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 am using HobbyWing XRotor on one Y6 with KDE 515 motors, and HobbyWing Quattro 25A 4-in-1 ESC on a quad with the same KDE motors. Both work very well with Pixhawk and remain cool, even the Y6 with them installed in the arms. HW is the ESC of choice for me now.

Y6 AUW: 3.2kg

Quad AUW: 2.7kg

That after trying Maytech ST and ZTW Spyders unsuccessfully. The ZTW is now on a quad that seems to work ok, but on the Y6 I couldn't get 6 motors to spin to save my life. It was a real stumper why they wouldn't work. If it was an issue with Pixhawk, the reason was never discovered. 

I'm now building an X8 which will likely use the same KDE 515 motors and two HW Quattro ESC's. On 4s these motors are flat out beasts; haven't found another that can compare yet. HLY, SunnySky (not saying they aren't good motors) and several others just don't have the horsepower and get too hot on 4s when AUW exceeds 2.5kg or so with say <600kv.

The only issue remaining is getting the tuning perfected. It's close, but not quite there; after 1 1/2 years using AC I still haven't tried to learn how to play with PID's very well, and now there are several other variables. "Auto" is such a nice sounding word.

Off my soapbox now.

On my 800 class X8 I use RCTimer 30A opto escs and they works awesome.


Although my motors are only 750kv I don't get any heat or sync issues what so ever and loaded, with gimbal and batteries weighs in about 3.6kg, I also use 4S and really can't find fault with these ESCS and they are cheap to boot :)

I personally would not think of using 25A escs myself let alone quatros as I would hate to have "1" go out and loose the ability to use the other 3 :( Just my opinion.

They act like 4 separate ESC's, 25A each.  If one fails, the other 3 still work. The wiring is so simple and clean. Two power wires. For X8, stack them.

Per eCalc (which I don't fully trust) the X8 will pull ~5A per motor @hover, 20A full throttle. Why on earth would I use 40A ESC's.

I really push the quad hard (aka Dixie Cup) with the Quattro. 

BTW, Steadidrone uses Quattro's on their setups.

No room inside the frame, so it fits neatly underneath. No spaghetti mess.

Expecting moderator to step in at any time :)


We won't fix the dual GPS issue in AC3.3 I'm afraid.  That will be an AC3.4 improvement.  I'm going to change the wiki to say that we don't recommend a dual GPS solution for copters until this enhancement is in.


I'm really not aware of any changes that would cause that kind of behaviour.  As far as I know when the throttle stick is moved just above the top of the deadzone (for example) it will command a very small climb rate, not 20%  We can look into this but the log would be good to see first when you get a chance to upload.

I use the same thing with no problem. I can't believe they haven't been more popular. Way less RF noise, cheaper, and and much better wire footprint. I have yet to see any downside. It all adds up to a very clean build. 


Great.  No need to do AutoTune I think at least in order to resolve this problem.

Thanks for providing the link to the vibration mount.  We can't be completely sure because each copter is different but from the vibration data it looks like this solution is not as good as the 3M foam or hobbyking orange foam mentioned on the vibration wiki page.


Sorry but did you post dataflash logs anywhere?  Ideally with the logging-while-disarmed bit turned on.  It's likely that the EKF is unhappy with the velocities coming from the GPS but we will need logs to be sure.  The "Bad AHRS" message sounds like something else is going wrong (like an IMU).

I was able to load up the above file into the latest beta version of the Mission Planner.  I haven't analysed it much 'cuz it looks like it's a forgone conclusion that it's an ESC issue... still, I just wanted to mention that MP can open the file.  By the way, normally we like the .bin files because they're a little smaller.

A correction to the 3rd point.  I checked with our GPS maintainer, Michael DuBreuil, and as Josh Welsh says, the baud rate is being set back to 38400 so it won't help to change that with u-center.  Sorry!

Michael also suggested that Paul Atkin may want to disable SBAS (i.e. set GPS_GNSS_MODE to "1") because based on you location you could be picking up a WAAS satellite from very far away.


Thanks for testing.

That's normal if you're arming in Acro, Stabilize or AltHold mode.  If you managed to arm in Loiter, Drift, PosHold or Guided without a GPS lock then I definitely want to see a dataflash log!

DG any chance you flashed those with BLheli? 

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