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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on my X650's they are shielded, on the F450 its Partially Shielded. but as i read more about this problem, it is an APM problem more than Pixhawk. atleast according to this but the problem does exist on the Pixhawk!topic/drones-discuss/TsuDlbWn_qc

Took the F450 out today, light breeze 2-4 mph. still same drop in altitude  during forward movement. for some reason Drift worked better so maybe i'll just fly in drift from now on

Try 3.2rc2 it s still betta, but so far I was pleasantly surprised, just make sure you read the release notes as the feel of the flying will be different and you might want to adjust some new params to your liking, but overall, on the same copter with the same motors/props and APM it was maintaining alt hold much better.

I have a video from March from my TBS Discovery which show's it holding altitude quite nicely. Skip to 2min 50sec for the Alt Hold section. 

And that was with APM 2.5 with AC3.1, wind was around 5mph.

My thought's are either the foam covering your barometer isn't doing the job or possibly light getting through the case. I use a large piece of dense but still open cell foam as well as coating the inside of the case in black tape.

Hey Mark thanks for the help, i have already covered areas on the APM 2.6 and the Foam is in its proper place. watching your video, it appears that during the ALT HOLD area of that video you are dropping in altitude from a high of 88 meters to a low of 45 meters if i read your OSD correctly? so if anything i will have to raise my altitude to play with alt hold, because i am a n00b i generally try to stay at 10-20 feet. i flew pretty good in Drift mode today so i will probably stay with that more than ALT HOLD until the Full version of 3.2 comes out. thanks again!

Not quite bud, that's the distance from home horizontally. The altitude is in the top right corner and sits around 10mtr.

The only time I'd go up to 88mtr is if I was going fpv lol

Yeah sorry i was looking at the numbers in the top center. i wish mine did that!

I might have missed it but do you have any pictures of your quad?

Just looked at your last flight log and it shows that an Alt Hold your quad is holding within 2 meter's and is showing as climbing when you pitch forward. Though I do note you say you fly at around 10-20 feet so 3-6 meter, have you tried going up a bit higher to see if it still descends or if it's just settling?

@Mark This is a video of my Problem Child

this is the Best i can do to illustrate how the Quads are Flying and whats happening in ALT HOLD. First Video, for the first 3 minutes, i Fly the X650 back and Fourth, trying both ALT HOLD & DRIFT. As you can see by the Vibration graph i am pretty much fine there. DRIFT performs better than ALT HOLD but instead of Descend, it Ascends which i am find with. its a large movement upwards just like in ALT HOLD as it Descends. teh ODDEST thing i noticed on Both F450 and X650, if i fly it in Reverse in ALT HOLD, it stays on a direct line and never Sinks like it does in forward motion.

Videos: X650 FW 3.1.1

F450: FW 3.1.5

Here is Vibration Graphs: X650 Is First,

F450 next,

i will do a Second post to upload logs

Here are my Logs X650 First, F450 Next

X650 Has: 14.7 Props, X650 motors 780KV, 3S battery 800mah

F450 has:  11.7 Props 2212/ 920 KV motors


For the X650, I don't see a problem in holding altitude... errors are <0.2 meters in the beginning and 

For F450 only somtimes the error is as big as 1m, but most of the time errors <0.2 meters when hoovering, even when changing altitude input (climbing).

And <0.5 when moving+climbing

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