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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That is not MSL altitude reporting.  I was at 100 feet AGL. 

Thanks Willy.

I've just found the problem. My save parameter won't work in AC3.1.3 (this parameter flies well in AC3.1.3-RC1). Is that normal? I don't think so.

Resolution: Reinstall the firmware!

I just hope our developers are working on this now. It's just prostrating because since AC3.1.2 there's a lot of fw problems and bugs encountered, one biggest headache this time is the Mission Planner .99. 

Hi, if I update 3.1.2 to 3.1.3 via mission planner. Do I have to recalibrate all sensors?


    No, all parameters are carried over.  The update from 3.1.2 to 3.1.3 is a very small change.

Jay, i also loaded 3.1.3-rc1 before and tested it. anyway, i simply loaded 3.1.3 without erasing or resetting the parameters from CLI. i didn't do any calibration afterwards but my copter flies very well. Maybe, you can reload back the 3.1.3-rc1 and load your original params, then, simply install 3.1.3 like i did. regards.

HI willy, I think no need to redo

Thanks, just update 3.1.2 to 3.1.3 all OK. but I can't find "Position Mode" in Initial setup--> flight modes.

I use MP version 1.2.99 build 1.1.5197.12871

I'm still running 3.1.1 on my Hex, just loaded 1.2.99, went to the full parameter file and loaded the latest saved parameter file from this morning where I change the PID's, everything is working fine, stabilised, land, RTL, loiter and Tx failsafe.

I have not gone past 3.1.1 because I don't want the ability to take off in alt hold or loiter as I have no use for it. I have said it before my Hex does everything it is supposed to and it flies like it is on rails. I have just changed my dual rates to 30% from 15% and it now has given me a lot finer control for precise close in flying to objects.

I have said it before and I'll say it again, Randy and the Dev team have done a fantastic job with APM, for those of you that can't fly without the aid of loiter or alt hold I hope your flying in an area where there are no cars, buildings or the general public, may the force be with you.

Noo, don't change all top props spin CW its better when they spin cw ccw cw ccw...but for efficiency and better handling in wind will be better if top and bottom props spin in same direction, cant find the link now can cuts loses to half......thank you

I think GPS Glitch can save you from some really bad situations, especialy with auto missions....this way if your gps is gone your multi will fly away in only God known direction GKD....

What causes different offsets? I am doing the offset calculation but keep getting different results, I have got my compassmot down to 2% so I am wondering if I should try the learn mode during flight? Any advice

Offsets come from magnets, compassmot comes from current draw through nearby wires. Soon we will also have soft-iron adjustment, which will correct for magnetic field distortions from nearby chunks of non-magnetic iron.

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