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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Loaded 3.3 today, previous 3.2.1 flies fine in PosHold but with 3.3 I got error (Flightmode err 16) and PosHold is not working
Loaded 3.2.1 back and it is rock solid in Poshold.
I did not change anything between the 2 versions
Did this (Note #1: because of the accelerometer range change (see 6b below) this upgrade will require the vehicle's accelerometer calibration to be done again.)
Log from 3.3 attached 2015-04-13 19-18-15.log
Log from 3.2.1 attached 2015-04-13 18-38-21.log

Logs zipped


Loaded 3.3 today, previous 3.2.1  flies fine in PosHold but with 3.3 I got error (Flightmode err 16) and PosHold is not working

Loaded 3.2.1 back and it is rock solid in Poshold.

I did not change anything between the 2 versions

Log from 3.3 attached 2015-04-13 19-18-15.log

Log from 3.2.1 attached 2015-04-13 18-38-21.log


Ok, so Tridge has tested the Zubax GPS and it "works nicely!" it seems so feel free to give it a try and report back!

Thanks Randy. My 4 Year old Daughter is into everything. Have had to lapse a little with playing the devs builds in the park. Have a pix and am looking on adding a second GPS. Maybe the Neo 7 as a redundant backup? Humm..

Great, thanks for the info :-)

wow - thank you very much to all the developers!


Thanks for the tip. I changed aggr to 0.1 and did another autotune. Now pitch seems ok, but roll is still quite bad. Lot's of wobble and quite sluggish. Yaw feels quite aggressive but it works. Oh, when in stab mode and doing yaw, copter gained quite a lot altitude. This didn't happen in althold mode.

new results:

stab roll & pitch: 6.25, 10.95

rate roll



rate pitch










Strangely lot difference in roll and pitch?

log: http://www.droneshare.com/mission/84513

pic of the quad: http://imgur.com/USASeBr

It's 700mm.


Aha, I had forgotten that there's a new CLI_ENABLE parameter that allows enabling/disabling the CLI and in AC3.3 it defaults to zero. Set it to "1" and the CLI is enabled again.

This was done because we found that having the CLI enabled could cause problems for scripts or companion computers talking to the pixhawk as it rebooted. We could default the parameter to "1" but when Tridge and I discussed this we thought that most people were moving away from using the CLI anyway. As far as we know, there are no features in the CLI that can't be accessed through mavlink.

Simple test flight with autotune on Y6B - tuned parameters are not usable - reverted to manually tuned.

What is changed by Autotune_aggr and Autotune_Axes? What are recommended values?


Hi Kuisma,

Yeh, roll is still messed up. The good news is your problem is specifically what the latest changes to autotune are designed to fix. (Rate noise during the test)

To dampen down your Yaw control I would suggest turning on feed forward and using your acceleration parameters. A good starting point is:


If the FF is set to 1 then Autotune will set them at the maximum your copter can handle.

Hi Hubertus,

In exactly what way is it un usable?

Autotune_aggr is a parameter that sort of defines the noise rejection of the autotune. It should have been 0.1. Autotune_Axes is a bit mask to define what axis will be tuned. 1 is Roll, 2 is Pitch, 4 is Yaw, 3 is Roll and Ptich ect ect.

You have the same a similar problem I am seeing with others (but not enough to stop you getting what looks like a reasonable tune) and I hope the next release will fix this.

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