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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Yes I did it intentionally to show a friend the full throttle accelaration..

due to too high current the integrated power distribution board got a burned copper trace next to the battery solder joint. But it doesn't matter, that quad is build for experiments. So I don't need to sacrifice my other expensive FPV copter..

Thanks Christian. I just wanted to make sure it is not 3.1.5 bug since I plan on upgrading soon.

BTW, I meant to call your name in my previous post but said "Bill" mistakenly. No way to edit that unfortunately. But you figured it out:)


3.1.5 is the most stable release, so I use it on all of my friends copters. When they come for a repair, I know it wasn't the software.. Since we use at least LEA6H or M8N GPS I can eliminate GPS issues.. (pls don't use NEO6M any more)

Sure I am using ublox Lea-6H. No intention to change it over...

RTH works flawlessly.. like showing it off to newbies..

but sometimes when activated at a fair distance..i'll go up to required height then stops and jus stays there..will not turn and head home.. i have to flick RTH switch off then on..then it will turn and head home..confused..any ideas..

@dindong, Did you figure this out yet? 

  I have flown my quad-copter with apm 2.6 , v3.1.5 for a mission of photographic surveillance many times without problem, but yesterday after completing the misssion , I moved back to home, at the same time I also lowerer the altitude for landing, but suddently it lost contronl and wobbled down from 180 meter height . I even changed mode from loiter to AltHold and Stabilize, no use at all.
 The wind at ground is about 3 to 4 Beaufort Scale.
 The normal fly time of my copter is about 12 minutes, I flew back after  7 minutes.

  Could someone help me what is the problem?

The attached video :


похоже на отстрел лопасти 

I went back to V3.1. My quads don't seem as stable with V3.1.5.  Could something have changed that would affect vibration between V3.1 and V3.1.5? It seems that with V3.1.5 my x and y values diverge from each other more than they do with V3.1. If it's calm tomorrow I'll do similar flights with both versions and post the logs.

Why don't you try the 3.2? it's beta but many test were done, my cuad flies better with it ;)

I'v been thinking about giving 3.2 a try. It's encouraging to hear that your quad flies better with it. What size quad are you flying? I have a Talon 550 and Tarot 650.

Question about position hold on V3.2rc12;

in several quads, when flying fast in POSHOLD and release the sticks, the quad slows down, tilts against the flight direction and stops. (basically this sould be th end of the stop) but it then tilts back in flight direction slightly, flys forward a bit more and comes to a complete stop.

which parameter would you tune in this case? 

as mentioned it happens in 4-5 different local quads with different setups.

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