivalent flight mode to the Naza GPS mode and the APM would be exceptional :)

  • Thanks Randy.

    So all forum topics will now move to APM and DIY forum will be phased out? I have registered and will post there from now on.

    Also is this an error on the list above "The major improvements over AC3.1 are (full list here):" and it should read AC3.0.1?

  • Many thanks for that great work !

  • So happy to see this release in the wild. It certainly has had some extensive testing done and delivers so many great new features.

  • Developer

    Great job Team!

This reply was deleted.


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