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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    • so now...

      AC3.1.5-rc is for APM & PIXHAWK

      AC3.2-rc1 ---- and upcoming firmware are on PIXHAWK

    • on AC3.1.4, if I hang the drone to a post via a wire, I switches to Loiter mode and I tensions the wire, and I set max angle 25 °, why drone that leans at 30 ° or more?

      I know it really is not very common as a question, but I would like your point of view or that come to mind without thinking too much.
      • I don't believe that what you are trying to do is achievable, if the centre of gravity of your multi rotor is not perfect where you have attached the anchor point it will react as if the multi is way out of balance when the load is applied to the wire. You may even introduce harmonic vibrations.

        What are you trying to achieve?

    • I'll test AC3.1.5-rc1 on weekend with my new cheap "sacrificial" copter. Too much money wasted in the past, especially bcs of motor shut downs til 3.1.2. (my new Pixhawk Quad isn't on earth anymore. crashed two days before 3.1.3 was released...)

      On my main frame, I decided to install reduntant motors (X8) as a failover solution. Til now I'm not sure if APM and Pixhawk have a hardware issue with the PWM-out driver or my cables sucks.

      Randy, do you think there is a possibility to log the real PWM outputs? Maybe somebody has a pass-trough data logger for pwm or you could code a loopback-measuring routine for wich we have to build and use a small adaptor bridge? (for CLI or steady use)

      Thx in advance.

      Btw, 3.1.4 went well on APM:


      kind regards Christian

  • When the battery failsafe is triggered switching the qua to land mode, should it do a continuous steady descent to the ground. When mine triggered today it descended steadily from 30m to 10m then stopped descending. I had to switch modes from land and control it manually to get it to start descending again so I could get it down before the battery failed.
    • Developer


           That's an issue that is fixed in AC3.2.  It happens because it first aims for 10m and then below that it descends at the LAND_SPEED.  The problem comes when it gets really close but never quite reaches 10m.  It will eventually get there but it can take a while.  In AC3.2 we replaced the 10m target with a descent speed target.  So above 10m it descends at the regular speed, below 10m at the LAND_SPEED.  Sorry for the troubles.

      • Hi Randy

        Is there a place where we can find all the changes that have been done, except reading all the commits at github.

        • Developer


              The ReleaseNotes.txt files has most of the improvements.  It's a big list and although I try to make the point understandable there's a lot of changes and getting your head around everything is a challenge.  Still, better than trolling through GitHub I suspect!

          • My point

            this LAND_SPEED issue was implemented Dec2012 on fw 2.9, and I couldn't find more references to it.

            Your excelent explanation above should be there :) or somewhere else TBD.

            but short of sending everybody to github, I believe that a more "consumer" friendly status location would be beneficial.

            Also, and please don't get me wrong, most of the improvements is not acceptable. What, IMHO, is needed is all of the corrections and improvements. That's why I try to follow the commits......

    • What is your RTL final altitude or something like that...

This reply was deleted.


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