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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  • Finally Got Thru Autotune on my quads (because the Winds in Florida Finally were acceptable for flight) seems to have gone quite successfully but during the Autotune process I noticed that ALT HOLD would Descend a Bit.

    isnt AutoTune Based on Alt Hold? Also Loiter did Some thing Similar, i'll have video Later of it but i am thinking i just need to increase the ALT HOLD PID from 1.00 to maybe something like 1.10 maybe 1.15/. also thinkinhg an increase on the RATE LOITER/LOITER PID up from 1.000 to about 1.100 or 1.150. Would i be correct in this assumption?

    My THR_MID is 500 but when i am in stabilize and click to ALT HOLD i seem to drift Downward, in LOITER i can hear the motors surging slightly, like it needs to rev a little to maintain flight?

    any thoughts are greatly appreciated

    • Surging motors would be caused by the THR_ACCEL_* parameters. A steadily descending copter would be caused by not having the stick centered. Descents during fast flight are caused by air movement over the copter, this is normal and there's no way to solve it.

      • ok thanks for replying, so i am going to increase, in the extended tuning, the Throttle Accel P from 0.75 to 1.00

        decrease the Throttle Accel I from 1.50 to about 1.25 leave the D alone?

        I assure you my sticks are all at 50% throttle.

        i feel like i would want to increase the Loiter Rate P from 1.00 to about 1.10 and leave the I and D alone. maybe raise the Loiter Rate IMAX from 4.0 to 5.0 this would solve the Loiter descent

        My problem i have currently is trying to smooth out the THR_MID so that its Equal to the Stick Position of ALT HOLD & LOITER, currently i can get off the ground and hover at 6 feet at 45% throttle in Stabilize

  • another point to read release notes:  warning#1   what I thought were sync issues with me going up in lipo count was actually APM setting all motors low.....

    2 times it dropped from the sky and I switched motors at the same time updating to 3.1.3  and flew for a week w/o issues.

    now after this post got in the top again, I read the first paragraph and bam,,,,, went off to try my old motors which I meant to sell, so far no issues! guess I will keep them ;) 

    let me know who to thank for actually finding this bug and fixing it! 

  • Have an Error On the New mission Planner 1.30 RC_FEEL_RP Not Found or Failed, didnt get this in 1.2.99. what is it? Also i get a message that says, there are no Min Max Settings or something like that in Mission planner 1.30?? anyone else getting this?

    • I am getting the same error in mission planner
    • Same here...

    • I get the same messages.

  • I can find hybrid flight mode in MP1.30 with arducopter firmware 3.1.3 now。Does it mean the firmware support hybrid mode?
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