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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Too much vibrations on your setup, check the log.

didn't know what was so dangerous vibration, thank

Hi all, I finally got around to giving AC3.1 a good thrashing on the weekend. I put it through about 2 hours of flight time, here's some observations, mostly general feedback rather than support so I'll post it here rather than the forum, though I might follow up on some things there.

1) Two thumbs up for 'Spin when armed'. I was skeptical but after one or two flights it feels perfectly natural now and it definitely does the job of commanding more respect for an armed copter. For example I forgot to hit record on the GoPro before arming one time, usually I wouldn't bother disarming and just reach through the prop area and hit record, but with the slow spinning props it was clear I should shut down properly before going near it

2) And three thumbs up for Auto Tune, wow! I knew I still had some tuning to do on my quad, but never bothered to spend the time learning the arcane art to get the last 10%. After auto-tune it is a whole new beast, *super* tight and responsive and much less wobble on descent. It was a touch too aggressive in pitch so I de-tuned that just a little then pumped up the expo on my transmitter so that my control inputs were smooth again with the much tighter response. It is amazing to be able to click the pitch trim up and down a notch and see the copter flick to a slightly new angle with each click, so tight!

Two little things I noticed though:
  2a) I initially had some pitch trim on the transmitter which prevented it starting the auto tune until I reduced the trim to get back into the deadband. We should add a note about this to the auto tune wiki page. I imagine the auto-tune process could be adversely affected by an out of trim copter too?

  2b) The autotune procedure tweaked my gains accurate to 4 decimal places but I noticed when saving out the config from Mission Planner that it only retains 3 decimal places. I've added an issue to the MP issues list on github about this (

3) Tested DO_LOITER_TURNS and ROI as part of a complex auto mission, they work as advertised, though I was initially caught out by needing a separate ROI command between each waypoint. Although the command is documented that way, I think it makes a lot more sense for it to be persistent as mentioned by a few people here: Though if it were persistent you'd need a way of cancelling ROI to revert to normal look ahead yaw.

4) Tested geofence, it works as advertised, though on one fence break the copter flipped over almost backward and lost a lot of height, almost crashed. Log attached, you can see at line 18122 the pitch goes to 83 degrees and it drops. The geofence ERR message is just before that on line 18100. I tried reproducing that both with geofence as well as by manually switching from STAB to RTL in aggressive forward flight, but didn't see it happen again.

5) A couple of disarm issues/inconsistencies: 

5a) after letting a geofence initiated RTL proceed through to an automated landing and automated disarming, I later couldn't re-arm, and it took me a minute to figure out that I was still in RTL mode. I think it would be better if copter always switched back to STAB as part of the automated disarm routine, to return to a known state where you can re-arm again. Anyone agree?

5b) when you land in an AUTO mission it winds down the props to 'spin when armed' speed but doesn't auto-disarm after 15 seconds. The LAND command is documented that way, but it is a different post-landing behaviour to other modes, and that is more apparent now with spin when armed. I would hope to be able to do a one-way mission where it lands land and disarm safely at the end. Is there a parameter to configure this, or some way of invoking a disarm at the end of an auto mission?

6) New Acro mode is pretty awesome, but I think the default ACRO_RP_P gain should be a lot higher. My first flips were pretty scary as I watched it slowly rolling through inverted even though the stick was jammed all the way over. After increasing ACRO_RP_P to 7 it felt much better and safer to flip. Also, I noticed that when using CH7/8 for the Acro trainer switch it doesn't seem to actually update the ACRO_TRAINER parameter, so you can't refresh in MP and verify you've got the trainer mode set up correctly before using it. It would likely end badly if someone thought they had it in acro trainer mode 2 (limited and self-levelling) when it was actually set to 0.

7) I thought Drift mode would be another simple/trainer mode I wouldn't be interested in, but it was great fun rocketing around without having to worry about keeping your turns coordinated. This is a pretty big deal for newcomers I think - in no time at all they can be ripping around the sky like a pro in this mode. Nice work Jason!


Hi Andrew

With reference to 5b) I found that you need the throttle at zero for the a disarm to occur.

Good luck, sounds like you are having fun though.


Thank you Marco for your reply!

I know that is professional secret! jejeje

I think my multis are well balanced, and I have a external mag with 0-5%compassmot.

I use the standard PIDs in Loiter, and in roll and pitch the custom PIDs (autotune)

The only time I got a similar loiter was when release the version 3.0.1 and kept the loiter pids of v.2.9.1b .... but this is only groping! :(

Hi Marco,

Very impressed with your vids as well, I'd be interested in looking at your parameter list, not to copy as I know that the same performance would be impossible to achieved with a different Hex in more ways than one, but it would be nice to see where you ended up, which maybe a solid way of experimenting along similar lines, even if some of the parameters ended up backwards from yours.

A good educational tool for a lot of us newbs here.


Andrew I wish all wrote experience with APM like u did...

No problem, here the parameters used for make the video of this release with my "HV1 Hexa".
Good luck!


I like the new version.  On my Trex 450 I can take off, go to another point, land, take off again, RTL and land automatically.

It's a little scary to watch because on the first land there was a good crosswind and the heli sat on the upwwind skid for a two second eternity until it decided to take off again.  It did it over and over and I think it's just being smart.

If I put a loiter delay between the land and Take off waypoints,will it sit there nicely until the time is up (maybe even on one skid)? I'm reluctant to try.

Wow... Such a nice review Andrew. Thanks for taking time...

Please let us know about your question in 5b and John L.'s answer to address that.

I never tried auto mission so far and I would like to know if it is possible to shut off the motors completely. I think it is important...

Any video showing APM on your 450 Ray? It has been a while since the last I saw APM flying a traditional heli. I wonder how much they improved on this. Back in days, APM wasn't really stable on traditional helis.

Maybe I should go check the Traditional heli forum:)

It's a little ignored. I don't know why. I'm pumped to put it on my 800mm monster.
That way I can have a cameraship. Although I'm thinking about upgrading to pix hawk.
I'll see if I can video but maybe not since it's forbidden at my military base (deployed).

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