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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Thanks for the great work to all the team on this release!. For the RTL acceleration issue under discussion, whats the best PID setting to temporarily counter this until a fix is done?

Hi John,

The ArduCopter Development Team is requesting that AC3.1 users post their questions, issues, and feedback on the website: AC3.1 Forum

Please note that if you are new to the website, it takes two Admin approved posts before you can post without approval. The Admins will try and stay on top of the approval process so there will be minimal delay before your first two posts are viewable.



Thank you, Randy


     I would say that you should keep the WPNAV_ACCEL value at 100 (i.e. 1m/s/s) or even higher and you won't notice this fast-stop-followed-by-slower-flight-to-stopping-point issue much.  Also the issue has been there since AC3.0.1 so if you've been happily flying with AC3.0.1 and not noticing it then you shouldn't notice it in AC3.1 either.

Thank you Balloon for all your testing!  One of your videos, the "double loiter" is linked above.

Finally! Congratulations to DIYdrones Developer around the world especially to Randy and Leonard.

My friend Manfred D. and I have been waiting for this release for our 4 traditional ALIGN TREX Helis, 2x 450 E DFC, 1x 600E and 1x 700E DFC.

All 4 flying pretty good on 3.01 so far.

Thanks a lot for all the developers and Merry Christmas to all of you and everybody else.


Yeah, I saw it. Thank you agian.

Great job Team!

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

Many thanks for that great work !

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?

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