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


      Thanks for the report.  It's best to include a log.

      Without a log, my guess is that it's a ground station issue because the Copter flight code never deletes mission commands.

      Make sure you're using DO_SET_ROI commands and not NAV_ROI commands (NAV_ROI commands should not even appear in the list of available commands unless the GCS is out of date).

      • Thanks Randy, sorry I forgot the log here it is log. I tried with MP stable and latest beta without luck. Added the DO_SET_ROI command after first waypoint.

        2015-07-17 22-31-00.bin
  • Not sure if this is 3.3 related, but my copter flips when landing in loiter.  I didn't notice the issue before 3.3... It happened occasionally, but I was always able to blame a hard landing or something.  Now it's every time..   It's like when it hits the ground and stops moving, the copter speeds up the props..  Then even w/ 0 throttle the props keep spinning and it flips, and the props keep spinning, until I put it in stabilize.  I got in the habit of quickly switching to stab just before landing, but forgot today, and it flipped and broke all the props :(.   Expensive mistake (t-motor brand props :( )
    it's a 650ish size quad, 16" props, lots of power. 

    If it would detect it's not descending anymore, and detect it has flipped over, and immediately stopped the props, there wouldn't be so much damage..  But as it is, they just keep on spinning and shred themselves on the ground. 
    I know I can switch to stab,  but in a panic, sometimes it's difficult to remember procedure.

    I'm still on rc5.

    • Developer


      The landing detector has changed a bit but generally it should be working better than AC3.2.1.  If you have a dataflash log of a couple of landings that'd be a great help to finding the cause.  -rc5 and -rc7 should act the same when it comes to the landing code except that the crash detector is better so the vehicle should always end up "landed" or "crashed" now.. previously it was possible to get stuck in a state that was neither and the vehicle could thrash about for a while.

    • I think it got fixed in rc7 as I had same thing on rc5 in RTL and now it just stopped happening, with flip and killing grass.

      do a new function 31 to kill motors on some side switch on your transmitter to be able to kill motors instantly - but I noticed I keep my finger at that trigger at landing but it now lands smoothly and just slows down props - but not shutting them down or disarming, so then I hit motor kill switch and it disarms.

      but it is not doing 'hopping dance' after touching the ground anymore, may be due to dual gps units and better setup with less interferences so it is more confident of its landing coordinates than before.

      • Thanks, the motor kill switch will be a prop saver, for sure.
        As soon as rc8 comes out, I'll upgrade and recalibrate everything and start testing again.

  • I did a range test today and noted that in position hold at maximum speed drone starts to drop altitude very fast sometimes, will look at logs later today, but, it probably would worth to have some checks in there to control movement speed and recover angle of attack a bit if drone is dropping down fast - like when it is 700m away and you cannot really see it and want to bring it back faster. at RTL mode it was going 16 km.h fine maintaining altitude, but at 66 km.h in manual mode it was not able to sit at same height. so may be it would be ok in stabilize or acro for it to drop but in a 'smart' mode it probably would be better to have some safety net and limit this vertical movement down to 2m max and then adjust speed to make drone able to recover altitude. 

    • Developer


      Yes, we've had some requests to prioritise altitude over lean angle in AltHold, PosHold and Loiter so I've just raised an issue for this enhancement request.  Leonard and I actually have a patch for this but it leads to some bobbing up and down as the vehicle reaches it's limits.  Current the patch is only for Loiter and AltHold and it could be extended to PosHold but first I'd like some testers to confirm they're ok with the bobbing.  If I make a patched -rc8 would you be willing to give it a try?

      • Hi Randy.

        Just for information: 

        1) On a small 500 Quad, I could see the lost of altitude in AltHold going forward. The curious part is that stopping the forward motion the Aircraft is regaining altitude!?

        2) Same 3.3 RC7 on a medium size hex (960mm) no loss of altitude using AltHold.

        Not sure if it is relevant or not.


      • This is also an issue for me when using the copter (Y6B) for aerial imaging. When it flies against the wind it sometimes comes to its limit for attitude control (especially yaw), because one or more motors come to their upper limit. Until now i help myself by

        1. reducing ANGLE_MAX in parameters
        2. changing wpnav_speed via RC6 depending on pitch angle from telemetry

        It would be helpful to have a separate ANGLE_MAX for AUTO/POSHOLD/RTL

This reply was deleted.


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