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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What Parameter tells you that the aircraft hit a failsafe in the Logs? Thanks

Hello Marco, I've never had any problem with that also. I first encountered it when running rc7 on a tri-copter, which I didn't have previously. I checked a quad setup and it performed ok, so it might be related to a tri-copter setup. The problem on my tri can be repeated, it's only in loiter. It stay's in place perfectly, height and position, but hitting just yaw, left or right, triggers something in the logic. It drops like 20 - 30 meters and recovers if yaw is released quick enough.

I'll check the code and try also with the final 3.1 release. If still present I'll put an entry in the issue list. For now it's sufficient to be placed here. Maybe some other tricopter user can check if they have a different experience.



I am upgrading to the 3.1 from 2.9-Is there a list of parameters that need to be adjusted as you suggested in 3.0 version?


    You'll want to do these things:

           1. reduce the Loiter gains. Check out the small screenshot about half way down on this wiki page.  It has the parameters on the APM Copter PIDs screen that should be adjusted.

           2. make sure that the interference on the compass from the power wires under the APM are low.  So either run compassmot or use a separate GPS+compass module.

           3. if you use a sonar you should check the SONAR_GAIN parameter is set to 0.8.

           4. you may want to check that your 3.3V regulator is ok before you upgrade.


     They appear in the "Err" messages.  So for a throttle failsafe (also called radio failsafe) it will appear as:

          ERR, 5, 1

     When it clears a line like this will appear

          ERR, 5, 0

     There's a list of all error messages on this wiki page.

     Separately there's a request that the mission planner display these automatically when you graph anything from the logs.  I think Michael is planning to release that with the next big mission planner release.

thanks Randy, that would be helpful if it you could graph that. i think i hit a battery fail safe, i could see when graphing, the modes appear as labels in the graph, my final label was an RTL but it doesnt tell you what caused that RTL.


     Normally what I do is filter the first column to only look for ERR messages.  You can also filter for MODE.  Sadly it doesn't allow you to filter for more than one message type.


The wireless communication on xBee has been done by this way.

The speed is 56K bps.

Basically, I cut the 6 position wire harness along with Pixhawk and made connectors on the other end. This interface board is made for 5V logic level converter, but works just fine.

I have not yet connected the i2c socket on it yet .. as I have not needed to .. my JR radio displays all the info to me in big letters on a large screen .. and I have my radio set up for different alarms (battery volts, amps,  altitude, capacity, vario etc) Since the unit can be used with a laptop to collect all this live data via the onboard connector i dont see why it could not be used by the Apm 

Randy, do you know anything about the I2C port? is that considered a serial port?

Hi Randy, happy 2014!!!

I just updated my PX4 to AC3.1 and after that I have no data from my spektrum satellite receiver  when I try to do the radio calibration (the biding led on receiver is orange that means found TX)

Could be any incompatibility with the new firmware? Do you have noticed the PX4 satellite receiver port was tested on AC3.1 for anyone?

See you,


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