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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Leonard, this was something i was not knowing. Activating ATC and FF will be considered during autotune and set to max the copter can handle ? if it's so this is pretty cool!

As i'm flying almost acro i haven't enabled ATC and FF but considered the benfits i'll give it a try....


tried again flying with the autotune parameters - it´s flyable, but there is some overshoot and oscillations in roll. Rate P/I pitch is out of range according to MP - is this a problem? Response in pitch axis is quite good, so perhaps i should leave it to the tuned params.

Randy you're right, what i used it for is in the Mission Planner in the Register "Terminal" to download the logs to my computer (usb) or to enter Setup for reset.

Starting from 3.3 after connecting to pixhawk a message "Port already open" was shown.

I'll try it out if its better by setting CLI enabled..

Nice to Know Chris your continued support for the APM 2.6. I have been very pleased with the performance one my TBS quadcopter using AC3.2.1, no issues perfectly works well with sunnysky 800kv motors and my flashed 600hz esc Simon K. It bring the 8bit apm to life, even in gusty wind i still enjoy the ease of flight. I shall take the step towards pixhawk, just a couple of more moths till the firmware is well tested.

And congratulations on the 3DR Solo, amazing drone, seen your videos. Solo name suits it perfectly i would say, single pilot for camera and drone. No need for for second operator or second remote. GREAT WORK!!!!!

Hi Hubertus,

Oscillations is definitely bad. But it is strange as tuned pids seem to be more conservative than your original pids.

If you could try the autotune in the next release for me I would really appreciate it!!


Perfect, what are the parameter changes needed?


Cool, Thanks Pomaroli!!

I will be very interested to hear your feedback!!

With the next autotune, I hope you will get a nice tune and close to maximum acceleration parameters.

"support do-set-home command (allows return-to-me and locked home position once GCS enhancements are completed)"

Can somebody provide some information on this specific feature above (10.a)? Is this implemented and its currently usable? If not, then when will it be available? 



I connected my Zubax GPS, LEDs on the zubax are lit but I get no GPS signal through to the Pixhawk or indication in APM Planner.  I can't find anything in the parameter list that looks like a UAVCAN parameter or to direct gps signal.

Hi! How many minutes does autotune require to complete the entire cycle? I am having a hard time doing so since my flight time is just 7-8 minutes with my current setup.. I always end up landing the quad due to low voltage...

Hi Erwin,

I am glad you asked :)

AUTOTUNE_AXES controls which axis is tuned.

1 is roll

2 is pitch

4 is yaw

So then you add them if you want to do multiple axis so

3 is roll and pitch

7 is roll, pitch and yaw.

So do one axis then put a new battery in and do the next axis.

Let us know how you go.


Yesterday I installed AC 3.3 rc1 and today I ran Autotune. The result is not good, there is some overshoot, the yaw jumps.. Adds a log of my flight
best regards


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