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.

Views: 151384

Reply to This

Replies to This Discussion


     The AC3.1.1-rc2 changes are all for the Pixhawk (these changes will be available for APM2 when AC3.2 is released):
    a) Faster arming
    b) AHRS_TRIM fix - reduces movement in loiter when yawing
    c) AUX Out 5 & 6 turned into general purpose I/O pins
    d) Three more relays added (relays are pins that can be set to 0V or 5V)
    e) do-set-servo fix to allow servos to be controlled from ground station
    f) Motorsync CLI test
    g) PX4 parameters moved from SD card to eeprom
    h) additional pre-arm checks for baro & inertial nav altitude and lean angle

I believe there may be an issue with the update not quite appearing for the Pixhawk yet though even though it says AC3.1.1-rc2 on the Install Firmware issue.  This is because of some changes in the auto build system that allows us to separate the APM2 and Pixhawk releases but it's not quite working yet.

Does this means every time we erase eeprom setings are lost and we need to save them before?

Nope.  This is a minor update and there should be no need to re-do the setup.

Hi Randy,

Thanks for the update on rc2 - i just got my pixhawk; is the recommendation with the pixhawk to run this RC2 instead? or stick to 3.1? Just want to make sure I do not have any odd behavior on a 'production' aircraft.

Thank you -


Hello all

I feel like this is a dumb question but i'm not shy so i will ask away. I recently Changed my Octo Quad X frame to a Standard Quad X Frame (XAircraft x650) and was wondering, Would i have to reload the 3.1 the firmware after this change? i didnt think i would because all the X Frames are grouped together? please advise?


     AC3.1 has been flown on more copters so that's probably the more guaranteed choice but there are sometimes issues with the SD card so if you hear one of the bad sounds you might need to move up to -rc2.


     You'll need to reload the firmware.  It's true that in the Config/Setup page's Frame setup screen in the mission planner all the Xs are grouped together but you'll notice when you load the firmware that they're separate.

i kinda thought i might have to just hoping i didnt. but that would explain alot about what isnt happening with the new/old quad. as always thanks randy your help is always invaluable!!

thank you -  I have not heard any bad sounds yet so I will stick to 3.1. I upgraded to 3.1.1-rc2, can I just downgrade back to 3.1? or should I erase/reset the pixhawk & reload params? 

Once back on 3.1..Is the problem with the SD card something that can happen in the air? or will it always happen first at boot? would hate to lose all my params mid flight!

I apologize for all the questions and I appreciate the help

I just reloaded my Firmware for Quad instead of Octo-Quad and i still have Flight Modes? did i do that correctly? when did we start saving Old Data?

The copter's config including the flight modes is stored in eeprom.  The software goes into flash.  Keeping the two separate means you don't need to re-do the config whenever you upload the firmware.  It's like uploading a new version of IE or firefox on your home computer, you don't lose your bookmarks.


      Downgrading to AC3.1 should be fine.  We've never seen a crash caused by an SD card failure, it's always turned up after rebooting and while the vehicle is on the ground.  It will basically fail to start.

Reply to Discussion


Season Two of the Trust Time Trial (T3) Contest 
A list of all T3 contests is here. The current round, the Vertical Horizontal one, is here

© 2020   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service