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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Please ask and answer questions in the new forums now, we don't want this turning into a huge thread with information dotted all over the place. This is the new spot

But of course, you can switch the RC receiver CH6 input into CH7 of the APM input.

i.e. if you have a PWM output receiver.

And then use Autotune with CH7 enabled on MP.

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.

Many thanks to the team.

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


     Today, I have test release version is still perfect and no problem in loiter and RTL. I will test another mode again on tomorrow. And I waiting Pixhawk for test it same.

Great Work for Release Version for APM 2.5 and 2.6.

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,



I tested today wind speed the version at 35 km / h, with all mods
ROI works fine. Loiter 1A,

Thank you to the team, a very good work.


Well done guys .. what a great achievement ..A big thanks to all from New Zealand .

Congrats! Best tested (and best performing) code ever. Super proud of the whole team!

Thank you,

I just did a torture test of the autotune due to lots of soft snow...

A well overpowered quad with very, very bad PID values (I made them too big on purpose, closer to the "defaults"  - the quad was barely able to fly, but autotune got it right anyway, after 1 minute or so, it was no longer flying like it was about to crash, when completed, it flew well.

One thing it did not touch (as expected) ws YAW pids, BTW,; is there a "rule of thumb" for yaw PIDs ?

The base version of Randy's 3.1 Release page is now in the Wiki as well with links back to this discussion so people can see the comments too.

Drift mode....

Oh god, I've wanted this for sooooooooo long! I'm upgrading to 3.1 just for this feature on it's own. Just got the agony of the waiting now until the weekend when I can try it out.

Just simply awesome work guys.

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