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'm satisfied but just after second autotune The first wasn't good  (autotune>save>autotune>save)

I have large x8  8 kg 


While following the wiki to configure PX4FLOW and Lidar-Lite v2 on AC3.3.1, I am wondering when does the autopilot actually use the PX4FLOW camera. Would anyone mind to let me know if I am right or wrong in the following.

- Autopilot reads PX4FLOW only in OF_Loiter flight-mode? 

- Autopilot reads PX4FLOW in all GPS-assisted flight-mode, but does not read it at all in non-GPS flight-mode?

- Wiki requests EKF_GPS_TYPE = 3 during PX4FLOW test flight. After that I should set it back to EKF_GPS_TYPE = 0 in normal flying?

- Whenever the flight mode requests X/Y position estimation the autopilot reads both GPS and PX4FLOW. EKF then blends them together for autopilot to use?

- OF_Loiter is a flight-mode that needs X/Y position estimation but does not read GPS. It only reads PX4FLOW?

Thanks for clarifying my confusion,


I would say I am right there with you, but you have clearly thought this through more deeply than I have. I am getting ready to mount a px4flow but have not entirely wrap my mind around when OF works and if by using it I loose functionality some where else.

I am interested in the answers to your questions also!

Looking forward to an icon in mission planned to enable PX4Flow as a near plug and play option, with a calibration sequence similar to setting the Acc or compass.

All is good time I am sure.

altitude and current draw log. Are the spikes caused by glitch? my esc's are running fine after the flight


 Do the latest firmwares support V and T setup for hexacopters at all?

@Randy, Paul and the dev team.

Your diagnosis was spot on but took me a while to find.  The picture shows #6 position after landing a 15 minute test flight.  I had noticed this after the first episode but assumed it was from the hard landing, broken landing gear after hex rotated into the ground.  This time the aircraft flew amazingly well until the last few minutes and i initiated an RTL witch it performed quite well and landed within inches of take off spot, only to see #6 twisted over 20 degrees.  Faulty pivot mount on the strut.  I'd call 3.3.1 rock solid to have been able to land in this condition at all let alone in RTL.  Great diagnostics and firmware to match.

Thanks to all


No Witches involved, just poor proof reading.

I'm also completely confused on whether I can use optical flow sensor without lidar or not.
Wiki says it does not use sonar readings anymore and I see flat line for EKF5.meaRng.

Lidar is additional $200...
Lidar lite v2 is only 115.00.


It would be nice to have the option use the installed sonar or lidar, either way OF is really neat feature.


I'm afraid we only support X and + for the Hexacopters.  It's not super hard to add support, just need to come up with the motor mixing for roll, pitch and yaw.

I live outside their country, and shipment to my place is unusually high.

I agree, having such option would be great.

Tried to calibrate OF, but it seems without lidar flowX/Y and bodyX/Y are poorly correlated, scaling will not make them match (bodyX/Y and GyrX/Y do match).

Wil there be ever oneshot support with pixhawk in the future?

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