ArduCopter-3.1 released!

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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  • Finally got to try this out today - autotune worked great, loiter is very solid and drift is going to be a real hoot. Excellent work by all. I can't wait for warmer/drier weather to really get it out to stretch its legs.

  • This was a very bizarre and potentially dangerous incident. The quad in question is a QAV500 with an APM clone running 3.1. I've run RC-7 on it, no problem. Two days ago I upgraded to the full 3.1 release and it was fine. More than fine in fact, it was excellent. Can't say enough nice things about it. Tried Sport Mode and a Loiter takeoff. It's been Autotuned and holds a solid loiter in the wind. Drift Mode is a blast. Excellent. This is my solid aircraft of the several I own, all APM powered. Afterward I downloaded the flight log to check the current use with the new APC Multirotor props. Made no changes whatsoever. Flash forward to this morning.

    Took the QAV to a large open field for its first flight of the day to try Sport Mode more and was going to do a Loiter takeoff. External LED was solid blue, showing GPS lock. I had a ground station running and it and Mavlink/MinimOSD also showed GPS lock.

    Put it in Loiter mode, armed it (flashing red LED went solid) and started raising the throttle. At about half throttle the QAV did a violent flip on to its back, motors running hard. I was momentarily stunned and then shoved the stick to do a disarm. The motors kept running. I tried toggling my flight mode switches and working the disarm more. The motors kept going. The external LED was flashing red, indicating it was disarmed but the props were spinning like crazy. Hmmm...Didn't look disarmed to me.

    Now that was weird, but it gets stranger. I looked over at the ground Station display for a clue as to why it wouldn't shut off. The Flight Mode entry where it normally displays Stabilize, Loiter, RTL, etc, was blank! No entry at all. Never seen that before. But the display was showing changing values for current and other parameters, so I had a connection with the APM.

    I hurried over to the QAV and the motors were still going good. Since it wasn't responding to my RC transmitter I couldn't see how to shut it off short of unplugging the battery. And the battery connector is VERY close to the spinning props.

    I have skids on the bottom of the QAV which turned out to be excellent hand holds. I picked it up like a snake about to attack. As I rotated the quad different motors would start spinning as some sort of response to its attitude. There really wasn't a point where I could get them to all stop. I know 3.1 is supposed to have automatic motor shutoff, so despite the fact it had already been inverted on the ground I tried holding it upside down for a while, but I think that just pissed it off more.

    Sometime during the commotion I saw the prop for motor #4 had departed. I was able to find an attitude where I could get another motor to temporarily cease spinning which gave me a window to reach in and unplug the battery. Short of holding the damn thing until the low voltage cutoff hit, I don't know what else I could have done.

    I took off the props, or what remained of them and plugged the battery back in. I got a GPS lock and armed the QAV. Red LED went solid. I moved the stick up and only three of the motors responded. When I gave pitch and roll commands the proper motors did not respond. It almost seemed to be acting like a tricopter, but not quite. When I picked up the QAV and tilted it, the motors sped up and slowed down in a nonsensical manner. I then disarmed it (solid red LED went to flash), yet the QAV's motors would still respond to the throttle!

    But wait, there's more....As you might imagine, I was just a little bit interested in looking at the logs. They don't show a Loiter mode at all. Only Stabilized, which I didn't invoke. I had 6 satellites at all time ( I would have sworn the Ground Station showed 8, as I'm sorta careful about that stuff, but OK), yet a GPS glitch was invoked. The crash detection went off multiple times ERR 12), which is good, but the damn motors kept going. Does motor shutoff on crash have to be enabled?

    The logging ends rather quickly, which would be consistent with a quick disarm on my part. But that SHOULD have cut the motors. There is nothing in the log's roll or pitch data that showed me moving the quad around in an attempt to shut the motors down.

    Curiously, there are only three throttle in entries, matched by identical throttle out entries. 80 then 119, then 119 and back to zero. It takes about 450 to lift so it shouldn't have gone anywhere.

    So....WTF?? I'm OK with the very occasional "crap happens for no good reason" sort of incident. It keeps me humble. But the motors not shutting down was extraordinary. If that prop on motor number four hadn't come off I don't know how I would have been able to reach anywhere near the battery connector with a very live and angry bird.

    I've attached the log for your amusement and review. It's pretty short. I might be able to buy a GPS glitch causing a problem but it was an exceptionally violent flip. Should I consider erasing and reflashing the EEPROM? Or should I instead hire an Exorcist?

    2013-12-17 17-18QAV crash1.log

  • After update (and cold weather):

    Also some problems with parameters in beginning, some defaulted when connecting to MP, some not. Resetting helped.

    after PX4 combined with 3.1fw makes me crazy, MP shows slowly accelerating vertical velocity in table test. It starts slowly (positive or negative) and then diverges faster away from 0 altitude to eternity?

  • MR60

    I have a question about new parameters since 3.0.1 that I upgraded to 3.1:

    -MOT_TCRV_MAXPCT : i see "93" in the value column, while it is indicated "20  80" in the options value (min, max I suppose?). How was this 93 value fixed as this parameter did not exist in 3.0.1? Should I reduce it then to 80 ? 

    Thx for advice

  • Developer


    My "kamikaze hexa" with "2814 710 Kv" motors (a lot of power with 6S LiPo), Pixhawk V2.4, U-Blox GPS with built-in compass and the new boxed 3DR Radio, ready to takeoff for another video with APM Copter V3.1 (with some acro maneuvers).

  • Did Loiter turns/Circle get fixed in this release? or is that still waiting on 3.2?

  • Ready to load up and test this version out, thanks to every one working on this project!!

  • A big thank you from Cologne in Germany for the great work on the software.

    Everything works perfectly in this great project.

    Allen "pilots" a great Christmas and a happy new year.
    Happy landing, Klaus

  • I have a question:

    What exactly does Load IRIS Defaults  do at AC3.1 ? Only changes RC Setting (Flight Modes) or does it change sth else ?

    Is it recommended to use the defaults at older PIXHAWK hardware revisions (<2.4 ) as well ?

    Loiter works great,btw.

  • MR60

    @Marco, in your Tx switch config, you have six flight modes configured on two position switches, but then you said you also configured "simple flight mode" on a third switch? How do you configure this 3rd switch to trigger simple mode? (And thus override the currently selected mode?)

This reply was deleted.


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