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 cant find what the change was between 3.1.3 and 3.1.3-rc1

3.1.3-rc1 is a beta firmware. 3.1.3 is an official release in MP. i think they are the same.

Yeah that's correct. That's why the twitch on rtl still there. Be careful not to use it on windy condition.

As an experiment I replaced an APM2.5 with an old APM1.4 on my tricopter and I'm happy to say it works really well using the exact same parameters (apart from the few small APM1 specific differences).

Loiter holds position very well but Alt_Hold is all over the place, jumping up and down or dropping suddenly, now I know the baro is older and not quite as good as that in a 2.5 but is there any way (or parameter change) to get Alt_Hold to not bounce around on an APM1?

If you are using a code 2.9.1b or later, the alt-hold shouldn't be fluctuating that much since starting 2.9.1b they implemented the inertial navigation. This means altitude controller isn't looking at the baro output only, it also uses accel. z value... Might want to check and see if there was a parameter that enables/disables accel. z use for altitude.

I do not remember it now...

No, this is with v3.1.3, using the same parameters as the APM2.5. My vibrations are low, all I changed was the APM and now I can't get Alt_Hold to alt hold so it must be a hardware difference.

I think i found new bug. I am using Mission Planner 1.2.99, brand new Pixhawk, loaded 3.1.3 fw and setup controller with wizzard. During setup i choose X frame type, then i go to Mandatory Hardware > Frame Type and it says + type.

+1 I've notice it as well. 

Graham, I had 3.1.2 working fine with Alt Hold on my APM1 board. Ive now loaded 3.1.3 but haven't tried it with Alt_Hold yet. I also have a sonar fitted to it

+ 2   it happened to me as well .. i had one flight after doing setup and noticed it was not responding correctly to radio inputs .. landed and checked all settings in MP . found it was + instead of my first selection of X .. since then i have uploaded 3.1.3..  and checked control and it was still on my correct selection of X.

same here had a crash since it was on + mode instead of x.. justed updated the MissionPlaner connected once and there it went from x to + !!!


The wizard is a big time killer for that.  If you accidentally click wizard, it will default your frame type to +.  You don't have to click or do anything else.  So just accidentally clicking the wizard will change your frame type.

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