Copter-3.3 beta testing

Warning #1: an issue has been found with Tower's Pause button which can cause the vehicle to fly to an old position if the vehicle has not sent a position update to Tower in some time.

Warning #2: Copter-3.3.2 fixes a bug found in Copter-3.3.1's desired climb rate initialisation which could lead to a sudden momentary drop when switching from Stabilize or Acro to AltHold, Loiter or PosHold.

Warning #3: Copter-3.3.2 fixes an issue found in Copter-3.3.1 which could lead to hard landings in RTL or AUTO if the WPNAV_SPEED_DN was set too high (i.e. >400 or 4m/s) and/or the WPNAV_ACCEL_Z was set too low (i.e. <100 or 1m/s/s).

Warning #4: a bug was found in Copter-3.3 which could cause a sudden crash if you abort a Take-off initiated from a ground station.  Video description is here.  The bug is fixed in Copter-3.3.1 so we recommend upgrading.

Note #1: AC3.3-rc8 corrected a long standing bug in the HDOP reporting.  HDOP values will appear about 40% lower than previously but this does not actually mean the GPS position is better than before.
Note #2: if upgrading from AC3.2.1 the vehicle's accelerometer calibration needs to be done again.
Note #3: set SERIAL2_PROTOCOL to "3" and reboot the board to enable FrSky telemetry like in previous versions.
Note #4: the wiki will be updated over the next few weeks to explain how to use the new features

Copter-3.3.1 is available through the mission planner.  The full list of changes vs AC3.2.1 can be see in the ReleaseNotes and below are the most recent changes since AC3.3.

Sadly this version (and all future versions) will not run on the APM2.x boards due to CPU speed, flash and RAM restrictions.

Changes from 3.3:

1) Bug fix to prevent potential crash if Follow-Me is used after an aborted takeoff

2) compiler upgraded to 4.9.3 (runs slightly faster than 4.7.2 which was used previously)

Changes from 3.3-rc11:

1) EKF recovers from pre-arm "Compass variance" failure if compasses are consistent

Changes from 3.3-rc10:

1) PreArm "Need 3D Fix" message replaced with detailed reason from EKF

Changes from 3.3-rc9
1) EKF improvements:
    a) simpler optical flow takeoff check
2) Bug Fixes/Minor enhancements:
    a) fix INS3_USE parameter eeprom location
    b) fix SToRM32 serial protocol driver to work with recent versions
    c) increase motor pwm->thrust conversion (aka MOT_THST_EXPO) to 0.65 (was 0.50)
    d) Firmware version sent to GCS in AUTOPILOT_VERSION message
3) Safety:
    a) pre-arm check of compass variance if arming in Loiter, PosHold, Guided
    b) always check GPS before arming in Loiter (previously could be disabled if ARMING_CHECK=0)
    c) sanity check locations received from GCS for follow-me, do-set-home, do-set-ROI
    d) fix optical flow failsafe (was not always triggering LAND when optical flow failed)
    e) failsafe RTL vs LAND decision based on hardcoded 5m from home check (previously used WPNAV_RADIUS parameter)

Thanks for your testing!

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          • That's great info! Thank you!  I wish there was more like this in the wiki

            • Developer

              Hi Richard,

              Yeh I agree, but it is hard to do. It took me 10 minutes to do that small block of text, but it would take me an hour or more to write it up in enough detail for the wiki. Then we would need to do that for each particular log analysis.

              The Wiki is constantly traded off against improving the code. If people would like to summarize some of these things and provide text and pictures to Randy we might be able to cover a lot more ground in the Wiki.

              On that note, thanks to everybody that is helping out answering questions here!!!!

              • Thanks for the info (and your time). Great explanation.

                I wish also it could make in the wiki, as it could prevent future crashes...

    • Broke a landing gear doing this autotune test, I will try again but first I need someone with log analysing skills to do a review . Leonard do you have any comment on this?

  • i just had a bad autotune with 3.3-rc7 on a t960 with 18" props and 288kv motors on 6s. Autotune completed ok, but when I went to take off with the new PIDs, it shook violently as soon as it got in the air so I put it straight back down.

    It flew more or less OK with the 'before' PIDs, but was wobbling a bit in a 30km/h wind the other day so I wanted to see if I could get it to fly smoother.

    Param      Before        After

    rate pitch P 0.3    0.49

    rate roll P 0.3       0.47

    rate pitch D 0.01   0.026

    rate roll D 0.01      0.026

    stab P 5              13.1

    rate yaw P 0.3      2.0

    stab yaw p 4         7.6

    Autotune aggr was set to 0.1

    the mot_thst and battery scaling params had also been set for large props and 6s before this.

    The log is 80mb, but it's here if you want to take a look at it Leonard?

    Dropbox - Error
    Dropbox is a free service that lets you bring your photos, docs, and videos anywhere and share them easily. Never email yourself a file again!
    • Developer

      Hi Glenn Henri and Erik,

      How is it all going. Sorry for the delay getting back!!!

      Looks like you have all got it worked out. Let me know if you have any questions needing answering.

    • T3


      the vibes are relatively high as are the IMU2 Acc values. Hence, it might be a vibration issue.

      Best regards,


    • +1 EXACTLY same behavior with same aircraft!

      (Autotune completed ok, but when I went to take off with the new PIDs, it shook violently as soon as it got in the air so I put it straight back down.)

      leonardthal was very helpful and mention that before autotune we should set aggr to 0.05 AND:

      MOT_THST_BAT_MAX, number of cells x 4.2 ==>

      4 cells = 16.8

      5 cells = 21

      6 cells = 25.2

      8 cells = 33.6

      MOT_THST_BAT_MIN, number of cells x 3.5 ==>

      4 cells = 14

      5 cells = 17.5

      6 cells = 21

      8 cells = 28

      MOT_THST_EXPO 0.75 (for 18 inches props)


      So the "violent shook" should not occur IF we start with standard parameter and set the above prior autotune.

      Doing one axis at a time is wise as it might take too long for a single battery to do the 3 Axis.

      (Autotune Bitmask: 0:Roll,1:Pitch,2:Yaw


      7 All
      1 Roll Only
      2 Pitch Only
      4 Yaw Only
      3 Roll and Pitch
      5 Roll and Yaw
      6 Pitch and Yaw


      As for being too crisp after an autotune

      You have 4 parameters you can use to control how crisp it feels.
      If you find it too crips, just reduce ACCEL parameter for the axis you want to make more gentle.

      Hope this helps (all the above were in this thread documented by leonardthal  but 189 pages is a bit long to find relevant info)


      • Thanks for that, what PIDs are you now running with this same craft? Does it fly well in strong wind? I did set the MOT_THST_EXPO and MOT_THST_BAT_MAX params to the suggested values already, just not the aggr.

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Aug 25