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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Thank you for your reply.

Would you auto tune a multi that is yawing out of control?

When I loaded 3.3 this time I loaded rover first to clear all settings so the 3.3 install would be clean. Default setting.

This weekend I spent several hours balancing props to a gnat's hair starting with a new set. I remounted the FC using small squares of Kyosho dampening gel- the green 3/16 thick type.

Vibration levels dropped from +-3 to +-1. If I still have a vibration issue it would have to be a failing component, motor/ esc/ FC.

I have an extra Hawk FC so I am going to try that first.

Finally today I was in outside flying just for fun and not for work.

I had 3 fly-away in a row. During Auto-Tune mode.
AC3.3 rc8.
I had recovered my copter by switching in stabilize mode, and after switch I landed.

I ca not undestand why the fly-away start.

At the first tought I thinked that could be the multistar battery.
Since I'm using 10C batteries.

Now I'am not so sure that is battery fault.
Now I think that this is the problem:
It seems that when it switch to AUTOLAND mode due to battery failsafe, it start to flyaway. But why?

Of course that's what I think now.
I'am not sure.

Attached 2 logs that show two of the three fly-away.



Thanks for testing!

So what happened is the battery failsafe triggered a GPS-controlled-LAND but it was able to to control it's velocity probably because of a bad heading.  It looks like compassmot has been run on the vehicle but it's throttle based instead of current based.  The throttle-based compassmot is not very reliable because the interference is really related to current and throttle's relationship to current is not linear.  I've actually been considering removing the throttle-based compassmot.

The MAG messages are not present in the log which means I cannot directly check the interference level.  If you could set the LOG_BITMASK to "NearlyAll" that would be good for future analysis.

By the way, as a minor point, I wouldn't personally call this a "flyaway".  I think a "flyaway" is when the vehicle flies off out-of-control and out of the pilot's view.  In this case the vehicle was indeed out of control for a short-time but through some good piloting skills you re-took control before it got even 10m away.

Thank you for reply Randy.

You are always super fast (=

Yes, I have done a compass mot based on throttle.
Now I calibrate the Power Module for read the right current and I will do the compass mot current based.

And also in the next flight I will use "NearlyAll" on the LOG_BITMASK.

If I encounter any new issue I report it here.

Sorry for troubling.

Last thing is my opinion about the compass mot and this issues:
Yes, if a compass mot based on throttle could lead to this problem, I think that the user should at least be warned on Mission Planner.
I did not know that, and before you told me I was beliving that was super safe also based on throttle.

But this is only my opinion =P

Thank you again!  (=

Altitude Jump during AUTO mission.

On RC8, fully tuned including Yaw without any alteration afterwards (perfect feel, no twitching in Pitch), the drone is pretty stable and has had a number of flights in the Netherlands, without the strange jumpyness in Loiter,  I experienced recently at my holiday location in France...

After taking off in Loiter with a fast flashing green indicator, and a HDOP lower as 0.90, I took this heavy drone to approx 10m, when I noticed already a not so steady Loiter as usual (motor sound not monotone, but quickly ramping up, down, while maintaining altitude... 

Never heard that before in loiter....(as If GPS height position was not constant, and EKF was not smoothing it out)

Then switching to Auto mode for a 900m traject, at 20m Altitude, so drone started gaining altitude to get to 20 meters at first waypoint...and everything was still fine...

Then around the second waypoint it just shoots up into the sky full throttle, climbing quickly to approx 40m, after which it stabilized by itself, but didn't get lower to the original programmed 20m for the trip, so switched out of the Auto mode and brought it back in Loiter, where it remained very rough on the engines... i.e. sounding like ramping up and down rather quickly every now and then (as if it was planning to Shoot up again..)

So after it getting on the ground, it flipped (no harm done), I investigated the log, looking for the obvious like GPS Glitch or Baro problems, either one failing or whatever, but none of the above... (No EKF failures, and before shooting up limited VIBE in X, Y, and Z axis..)

Log at: https://drive.google.com/file/d/0BwKkz56PHqS0RE02VnJXaWc2RW8/view?u...

I am completely stunned as what happend here.., ???

Looks like high vibration levels.  Hopefully we will have some real-time display of this in the ground stations in the near future.  For now it's only visible in the dataflash logs but they are very clearly too high.

There is a marked increase in vibrations at the time this happened (particuarly on the Z axis) so I wonder whether something mechanical was at the root (apart from the overall bad vibrations that Randy mentioned).

You also have a Gyro dropout in IMU2 earlier on, I've not seen this before.

Thanks Randy,
I am however wondering why as the same platform has been flying fine for quite some time, i.e from 3.21 onwards....
At the first part of the flight when I still was in loiter the vibes are fine, it's as soon as it is gaing height in Auto it starts, but isn't this obvious as you are moving up fast ?
I.e are we looking at the result of the movement here ?
Thanks Andy, So maybe the dropout on the Gyro was the initiator of the jump in altitude possibly ?


The vibration levels are really quite high even at the beginning.  The AC3.2.1 vs AC3.3 resistance to vibration is a good question - so the biggest difference from AC321 vs AC33 is we've replaced the 2nd-order-complementary-filter (aka InertialNav) with the EKF.  We were expecting that that would improve resistance to vibration but in fact, it may not.  It may even be worse which would be a bit of a sad result.  PaulR (creator of the EKF) has started on the "New Maths" which is a large-ish change to improve EKF's robustness (i.e. bad vibes, bad sensor data) but that won't come until AC34.

AC33-rc9 will have one final change directly related to the EKF's vibration resistance, it's going to do a better job of picking the IMU with lower noise.  Hopefully that will help.

If you look at EKF4->SV you will see it jump above 2 which means that the vertical inconsistency got so bad that it stopped using the GPS. However EKF4->SH (the baro vert inconsistency) shows the same thing, so it seems more likely that the vibrations caused the inconsistency. Note too that the IMU clipping goes up at the same time, so I think probably you have some kind of cascading effect.

Ok thanks, I'll have a look if I can find anything moving around in wires under the PixHawk, maybe something started to move due to wind or so...
according to what I have read in the EKF settings, you may increase the importance of the GPS over the Baro alt correct ?

Could that be preventing it, if nothing obvious can be found in the hardware section... I do use vibration damping which is more solid than the original 3D damping, so I may need to go back to this softer stuff...

Currently the PixHawk is close to hard bolted to the frame..
Thanks again !

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