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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I've been looking at the log file for a while but unable to determine why my tricopter just fell out of the air. Looking at the video, it sounds like the left motor/ESC failed after a short left roll control from the control stick. Can someone more familiar with the log file have a look to see if this is a hardware problem?



     That is super cool.  How are you activating the sprayer?  You know that there's a sprayer library in ArduCopter?  it's not well documented but it can be enabled if you compile the code yourself.

     We're going to fix the issue with the internal compass not being calibrated in AC3.2.  This affected me personally at Sparkfun because the external compass failed on my final run and I ended up with the vehicle doing toiletbowling.  So I'm highly motivated to fix the issue.

Hi Randy 

Yup cool alright ! lol ..  At the moment I am only using the throttle cut switch on my transmitter , to activate the spray pump, but plan to use something like "do digi control or do servo control" So the Pixhawk will activate the spray when requested in a flight plan. 

P.s I am still using 3.1.5 code not 3.2 .. I don't know why the internal compass is faulty .. So you think its just software based issue?

One of my biggest challenge's with what I what to achieve with my UAV's

Is having Precise altitude control when flying over Orchards and RTK Gps such as Piksi, So the machine stays on target .. Hopefully the team (you guys) will have a solution worked out in the near future ..

cheers Reuben


     This is very likely to be a vibration problem.  The rocketing into the air is the classic symptom.  There's a wiki page here which shows how to check using the dataflash logs.


     The sprayer is available in AC3.1.5, it's just disabled by default.  I'll try and put up a wiki page to describe how to use it.

     The internal compass calibration not working is a mission planner issue which MichaelO will sort out shortly.  There's an issue in arducopter which can mean the wrong offsets can be used though which I will fix.



Good to see you at SF.  Do you know how many ended up in the water by the end?  I had to leave about 1:30PM.

May I ask where the sonar is in AC3.2 for APM?  I've been holding off going to the latest release until I see the sonar will work again.



     It was a big year for crashes.  Nobody went in last year but this year I think Three planes went in over the day (Philip Rowse's, Michael Oborne's and Greg Fletcher's) and Rob's trad heli went in the previous day during a practice run.  I think 1 copters went in the water but I forget which one.  There was one trad heli that had a bit of a scary high speed crash into a fence (incorrect power set-up caused brown-out) and a multicopter that went to one side of the crowd.

RE: alt drop during forward movement. Is there a parameter to tweak so the copter would prioritize inertial data over the baro during horizontal movement? 


first off, I'd like to suggest to cover all big holes in FC case with tape. that will reduce the effect a lot.

then you can increase INAV_TC_Z, but just have a look at that:


tanks for your help, todays flights were AWWESOME!!

Hi Randy,

Thank you for your answer. The vibratitons were the first thing I checked and it seems to be OK:

Do you have another idea? Me not.

Regards Petr

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