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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    • Hi Randy, 

          I have a little question. If, I will upload AC-3.1.2-rc2. I need erase and reset parameter before upload to Pixhawk or not? Or, I can upload it without re-setup? 

  • Admin


    I assume that you have connected the GPS to the APM1 board and not the same connector that is on the Oilpan? I believe that the firmware is auto detecting for the GPS that is connected to the APM.


    TCIII ArduRover2 Developer

    • You are right Thomas. It was working when i built it but I think my grandson mistakenly connected it to the wrong port. Ive now plugged it in to the socket on the lower board and its now working. Thnx

  • hello evry1,,

    i've been away for couple of month.. couldn't fly outside been freezing,snowing and windy thought i'll just spin up the TBS quad in the basement..put a lead golf cart battery to hold it down, just in case..which i do all the i plug in my 4s.. apm2.5 with 2.9b fw,did at it should ready to gps lock cuz im indoors..which is always does indoors..

    as soon as i armed it,, it goes full throttle..yikes..turn off radio then on..nothing happens ..still full on throttle..unplug battery, all is off..WTF... replug the 4s and everything was fine..any ideas what could have caused that?.. woke up in

    anyways thought i check in mission planner... but the MP needs updating.. after it ask to to the calibration.compass, etc..checked the CLI.. it upgraded to the FW 3.1.1.. everything seem to be fine.. have to try outside..

    reading bout magnometer..cutting the a trace in apm2.5.. and putting an external..i;ve had a toilet bowl effect randomly on loiter..wlould this fix it..

    • Developer


           2.9 is pretty old so hard to say what happened especially without logs.  Probably some kind of failsafe is my guess.

           Yes, an external compass will probably fix the toilet bowl effect.  Alternatively moving the APM higher up and away from the power wires and running compassmot may fix it.

    • Hi dong, can you post your logs so those expert around can examine.

  • Quick question.  Just to be sure.  If I'm in Auto or RTL and the throttle stick is minimum, the motors are not going to disarm on me unless a "land" is detected right? 

    I want to set the failsafe to min throttle so if my tx fails the craft goes into RTL and lands and disarms.  Will that work?

    • Developer


           Yes, that's right.  It needs to have sensed a landing and the throttle has to be at zero.  The landing detector is quite cautious, i've never heard of a copter disarming prematurely during a land.

      • If the throttle is not at minimum, will it not shut off the motors after landing Randy?

  • This's Hexacopter from my customer. He want install with Pixhawk. after setup and tune is very stable.


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