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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You DEFINITELY need SOME dampening regardless of what frame you use. I "used" to use a dampening plate that I made out of the top camera mount on my 250 frames but now I use This with double sided carpet tape and it works VERY well. Much better than I expected to be honest.

This is my first post on diydrones, so hello everybody! Unfortunately I have to start with a crash. To cut the story short because I think I may have encounter a serious issue with AC3.3. Uploaded the firmware about a week ago, mainly because of the LG an Storm32 support. Flew without any issue, only once I think when I RTL in the descending phase over home is started wobbling kind of serious, I had to put it in stab and descend manually and it settled. All other autolandings were fine. Now the main issue, took off yesterday for the second time (on the side note, I was conducting a search over the sugar cane filed in search for a lost arduplane, flew LOS at low alt over the field and got caught in a downdraft, plus it was getting pretty dark) after a steady 6-7s climb (see log) the copter destabilized and crashed pretty badly right on the schnoz, (good thing it was wearing the newly handcrafted, perfectly balanced ST32 gimbal as a helmet). Looking at the logs I was puzzled to see that ch3 out went completely idle right before the crash for no apparent reason, the mag acc an gyro were stable, and the time frame tells me that the ch3 went dead prior to any change in the imu.I hope you guys can clarify this, maybe I am missing something. Just to add, my builds are very sane and thoroughly checked to the last detail, I'm a bit of a freak in this field so a mechanical problem is most likely out of question. I'll upload the video shortly, my internet conn is knd of sluggish.


It looks like a mechanical failure of the back right motor or ESC (#4) because the actual lean angle suddenly diverges from the desired and it rolls back and right.  The motor output backs this up because motor #4 suddenly goes to full while it's opposite (#3) goes to it's minimum.

Just for reference, the motor numbers can be seen on the wiki here.

I hope you're right, but I'm still not convinced what's the cause and the effect, from what I see the commanded motor reaction caused the roll, not the other way around. Some random acceleration/deceleration of the the motors is unlikely (checked all the motors/escs afterwards and they seem fine and within parameters), all my wiring is soldered, the single connector being FC-ESC and the pins are soldered also, not just crimped. And besides there's an inconsistency in ch4 out trying to stabilize while the ch3 stays low to the end with just couple of spikes. Obviously I know the motor numbers, the copter flew fine a dozen times with 3.3 and I am AC user since versions 2.xx and believed or not never had a crash, of course there's a beginning for everything, I am not frustrated about the crash though, I'm just trying to understand the cause. I'm also aware that I'm only human and did, can and will fail at some point with whatever I do, just want to find out if I just did or it was a divine firmware/hardware intervention.

And the video is ready (edit) at the end you can hear the lipo burst into flames. https://youtu.be/eAAU4joQtRg


You don't say when or where - on USB power or battery power? In your office or in the field?

Most likely a hardware problem with your pixfalcon. Even though you are using the external the internal is still checked for consistency. What offsets does the internal give you? Does the output in the MP calibration screen look truly spherical?

It also could be a problem with compass MOT - are you using this?

The orange foam is too thick for my QAV250. I use the neoprene foam that comes with the kit and that seems to work pretty well - on the mini quads the vibration frequenceis are much higher and seem to affect things less, so I don't think you need as much dampening as on the bigger quads.

I'm certain Randy is right - 3 and 4 move in opposite directions at the same time and 4 is then dead. No way the FC can keep it level with only 3 motors...

What motors/ESCs? Could be loss of sync with the ESC if its a larger motor.

Without any dampening on my 250's [I've built at least 1/2 a dozen now with 4 of them using APM Mini's] if I didn't use any [as in planting the APM down on the frame] I would get horrible ALT-Hold and Loiter modes not to mention such bad oscillations that it they literally flip on take off. One could say that it is less "important" on small frames more so because of the way they are flown [as in acro mainly] but my findings have been pretty consistent in the need of "some" dampening even on small frames. I'm betting when I swap out the APM Mini I have on my newest build with a Pixhawk Lite that it will also show the need for "some" dampening now that the EKF and Vibs graphs are available in flight. Since I am waiting on my Tarot T960 frame to come in and a rebuild of a buds 450 class quad I may take the time to swap out the APM for the Lite [god oh god the wires on both SO SUCK] to see. I guess I can mount direct to frame and test and also mount via the foam to test [I have both the white foam and orange foam] 

Man so many projects so little time sigh. Good thing I love it lol!

Hi Eduard,

I can confirm what Randy said. This is definatly failure of the back right motor or ESC (#4). It may have been a low battery cut out but I think it is more likely an ESC or motor failure. One one of my personal quads I had a broken solder joint that caused intermittent crashes but on the ground everything worked. I would try giving a very solid pull on each of your solder joints on that motor/esc. The thing that tends to show up damaged windings on a motor is full throttle while the copter is held down or mismatched motor outputs in flight. There doesn't appear to be any sign of the problem leading up to the crash so I suspect that you will find this problem is something that is a good/bad situation with nothing inbetween.

So first port of call is solder joints and low voltage cut off.

Sorry to hear about your crash!!

Almost certainly!

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