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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     Looks like the PILOT_VELZ_MAX is set to 32000!  Normally around 250 is good.

Randy ,

Thank you for the solution. I have checked x-times all the parameters about altitude, power, PIDs.. but didn´t thought that this parametr it could be. 

It was definitely the PILOT_VELZ_MAX. Now pixhawk flies great. I need to precise the tuning a bit but I feel it will be a great multicopter again.

Thanks very much :D

Not sure how to reply to the Feb 20th discussion since it's marked as a permalink (not sure what that is on the forum) on altitude resetting after changing to loiter mode.  I know Jonathan Challinger replied that it seems to be a MinimOSD bug, but I can't find further discussion to track it.  I'm having the same issue with arducopter 3.1.5 and have been searching all over for the resolution for days now.   This seem to be a dead end but also seems to be the last update on the issue.

in FW 3.1.5 Circle Mode, is it still measured in Meters? is the Wiki correct?

Also When slowing down quickly from a forward motion, my quads seem to BUCK like a bronco, where do i need to increase the D parameter to smooth that out? having alot of fun with these quads nowadays, thanks again fro everyones good work!

Tuned the octaquad nicely in loiter for position holding, even in strong winds but still can't make it hold a height. It behaves really nicely in stabilised, I try to maintain a stable altitude then select loiter. As you can see from the log, it then starts to climb. I have to lower the throttle virtually to the minimum to get it to descend, then up again to make it climb. There seems to be a huge dead band on the throttle in loiter.

Using RTL it maintains a rock steady altitude, so I am a bit clueless as to how to stop this loiter altitude issue. I have recalibrated the radio and obviously the alt sensor is OK otherwise it would not maintain a perfect RTL altitude.

Anyone got any clues as to what to do next?

Recently I had this issue on a little smaller scale with an overpowered quad (hover at 25% throttle) you need to adjust you throttle mid in the MP, as the AC by default expect the throttle mid be in the 40%-60% range. I suppose you are trying to fly an "empty octa" with a smallish batt for the tuning purposes, am I correct? If so, add some deadweight on it for the purpose of tuning, than when you are done, you can replace it with a valid payload.

Hi Artem,

No quite the opposite, it is a heavy octaquad and I was out on a surveying job, so double batteries and camera with mount. The throttle seems to be correctly set as when I am more or less mid throttle and switch to stabilize from any other mode (like alt hold etc) it stays put. Same when switching out of RTL to stabilised.

It just seems to be switching to loiter that this occurs and off it goes climbing away, baffling!

Quinten, hows the vibrations on the craft? i know i didnt solve my problems until i really tackled the vibration problem by buying whats mentioned in my video 

That was my thought at first, so when I looked at the log it seemed quite good, in fact must have been as the alt hold was perfect in RTL.

I also Know that Marco had said you can get a dependable THR_MID from the THR_TRIM, it also seem to help me after changing it. that is the estimate by the FLT controller of what it needed to maintain hover, it has worked for me but it DOES change depending on what you load on the Aircraft. hope thats helpful

Thanks for the info, yes I had already adjusted that.

For Firmware 3.1.5, is Circle Flight MODE not working properly? I have a 4 meter circle set for two quads, an X650 and an F450. it KINDA worked on the F450 but was erratic, never fully completing the circle, it would drift randomly then . the X650 backed away from start point, then never got into circle mode but it seemed to drift. i know it worked in 3.1.1, but not so much with FW 3.1.5. any help is appreciated

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