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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    • You were right, here is the correct log, which shows information that matches the behavior seen in the video.

      I am really sorry. That should not have happened. The timestamp of the video was wrong so I focused hard onto the wrong log..

      Thanks for looking into it again. Hopefully we can find the cause now.

      2015-11-21 14-41-31.log

      • Developer

        Hi Dave,

        This is an unusual log. There is no obvious motor sync issue or any sign pointing to one motor being lost. The closest to this I can see is that Motor 1 appears to be working a little harder than the rest but this is probably just due to an offset CG or that motor having a slightly lower kv than the rest or something similar.

        What this looks like to me is one of your motors has rotated during the full throttle burst. This has then caused a yaw that the controllers are fighting by dropping motors 3 and 4 to minimum. The thing that makes me think that this is the case is that motors 1 and 2 are almost equal suggesting that neither one is bad.

        If you have a single motor out situation then you normally see loss of roll and pitch control with a single motor going to maximum.

        When you looked over the copter after the crash was any of the motor mounts able to rotate on the arms or needing to be straightened. There is a 1 in 4 chance the motor that rotated is also the one that broke in the crash.

        Does any of this match what you saw in your copter as you fixed it?

        • I tried twisting the mounts and it was impossible to turn them (it was also impossible to turn the mount that got twisted (see photo on the tree stump) in either direction). I really applied a lot of force while my brother did some shocks with a little hammer. if any of the mounts would have been loose, we would have discovered that.. the flight Controller is also fixed. 

          also the broken off mount was still in its place (could see that while looking at the remaining plastic part). 

          what could be: it was cold that day (around 0°C)  and maybe it was easier to twist.

          will put it into the fridge and try again. 

          • Developer

            Hi Dave,

            So this has got me puzzled. We have Motor 1 going a little high for a moment during the full throttle burst but nothing too major. Maybe enough to suggest that the problem may have started there.

            We see the negative yaw rate error starts we also see a small positive roll and negative pitch angle error appear and go away. This initial deviation suggests a loss of lift from motor 1.

            This is where I would normally expect to see all other motors go low and the copter flip roll positive and pitch negative with a slight negative yaw. However this isn't what happens (obviously).

            So the copter does something very strange at this point, it hardly loses roll and pitch control at all and instead starts to spin in yaw (negative) with both motor 1 and 2 high and 3 and 4 low. This is very unusual because motors 1 and 2 have very similar outputs and they stay that way all the way down.

            Looking at the logs I see two possible causes of this combination of events.

            1. We have partial failure of lift on both 1 and 2. This may be sync issues, loose props, interference on the esc signal line, ice build up on the props (thanks Martin)..... Any other ideas.....

            2. One of the arms rotated in flight. Because motors 1 and 2 have the same output and we expect to see a lost of lift from a rotated arm, that would suggest motor 3 (being higher than 4). You have already said this doesn't look like the problem unless the cold allowed them to move. However, you should have been able to see this on the copter after it landed.

            What arm broke?

            This really has me stumped....

            Looking at the video it looks like there is some serious vibration as you go full throttle and the initial yaw rotation looks almost violent and there appears to be a shock go through the frame just as it happens. Looking at the vibration logs you can clearly see this too. Vibrations steadily increase from the moment you go full throttle as the motors spool up (you can hear this on the video). Then BAM there is a massive amount of vibration just as you loose yaw control. You are getting clipping in the accelerometers meaning you are hitting 16g. Your climb rate reaches 3g so your copter is putting some power down during the climb.  So this is definitely pointing to a serious mechanical problem. So maybe the person suggesting your arm broke in flight rather than in the impact was correct. It may not have been a full break and instead twisted partially in place causing the yaw rotation.

            Any more information you can think of??

            • Hey leonard, sorry for the late answer.

              please also read the post I made above (here:

              the arm that broke is arm 2 (rear left).

              To your thoughts at 1:

              sync issues were tested at my bench and I didn't find anything unusual :/

              Ice could have been at the props but if so, it couldn't have been much, as I didn't fly high before the throttle burst.

              Also I put circuit board paint at my ESCs to protect them from any water.

              interference on the signal line could have been there, but I don't think, that could be the cause for that sudden failure.

              See the above post for information regarding your second point.

              One arm was slightly rotated after the crash (maybe 3-5°) but as I said, I couldn't move it afterwards. It must have been from the hard crash.

              I have no idea what caused the vibrations :( maybe I just have to live with this not understandable crash of course mostly because the copter was too far away to see the decent good enough to see any breaks :/

            • Are the arms "pultruded" or woven carbon fiber? I've had pultruded lose torsional rigidity after a crash with no apparent loss of longitudinal strength. Longitudinal delamination of fibers allowed the motor to rotate very easily about the longitudinal axis of the tube...unflyable, yet no apparent damage... FWIW.
              • @mike:

                the arms are very stiff. however the folding mechanism could be the weak point which allows vibrations to occur.

                • Forgive me if this was already discussed pages back but... could a prop have come only partially loose? It could cause high vibration and noise. 

                  Another off the wall possibility is perhaps one prop caught something like a feather that of course fell off on impact so you never knew it. LOL yea I know..... suuuuuure that's it. 

                  • Props were still immovable after the crash. I tightened them strong enough and there are also locknuts being used. So I guess it was the feather :P

      • Developer
        Thanks Dave,
        I will have a look as soon as I get home.

        And sorry for the capital letters.
This reply was deleted.


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