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 have already did that, but no responses too. Thanks any way.

can autotune be done with using only sonar to lock alt hold and without using the GPS to lock height and position?


     Yes.  In fact AutoTune normally works while the vehicle is in AltHold mode so it does not require a GPS.

Thanks Randy. Thats good news so I can try out auto tune indoors. So then say if I use my other rig that doesn't have sonar, then of course GPS is required right? 


     I couldn't find your issue in the APM Forum so I'm going to answer here.

     Although the vibes do look like they're within the official limits I think it is still vibration that's causing the problem.  In general I don't see anything too wrong with the altitude hold, no sudden jumps, but the altitude hold estimate does vary from the baro estimate by more than 1m at times.

As long as you get the power disconnected as soon as possible most electronics should be OK if its dried out properly. Most people who drop their phone in the water don't take the battery out immediately and that's what kills it. Its the stray electricity and the electrolysis eating the circuitry is what damages it

Hello everyone and Helllllllllllppppp me !!!!!,

On both my quad , I have installed version 3.1 and they are very "soft" power , I increased the value trottle_max to 2000 to find a slightly correct reactivity , but it is not viable , it also has a derivative in yaw to the right, if I change the yaw , it loses enormously altitude.If I go back in v3.0.1 , no problem after the initialization and calibration .. Of course whenever a reset and erase . the frame are two TBS , same ESC and the motors.
I continue to test the beta version 3.1 on one . but I can not seem to eliminate the problem of power, which does not occur until version 3.0.1 .
I even tried on Y6 which does not have the same ESC / motors and I have exactly the same problem of power, and reaction to the change on the Yaw .

Is there a particular parametrage for power 3.1 because , I absolutely do not understand what is happening . I tried full version but the problem appears systematically with version 3.1 and supp .

thank you very much in advance for any help you could give me


Thank you very much Randy. In this log you don't see the jumps because I attenuated the THR_ACCEL_P, so in this particular flight the Althold mode was very "calm".

Thank you for the log analysis ;)

John, I may be wrong but my understanding is that it will use the accel z axis and baro sensor for altitude hold if you don't have GPS. If I understand correctly that's how it is normally operating anyway even outdoors. GPS is not very accurate in altitude so it not used for alt control. Again, I may be mistaken so maybe Randy or someone else can elaborate.

Your understanding is correct Butch. GPS is not required for alt-hold mode. As you mentioned, even though it provides 3D fix, the GPS altitude is just an estimation and cannot be used for precise altitude control. Baro sensor and the z accelerometer are the ones that run the alt-hold mode...


     setting the throttle_max to 2000 will cause problems so you should definitely return that to 1000.  Reporting in the forums is probably the best thing but also including a log file will help.  I think when you do that log it would be good to enable the MOTOR log message.

By the way, sorry that I haven't been able to do as much log analysis recently.  The issue is that there's just so much demand for log analysis that if I try to do it all I can't make any progress on the development side and that'll seriously delay the implementation of the vast number of enhancements requests.  I think we've dug up a few people that are willing to pick up some of the support load and at least one other who is looking at some automatic log analysis tools so hopefully that together will help answer some of the demand.

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