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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     The Arducopter, ArduPlane, ArduRover code is the same for the APM or Pixhawk for the most part but the way the code is compiled is quite different because you won't be able to use the Arduino IDE anymore.  Details on building with make are here.

Hey Ray,

I'm not a computer guy at all, and I managed to figure out how to compile and upload to the Pixhawk.  It's not too bad with the good instructions Randy linked to.  It's not quite as friendly as the Arduino IDE, but it's not bad.

Other than the actual compile/upload, everything else is pretty much the same.


Recently i changed from 10x4.5 plastic propellers to 10x3.8 Carbon fibre propellers. After the change my quad always seem to oscillation in stabilise mode even after redoing the Autotune. I am also using the provided Vibration dampers with pixhawk. I have run compassmot and got 8% interference only. I have checked the alignment of motors as well as the propeller adapters. Everything is the same as before when using the plastic propellers which were quite stable. My quad specs are as follows,

4 Turnigy SK3 Aerodrive 1130kv motors

Talon V2 carbon fibre quadcopter frame

Gemfan 10x3.8 Carbon fibre propellers

Pixhawk+ 3DR External compass & GPS+3DR Telemetry+Power Module

I have attached a log. Please help me to diagnose what the issue is.



Did anybody test AC 3.1 on an APM 1.0 board ? (a b 2560). With AC 3.1, my sonar doesn't show any value in the test section, while still working well with previous firmware versions... Am I the only one in that case ?


I don't have APM 1.0 but I heard some people used 3.1 on APM 1.0 with a success.

I am certain it won't function as good as it would on APM 2.x but I think it should work.

I'm using 3.1 on my APM1 and the sonar is working fine.  I found that sonar_gain at 0.6 works best for me...

Is the sonar used for any altitude hold functions in 3.1? I used the sonar in the earlier versions pre 2.9 but my understanding was that it was no longer used for altitude hold below 15 feet and was now used solely for terrain following/collision avoidance.

On my quad in order to get prop spin at arm I had to set that parameter to 130. On the second issue, what kind of GPS are you running? Mediatek takes longer to lock than uBlox. At least that was my experience. Also, my FPV camera causes GPS interference and when the camera is near the GPS I can't get more than 7 or 8 sats. If I disconnect the camera then I lock much much faster, like less than 30 secs starting up at a new location or less than 5 seconds if starting up at the same location. I also lock as many as 12 to 14 sats without the camera hooked up. I moved the GPS module farther away from the camera (about 10 in farther away) and all is fine. It used to be up front near the cam and now is on the back out on one of the arms.


I am curious as to what FPV TX you are running. i have had the same problem with my FPV, its left over Devention TX5803 with a DV04 camera. i am thinking of replacing it as i thought Devention was a cheap TX thus the interference

I have a pixhawk coming in and was wandering were do we have a 5v input for RSSI measurements on the pixhawk and how to connect it?

Is it supported with the 3.1 rc1 firmware?

Sorry if off topic.  I am picking up an Tarot Ironman 1000.  I currrently have a 960 and 650 Tarot and PID tuning was fine.  I just got the PID's close and then ran an Autotune.  Does anyone have some general PID's for the Ironman, It is my first Octo and not sure if I can Autotune on the 3.1 defaults.  My 960 and S800 have higher then default PID's and higher Stab P.  I have read info that suggests that on the Octo I should lower the PIDs to start.  Any help would be appreciated!

Many thanks  JEFF

OK just be sure we are on the same page, it was my camera causing the interference, not the video TX. The ImmersionRC TX is the 600mW and the GPS is now closer to it than the camera. All is normal as long as I keep the GPS module away from the camera itself which is a PZ0042. A friend clued me in as to the problem being the camera and according to him most, not all, but most emit RF that interferes with GPS. I can't explain it although he is a radio tech and knows far more than I do. I just took his word and moved the GPS and it made a world of difference. Hope that helps.

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