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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these threads are always long and hard to sift through if you are looking for something specific, but that applies to all forum/blog type discussions. I personally don't think the release cycle is that long given how many new features are implemented. Also compare to some other open source projects which normally are a right mess of code and bugs. In this regard APMcopter has come a long way in the last two years. If you don't want to risk testing betas, stick with the old stable version and wait. I found, especially with 3.2 and 3.3, that I could fly all release candidates without being overly afraid of bad things happening which was not always the case in the past. So I think the dev team is doing a really great job here!


Since the Wiki doesn't fully explain how to use the Auto tune in 3.3 could you please explain some things.

I understand that it is a flight mode and needs to be entered from a single switch throw from AltHold?

How does one save or discard the Autotune?

What is the suggested starting value for Autotune_AGGR.  I have seen some using .10 and some .05; is there no in between?

Hope to try this out on my deadcat  tommorow.




The wiki pretty well covers it.  I don't know about Autotune_AGGR though.  It recommends a range of somewhere between .10 and .05 though.


After autotune is completed:

Land with autotune on and the settings are saved.

Land with autotune off and the settings are discarded.

Note that mission planner will tell you, "saving autotune".

As for aggr..  Still not really sure.  I know that at .1 my copters are pretty skiddish.  At .05 they're doggy lol!  I need to do more testing.  BTW, all my copters are 960-1300mm hex and X8's.  Not to mention 7 to 18kg, so my findings probably don't mean much.


The wiki makes no mention of autotune now being a flight mode it still makes reference to ch7/ch8 so I don't think it covers it very well. 

 This information may be more accurate but I can't confirm it. 


So it would be nice to hear the definitive answer from one of the developers.


When you say land does that include the requirement to disarm to initiate the save?


Yes, you'll need to land and disarm while still in AutoTune (i.e. ch7/ch8 switch high or flight mode set to AutoTune) to save the gains.  I've slightly updated the "Changes for 3.3" section of the AutoTune wiki page.  Hope that helps a bit.

Certainly we need to add the ability to start/stop/monitor AutoTune from the GCS in future versions of the software.

First practically trouble-free flight with v3.3rc10, an AUAV-X1 flight controller on a small carbon tricopter.

I did notice however that I could arm and fly without a GPS lock at all despite ARMING_CHECK set to 1 (enabled), is this normal?

3.3 RC-10 on "true" Pixhawks with linear dc voltage regulators. (LDO)

Tested on two very different multi rotors.

a) small 500 mm (19.5 inches) quad.

b) medium 1 meter (39.37 inches) hex

They both have frame that don't flex and CF propellers so no fluttering or other kind of prop vibration. 

Used the level acc calibration prior flying.Then flew very short time to have a precise view in the log file of the

CTUN (THR_OUT) value that I copied in THR_MID. (I still don't know why this isn't an automatic feature).

Anyway on both these aircraft I tried to:

- take off stabilize

- take off in alt hold fly and land

- take off in Loiter fly and land

Never been so "locked in" even some wind was pushing the aircraft down. 

A Heaven for camera handling. Was wondering why I used a 3 axis gimbal with vibration dampening! :-)

As this is before auto tune, I really wonder if I should go through the auto tune ?

Will try longer flights, missions and spline way points tomorrow.

If all goes well, I'll try RC-10 on a medium size (1.2 meter) quad X8 configuration.

Just a note: Prior take off, in Loiter mode, I checked on the telemetry laptop (rfdesign.com.au RFD900+ radio modems) HDOP and numsat which were very good (see log screen below).

@Shaun Bell: +1 (For size and weight) So at least we are two LOL LOL LOL

My tiny "beating" Quad is 500mm and used exclusively to test new RC-x version.

When things looks "~ok" then I try on real heavy lifters!

So don't feel "alone" ! LOL :-) and your findings often match mine. :-)

Kind regards


Just curious: Where do they place the Pixhawk? :-)

Went out to test rc10 this morning on my PH deadcat running Tiger MT4006s 10 inch props on 4s.  Took right off in althold and stabilize so I decided to run the autotune set at .07 -AGGR.

It took about 13 minutes to tune the three axis.  The motions were much less pronounced than autotuning in 3.2; pitch and roll seemed to be about 15 degrees as apposed to the 30 degree plus when ATing in 3.2.  Decided to land and disarm due to low battery warning.

Swapped batteries, installed Gopro and armed.  On throttle up immediately one motor failed to spool up to full speed, I dropped throttle, but it was too late.  The Vbrain 25a 4-in-1 esc burst into flame.  Fire went out in about 5 seconds with no other damage to the CF framed quad.

Wasn't sure how to set logging but it appears that MP 1.3.31 doesn't like the files.  It will not auto analysis the logs.  Message" Could not add reference to assembly mtrand.dll" followed by "Bad input file".

Am I just snake bit again or is there something in autotuning rc-10 that could have stressed one motor in 15 minutes?

Logs included:

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