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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    • Sorry had to repost the vibration test graph


  • Any idea why when the copter is switched in to any mode that requires the baro it has a 1 second full throttle climb then returns back to the requested altitude?  It hovers exactly at mid stick in stabilize.  No expos or anything in tx.  I upgraded from 3.2 per the directions and it started doing it.  I did an eeprom erase and started with a fresh 3.3 rc8 and a fresh parameters and still the same thing.  Log and picture are attached.



    • T3

      A first guess since I currently cannot check your log file: is your buzzer located pretty close to the autopilot - or on the same vibration damped platform?

      Best regards,


      • The buzzer is pretty close but the pixhawk has its own vibration dampening separate from the buzzer.  here is a screen shot with Acc XYZ also.


        • I had a similar issue with the proximity of the buzzer to the Pixhawk. Thorsten and Randy identified the problem (I moved the buzzer a few inches). Note that the problem of interference between buzzers and gyroscopes is being studied. See here:

        • Developer

          I agree with Thorsten that it's likely caused by the buzzer.  At the moment that the vehicle switches modes the Z-axis accelerations on the two IMUs separate.  The MPU6k thinks it's falling, the lsm303d thinks it's climbing.  This is the 3rd incident of this now, makes me think we need to change the tone of the buzzer.


          • T3


            what is interesting is that it seems not to be direct vibration in this case. In one of my logs I saw the buzzer tone in the mag data. So maybe it is magnetic interference. Or sound pressure - which is vibration again...

          • A picture of the buzzer mounting distance from the pixhawk in the attachments.  Its a little disassembled but I'll put it back together the way I had it and test it without the buzzer connected.



          • just remove the buzzzer :) 

            in any case we receive all the relevant info via telemetry either on  MP or tower... 

            after more than a year of using pixhawk I can say that buzzer is more of an annoyance than help. 

            I removed it on the third day and never used on any subsequent  installations.

            p.s. I do not use safety button either :) 

            • T3

              It gives you additional safety. Depending on the telemetry allowed you can have signal loss from time to time. And in this case I am happy about any buzzer response.

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