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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      • T3

        Yes, the accel values look very good but the vibes are relatively high. 

        Adolfo, can you make s short test with IMU_RAW logging? I am really interested in this because the vibration on my copter seem a little higher compared to yours but the vibes on my one are much lower. Maybe a FFT analysis can provide some insight.

        Thanks and best regards,


        • Here you go.

          First couple of minutes it is hovering in the same place. Then you have some really easy flying in poshold and then some really hard poshold flying. You also have some full pitch forward, full pitch backward and also full roll left and full roll right.

          Do I need to worry about something or are my vibrations safe ?? To me it flying well. I don't know more to be able to spot if something is wrong.

          Thank you








          • T3


            thanks a lot for testing! 

            I just had a very short look. It seems you enabled IMU_FAST instead of IMU_RAW (because I could not run an FFT in MissionPlanner).

            What is really interesting is that the Vibes closely follow vehicle movement - although the idea behind is to "remove the vehicle’s movement and create a “accel_vibe_floor”. This is visible in my logs as well to some degree but your flight was longer and maybe much more aggressive.

            Could you please try again with raw IMU logging? 

            Thanks again!



            • Didn't Rob explain its supposed to be like that? They are accelerometers after all and I really pushed the hexa to the limits so they are measuring the actual aceleration during maneuvers. The "grass" height is actually very consistent and within the range.

              I had both enabled. Fast and raw. Tomorrow I'll give it another try if the weather allows it. It's night atm.
              • T3

                Hi Adolfo,

                maybe Fast and Raw are not working in parallel. If Raw is enabled Acc1 and Acc2 are logged not IMU1 and IMU2.

                Regarding the "grass" vibrations seem to be no problem on your setup. However, I would appreciate if you could give RAW (only) another try. Just a short non-aggressive flight :-)



                • Tell me exactly what you want me to do during flight.

                  Another 2 min of loiter in the same spot and some cruising around again in loiter ??

        • Yeah, I've talked about this before, we need to have a better understanding of what we're seeing in the data.

          My gas helicopter has really high vibration visible on the IMU.Accel logs, but the Vibe analysis shows the vibe levels very low. Leonard says this is because the Vibe logs show only high-pass filtered logs, so my gas helicopter has only low frequency vibes.  That makes some sense, because it's got a really good physical vibration isolation system.

          • It is an interesting topic, those vibrations. Both vehicles i have now have very little level of motor/prop vibrations under calm no wind conditions but i noticed when i get small one up high enough and it starts adjusting position to counteract even slight wind i get a period with a lot of instability. I wonder what variables dictate level of aggressiveness for those corrections so i could try to adjust that.
            It can also be seen in circle mode if i take a video - at some angles during rotation everything is smooth and nice and then at some angle it starts to shake hard enough to get jello all over. It does not seem to be normal, and it seems definetely related to a certain yaw angle relative to the wind direction.
            I will try to replace props next week to see if that will help but it would be great to learn what else can be adjusted in parameters to smooth up transitions.
            It is important to note - at low altitude it is as perfect as can be in all modes and all angles.
          • But it's not clear to me how you can have low vibes in the Vibe log, but high vibes in the IMU.Accel logging.

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