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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            • Developer

              It was a while ago but I think we discovered that it was an error in the log analyser - it was looking at the wrong bit perhaps because of an ardupilot software update that moved the bits around in the dataflash message.

      • Developer

        Hi Paul,

        The Yaw autotune is more aggressive now as we were getting very low values on the ATC_Accel_Yaw and the result was very slow yaw response. The downside of this is that high powered copters can give a little jump on each autotune test or when applying yaw.

        The solution is to reduce the ATC_Accel_Yaw value until you don't get a jump anymore.

        • I confirmed what was the issue with jerky yaw. I flew yesterday on the single glacier 45C pack, 5000mah.

          today I loaded double pack and did autotune this way - and it completed perfectly setting drone to the optimal attitude, it is as smooth as it was before.

          I guess when it is underloaded, with 6 4006 620kv motors it is too much thrust for autotune to generate best results.

  • Connecting power to  pixhawk with 3.3

    My quad has the lipo and power connector at the bottom of the quad, meaning I have to turn the quad 180 degrees for connecting the power en then turn around and put on the ground

    Can this be done wile the pixhawk led is white or is this a nogo situation?

    when is the sensor calibrating starting when power is connected?

    • Developer


      The critical time is when the LED is flashing red and blue.  That's when it's doing the gyro calibration and during that time the vehicle shouldn't be moved.

    • Until 3.2.1 is calibrated when armed; I didn't read that this change to 3.3

  • Auto-Tune fly away.  I just completed a fresh build 960 hex and have flown it several times on rc7 with very good performance in stabilize, loiter, alt hold, land and rtl.  The vehicle did not exhibit any problems at all, in fact it flew remarkable well with default PID's.  It remains a question why I even did an Auto-Tune at all, but that is where it all went wrong.  It did the initial twitch right and corrected then twitched left and drifted off about 10 meters, then rolled right and flew off about 30 meters before I switched off AT and hit RTL.  It came back without a hard landing but this is my first shot at a heavy and it made me pucker a bit.  If someone could take a look at the log I would appreciate it, I'm a little nervous to take it up again until I understand what happened.

    Thanks, RB

    • Developer

      Thanks for the testing and report, looks like Leonard and Artem have it covered so I've only looked at the logs briefly... just as a side-note, I probably wouldn't call this a "flyaway" as such.  I'd probably call it a "temporary loss of control".  The meaning of the term "flyaway" is evolving a bit but my personal view is that a "flyaway" involves the vehicle being out of the pilot's control (for whatever reason) and flying far away, perhaps out of sight and then crashing.  So I think if you recover the vehicle and land it safely it's technically not a flyaway with this definition.

      I don't want to promote a big discussion on what is a flyaway although I can (or someone else can) create a discussion for that if people do want to discuss the meaning.

    • Developer

      Hi Randy Bachtell,

      It looks like your down going motor is unable to start again after the twitch. This can be caused by setting your Thr_Min too low. As Artem said, it can also be motor sync problems but lets hope that isn't the issue.

      So I would suggest that you increase your Thr_min until your props are spinning assertively when you just raise the throttle so the motors come out of spin when armed.

      The other thing to point out is that in Autotune you are actually flying in Alt Hold at all times except the little twitch. So if you can have a problem in Autotune, you can have it in Alt Hold.

      • Thanks for your help, unfortunately this time it ended in an uncontrolled roll. Crashed and burned resulting in a complete loss of the vehicle. I may be able to recover the card from the charred remains if you think it could be beta material, otherwise I will lick my wounds and stick with my smaller drones. I did some very aggressive roll maneuvers right and left in alt hold before switching to Autotune with no problems. It tilted about 45 degrees both directions and immediately leveled out with stick center. AT resulted in the death roll on the first right twitch.

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