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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 Noticed also that terminal connection thru mission planner is not working properly, after connecting it's saying always "opened Com port".

I will upload the logs later today. I have one more question... Can I assign another channel other than 7 to trigger the camera? I actually want to trigger 2 cameras. 1 on channel 7 and one on channel 9-12. I recieved a stratosnapper that does not work. And do not have time to wait for another one.

Thanks again.

Is the increase in the number of Do_Jumps permitted from 3 to ? included in this release?

I second that. I too have been patiently waiting for UAVCAN on The APM side. QGroundcontrol is much more user friendly after the latest upgrade but still a bit awkward IMO for flight modes. You can try out your Zubax gps with QGC if you are flying a quad as they have an option for UAVCAN in the frame setup.
I will be testing 3.3 next week. Thanks Randy and team for all your hard work.



DCM is still there as a backup for attitude estimation (roll, pitch and yaw/heading) but for position estimation EKF is the only option now (i.e. inertial nav has been removed).  The EKF is better at detecting and dealing with sensor failures (i.e. GPS & baro glitches, bad compass alignment) so it may be a real problem that the older system simply couldn't detect it.  That's a guess of course, we'd need to see a dataflash log - Paul Riseborough (EKF expert) could have a look I think.


Rob Lefebvre is working on this and although it's not in this first release candidate I think it will make the final release.


At the moment, it simply sends angle demands to the gimbal via a serial interface (we need a wiki to describe how to connect the serial cable and also not all alexmos gimbal control boards expose the requierd pins).  In the first stage it's not too different from using a pwm interface although the setup should be easier.  This release also adds support for the do-mount-control mission item so besides ROI, a camera can be pointed to specific angles as part of a mission.


We only support triggering a single camera at the moment.  I've created an enhancement request here but I can't promise when we will implement it.  You're actually the second person that I've heard ask for this (although the other person wanted both cameras to take pictures at the same time).


We have some UAVCAN support in this release including support for some experimental UAVCAN based ESCs.  Tridge is the one who has been testing out UAVCAN for other sensors so I'll ask him about the UAVCAN GPSs.

Hi Kuisma,

Definitely a bad tune there and I already have some changes for the next release candidate. I will check over your logs and get back to you. I would switch back to the old parameters.

I can't seem to access your log file. If you could make it available that would be great!!

Hi Pormaroli,

The tune on roll looks a bit suspect but pitch looks ok. Can you provide  a log?

@Craig DeFleming

First Issue: It's takes a few seconds for the EKF to start functioning. The BAD AHRS warning should always clear itself momentarily on the HUD.

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