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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I want to follow up on this, in regard to my Pixhawk having abrupt changes in course when in GPS modes. Based on analysis of logs and suggestions for different configuration and some shielding, it now has much better performance. The copter now has the 1.3GHz vtx antenna on the bottom, with foil shielding on the video signal lines and covering the single-board camera. The logs now still show drops in number of sats and peaks in HDOP that look similar in shape to before, but the numbers are better, so it doesn't seem affected by them. Number of sats was high of 13 with drops to 9, now highs of 15 with drops to 13. HDOP was normally .8 with spikes up to 1.2 and now levels out to under .7 with spikes up to a max of .8. Thanks to Andy, Derek, Vesselin, Ivan, Cala, and DG for the diagnostics and excellent suggestions. My confidence is much higher with this platform now. It takes a village...

Sweet! Glad you got it sorted.

I think this kind of story shows just how vunerable GPS's really are and just how much the FC is using it. I had no idea when I first got into this. I'm also amazed how much difference shielding makes - its so much more convient than distance!

FWIW looking at your photo again, I have discovered that the cable end of LiPo batteries give off a lot of magentic interference and now mount my batteries with the cable end as far away from the compass as possible. I suspect you have enough distance for this not to matter, but FYI.

Sorry to barge in and this has probably been discusses a thousand times 'somewhere' but do you think it's advantageous to put copper foil tape on the bottom of a gps case? I have the typical black round plastic gps case on a mast. Would copper tape on the bottom be a good idea? Seems a but less messy that copper foil on all the wires. Thoughts? Thanks 

I put cooper under gps on my last build, It's changed from 10-12 sats to 18-20 sats :O and I don't need a tall mast, only a second floor over the Pix, I connected the cooper to the pix with a ground wire.

So I've always been suspicious of this since I'm pretty sure every GPS has a ground plane anyway. I think the EMF interference is a field rather than unidirectional, so you'll be missing some of the radiation this way. That's why I think identifying the sources and shielding them is more effective.

But Cala's experience shows that it still works pretty well!

copper base helps a bit. but what helps way better is to use properly filtered 5V voltage feed, from a BEC separate from the one that feeds flight controller. when i rerouted power and stopped using 5V from the COM port where GPS was connected to quality of data has improved tremendously, as well as speed of sats lock. 

I'm a bit confused lol.  Do you mean AcHlt and GyHlt?  If that's the one, I'm getting a drop from 1 to 0 on GyHlt from IMU2 every few flights.  Also, anyone know what this "ERR: 195-129" is?  


hi randy and all friend.

My hexa is problem with speed up when  i push little thorttle up or down with YAW, then my drone speed up or down very fast, just alittle about 30cm.

My drone : 3DR pixhawk, 3dr gps lea6. KDE motor 475kv, esc 35A+. props 14.5, battery 6s 6.000mah, total weight almost 4kg.

ffrimware 3.3.3 i have try with autotune 3-4times but the pid look bad. can't fly with that pid. i have manual setup and it's look good abit, but with the post hold mode, when i push pitch or scroll and stop then my drone is oscillate, not smooth, but with loiter mode or alt hold work good.

Please give me an idea. Thanks all

this pids after autotune.

Pids are not bad, but stabilize pitch/roll params are usually not more 8. You can try manually 5; 6; 7 etc.

The reason for Yaw and throttle height variations is bad barometer ventilation. .Will be good to send picture of the copter and the Pixhawk position.

It is important to make the barometer damping with dense polyurethane, proposed by Marco and I posted here:


Then should avoid the air stream from the propellers direct to the controller - can try kind of windshield, box with some side holes only or similar. When launching / landing the air pressure area below the copter can cause jumping, if barometer not damped.

Black Sheep (who I bought the pixhack from) says it interference...  Really?  Not the best answer.

Can't remember where I heard it or if its true, but something about the gyro does an internal calibration on power up and if the copter gets jostled during this time (like plugging in a xt60 main battery connector) it can throw this error. This would be different than the flashing red/blue partway through the pixhawk boot. Again not sure if accurate, maybe someone with the hardware knowledge can chime in.

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