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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Okay. I think of a simple check whether the deviation of the orientation compared to the last value is too big. If it is too big, it could be compared to the deviation of the other compass. If that one is fine, it should switch to that one and if that's also not plausible (the aircraft can't turn by 90° in 0.1s from one loop to the other (glitch)). A glitch should be recognized and the aircraft should switch to stabilize or land mode.

I also thought, the detection of flying in the wrong direction would be faster. Copter should immediately detect, that it is flying further away from the desired position (GPS) and there should be a failsafe triggered.

But maybe just everything happened too fast..

Yes, I have only 1 external GPS with integrated compass attached (Drotek M8N XL).

Hi Randy,

Can you please look at my log, and posted compass issue reported few days ago?

Link to the post


I made larger flights with new release with FPV and notice that some times, when I was in pos hold and pitch to start the fpv fligth, pitch react more violent than usual but them the fligth was normal, I remove the gimbal and the issue stays there but not always, that's the strange, I download the log and notice that pitch didn't track desired one 

Any idea what happens?

I only notice the fpv camera loose, It's possible the cause?

FnoopDogg, yes, switching back to AltHold or Stabilize would have allowed the pilot to recover.

Any suggestions on improving noisy IPD EKF values? It appears that it is mostly related to a Noisy Barometer. I've got vibrations well below acceptable levels. 

The Pixhawk is housed in an rctimer dome.

I loose about 5-10 feet of altitude transitioning from hover to directional flight. I've increased EKF ALT Noise to 3.7 and its subdued the rather aggressive drop to a sustained slow drop over about 10 seconds vs 1-2 seconds.

Still would like to improve on this.


did you foam the baro? Yes even with it in a case and yes even with the RCTimer AVDome. I had similar issues with one of my hawks and it too was in an AVDome and some dense foam and a recalibration did wonders.

Also did you make sure to adjust Hover_Throttle to match exactly what your STAB hover is in mission planner? 

BTW Tlogs are pretty worthless. You need to attach an actual .LOG/.Bin that you download from your Hawk.

It is a 3DR manufactured Pixhawk. Opening it up and adding additional foam was my next idea. It remains in the 3DR case under the dome.

How do you recalibrate the barometer?

I meant ACC and MAG as I don't know of any way to calibrate the baro.

I think it does that itself at every reboot. 

Kenneth: I had the same issue with vibs under acceptable levels during long time but vibes were my problem at the end, be shure that isn't the problem.

Sloppy motor bells can also cause some of these issues.

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