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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Well, that was pretty accurate analyzis. Got the problem again, but this time better pids and no gimbal, I was able to control the thing and saw clearly that motor 5 was the problem, it almost stopped. Any idea what could cause motor malfunction? Magnets? bearing? esc? Motor or esc are not hot, maybe little warm only. Bearings doesn't seem that bad at least compared to others. These things seems quite hard to "debug"..

Again, after that I was able to fly normally and did autotune. Tried to land in althold, landing was not recognized correctly and copter flipped.. Did read later posts about the same behavior. Hopefully landing will be tuned better in future.

A few points.

Can't provide bin files and can't figure out why, but that's another issue.

This TLOG has some of the tests I managed to do after lunch, and there's something weird with FS_THR_VALUE that I had set for 960 and only after disabling the Radio Failsafe I was able to fly. Radio Calibration done.

Radio system is DSMX and is set to bring CH3 to 930 with radio off and I can see it on the Failsafes screen.


First impressions without auto tuning is a flawless flight but with the windy conditions I had AltHold was behaving reasonably well, PosHold was unable to get a fixed position, and Rob's Break mode was absolutely fantastic, because it kept the small quad absolutely static on the spot.

Won't test more, until I can figure out what's wrong with the damn FS_THR_VALUE, because I don't want to fly very far without Radio Failsafe.

ps: As a side note. I hope Paul is able to offer us all some aluminum made cars, because at 2m distance from my car (Honda) Compass Variance of the EKF goes nuts......

now to see why I don't have logs on the damn microsd, and no warnings from the card....

  This "flip on landing due to a small lateral move" problem really looks a lot like an unbounded integral wind-up issue.  Preventing the error from accumulating to an unreasonable degree should do much to control this.

  Limiting a max tilt angle is also something that should be prioritized over position corrections in a landing type of flight mode mode.  I suspect that without first better limiting integral wind-up,  limiting max tilt angle won't actually be effective.

  It would seem that the ideal behavior would be as follows:  In a situation where a copter meets resistance while moving laterally, it should tilt in a controlled manner to a maximum angle and then hold that angle indefinitely.

  This may fall under the category of "easier said than done", but it seems like a reasonable goal.   Very likely the changes needed to effect this behavior would result in undesired effects in some flight modes, as such it might make sense for the changes to only be effective in landing types of flight modes modes.


something else Randy.

Bunny hopping on land still here :)

It should also be noted that a number of flight controllers actually "turn off" the integral portion of the PID during take off to prevent flipping in situations where the operator increases the throttle slowly.


I had to stop mine with a stick the other day. I was practicing flying close to trees at the edge of a little glen, when I hit some leaves and then landed in a patch of weeds. To my amazement, I did not crash!

However, the motors just kept going at just high enough speed that only some entangled foliage was holding the quadcopter down, and nothing I could do with my radio was changing that. (This is on 3.2, btw, not 3.3).

I looked around for a stick and used that to push the safety switch, which turned off the motors. Why do I occasionally get these issues with shutting off the motors from the radio?

Does anyone knows if the receiver failsafe option will be back on AC 3.3 version?

Hi all,

Trying to load Rc11 (and RC10 for that matter) with APM Planner onto my pixhawk (non 3DR version) I haven't had any issues loading firmware in the past but now I can't get past the status showing "Requesting CoA" ...It won't load stable also. I tried QGroundControl and I was able to load firmware on using that. Unfortunately I had to download the source then do a custom load. I have Has anyone had any issues with this? Tips/advice?



GPS is certainly important to consider for trying to land in Loiter/Pos Hold, but I believe the issue is quite evident for Alt Hold as well.

if you do have LIDAR/range finder, is it taken into account in the landing logic? I haven't reviewed the code so I can't say personally. If you are saying it should be a requirement for larger craft, I am assuming you use it and have found it to be taken into account, correct?

did you try jumping to Stabilize? If you had, and you had the throttle stick at minimum, the motors definitely should not be spinning. 

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