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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Re-Welcome Thor, congrats for your Solo, perhaps you can find much more complete the instructions now if any one give you the answer http://copter.ardupilot.com/wiki/arducopter-parameters/   I'm only use the param that you mention, please share if you find what you say.

Hi Cala,

I looked at that list but i didnt see the Param but i will look again and check back again! thanks for responding to my comment.

TMT, I have my WP_YAW_BEHAVIOR set to '1'. 'Face next waypoint' and it comes in on RTH and rotates to launch heading for landing

Cheers. RB

Hey Randy thanks Alot!! i knew it was an easy setting!!! i just couldnt remember from APM 2.6 days how i set it!! i appreciate your response!

Hi Craig,

More tests shows that this regression appeared since this build :


This corresponds to the commit the same day:


I see there were 2 changes regarding to NMEA GPS.

Hope this helps,


was it with aggr=0,05?

i hope for better weather to test

These changes introduced a delay (negative or positive) between  _last_GPRMC_ms and state.last_gps_time_ms. This delay depends on the baud rate, and also probable depends on the order of the messages.

I had an unpleasant throttle cut when flicking from Stabilize to Loiter on the new 3.3.1 the other day, and I haven't been able to figure out what caused it yet.  I have just upgraded from 3.2 which has flown fine for a long time, but on my second or third flight, after landing to fix the camera and then taking off again, the moment I flicked into Loiter from Stabilize it dropped (3 metres) to the ground out the sky.  From the logs I see that just after mode change to Loiter at 10:53:40.932 Throttle was cut from 500 down to 129  over a couple of cycles without me moving the throttle stick from centre position.

It's a DJI S800 Evo running pixhawk, good conditions, no sun, no wind. It had been flying fine on Arcudopter 3.2 for several months until now.

It just suddenly happened on 3.3.1 on my second flight. (The first flight went ok, although the copter seemed very jumpy).  - GPS situation looks good,  Vibrations look ok. Is it an EKF problem?

I'm Reluctant to try it again so I might downgrade to 3.2 again for now...



That's occurs to me too and reports, Is something that change in params from 3.2.1, if you have the throttle higher, don't occurs, now I change dead zone to 80 and raise a little mid throttle and not notice anymore but I didn't have enougth time to try to reproduce better the moment when occurs, next fly I'm going to try it more times.


First off, I'm very sorry about your crash.  .. and unfortunately I believe you've uncovered a bug.  The issue appears to be that the desired climb rate is not being reset properly as the vehicle enters Loiter.  Instead of being reset to zero (or better yet the vehicle's current climb rate), it's being left as whatever it was the last time the vehicle was in Loiter.

Below is a graph of the issue recreated in the simulator.  Around the middle (see "6") the vehicle is in Loiter and the pilot's throttle is pulled low which demands a -ve climb rate (5m/s in this example).  The vehicle is next switched to Stabilize, throttle is raised to mid and then switched back to Loiter.  At this point you can see the climb rate (in green) dips as the desired climb rate starts again at -5m/s instead of zero.

So, very crappy, and sincere apologies.  I'll post a warning and we will fix the issue and push out Copter-3.3.2-rc1 for testing asap.  I imagine that will take a day or maybe two.  If we can get the -rc tested, we could have an officially fixed version within two weeks.

Thanks very much for the report though!

Thank's Randy, I wait too to test the rc1

Ah right, ok thanks Randy, that's restored my faith in myself and everything else!  At least it's explained.

Yes I had taken off, landed in Loiter, throttled down (still in Loiter), fixed camera, switched to Stabilize for takeoff again, took off in Stabilize,  and of course when I then switched to Loiter for the second time the above is what happened.  I think it throttled up again a bit just in time before the craft hit the ground, so no apparent damage done luckily.  The copter just fell over on it's side rather awkwardly, as I throttled up myself on the stick to save it.

Will await the update. Many thanks for the swift diagnosis.

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