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 had a similar thing happen on one of the earlier 3.3 versions.

Started spinning and would not respond to yaw after a hard maneuver.

The problem was two fold, high vibration levels and the motors not level enough.
This was on a folding quad, the booms pivots were wearing out allowing about 2-5 degrees of twist. Fixed the booms and found the vibration issue, flat spin problem solved.

switching into Stab mode would've given you full manual control stopping any autopilot initiated maneuvers. Also, since throttle in stab is manual copter is far less affected by vibration and absolutely not affected by bad compass, glitching gps or sudden pressure changes. 

I too learned about stab mode the hard way :) 

not completely sure, but it looks looks like both compasses went crazy due to a current spike. 

those large setups do need compasmot. 



Sure, enhancement requests/suggestions should go into the issues list.

Thanks for looking over the log. I saw the the mag reading and suspected the same thing. I got a little anxious to see if it would fly and did not take the time to do the compasmot. I did switch to stab with no regain of control but I was near panic mode thinking I was about to auger in another high dollar build. Put it down in the grass with one broken landing gear so I really got lucky. We have heavy rain predicted for the next three days so I'll have plenty of time to complete the setup. Thanks for the help

PaulR and I had a look at this and altough it could be the compasses we think it's more likely to be a mechanical failure of some sort that weakened the clockwise spinning motors (#1, 3, 6).  Our best guess is it's motor #6 (back left) because the vehicle rolled left and pitched back as well as spinning.

Supporting the mechanical theory is if you graph the Desired Yaw (red) vs Actual Yaw (green) you can see the that the Actual is leading the Desired (Note: this ability for the desired to drag around the actual is a safety feature so that if/when a vehicle recovers from a spin it doesn't then try to whip around to it's previous heading).  If it was sensor failure leading to a bad heading estimate then we'd expect the desired to lead the actual as the yaw controller tries to spin the vehicle (also EKF innovations would have spiked higher and faster).  In this case the controllers are not happy with the spin (see 2nd graph of Yaw Rate).

Also the bottom graph shows the motor output, they're all fine for a while but then suddenly diverge and it's the clockwise motors that go high and the counter clockwise hit their lower limits.

Thanks so much for taking the time to look into this. That makes sense because it could explain the current spike at the start of the event. These are fresh motors and ESCs so I will contact KDE and see if they can help with analysis. Are the mag fluctuations during the event due to the spin?

the copter responds to switching to stabilize in overriding the Landing sequence now if i use the flight mode switch on taranis. but when i use a toggle switch which i programmed to override the ch5 pwm, it does not work.. no switching from landing to stabilize. at least now i can confirm that the overriding still works 

Hi, where can I find the THR_MAX parameter? Because my Quad does not take off, only when i give over 80% throttle. The motors can lift up to 2,3kg per Motor and the Quad wheights circa 2.8kg.

hi Maciej,

      I did an autotune and it maybe similar with your test. After I did autotune, it was perfect, but when I went to fly another day with a full battery 6s, the voltage was about 25v (higher than the voltage during autotune), it was very unstable. So this problem maybe result from battery voltage. During autotune, batt voltage is lower, and PID value from autotune is suitable at that time, but when use a full batt, those PID values become unsuitabe, accurately, too large.

     How do think about that?



what is going on with 3.3.1 ?

I had for long time 3.1.5 my OEM Pixhawk was flying perfectly

then 2 weeks ago I upgraded to 3.3 . did full wizard from Mission planner. I found out that THROTTLE is not cutting directly to my input but it is delayed and somehow props are still spinning for 1 second when my throttle was down. Then I tried GPS mode and it was not keeping position at all , attitude mode was working ok, and stabilize mode ok.

then yesterday I updated to 3.3.1 and now I got BAD GYRO HEALTH on mission planner but artificial horizon looked ok, I tried the wizard again and it FAILED on accelerometer test . I ignored it then went outside  and right from the start CRASH like gyros would not work at all. so what is going on ? instead working better and more user friendly looks like programmers make our life worse. I think I will go back to 3.1.5 when all was predictable and working fine.

if anyone cares I can add my logs. I mostly fly on stabilize mode and atti. 

mu setup : 500mm quadcopter frame , with pixhawk and 3dr power meter and 3dr GPS.

If your accel failed, it's a bad omen for your next flight.  Lets see a log file.  I'm thinking it's going to be the controller, but can't say from just what you've told us.  I've had two Pixhawk's that I returned for this reason.  Though mine were different in the sense the horizon was all over the place.  

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