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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+1 For that!

It's tentatively on the to-do list for Copter-3.4 but I can't promise it because things sometimes get bumped.  I know Leonard Hall wants it as well so that increases the chance that it'll happen.

If that happens, please enable pixhawk to be an ESC configurator hub similarly to how it's done in clean/betaflight. This way people can bury the xRacer board inside the 250 frame for better ptotection. 

This would likely be a new request, so you'll want to submit that as a request on the GitHub repo.

This procedure was recommended a few times. The autotune takes the currrent parameters as the starting point, thus , doing it two times would make the parameters more refined.

If they are OK, with no wobbles, enjoy it!

I have two Pixhawk running arducopter with version 3.3.1 and one with
3.4-dev. The two have a message via NSH Overtime task 19. Is there a problem in flying that way.

yes please, oneshot support and blheli 1wire update through copter software

So I can use a pixhawk for 250 racers which needs fast updates to esc and processor of pixhawk is fast enough and software is excellent

RTH functions on a racer with all the close proximity interference of all the electronics ..... :(

Could case a lot of complaints about the excellent software which is designed for stability and not for racers, compass mot V3 for mini racers???

I for see a lot of questions


I used version 3.3.1 with coaxial octorotor. I try take off in Stabilize mode. Compass and GPS disable, because next step I want use PX4FLOW. But when I move throttle stick only on one step coaxial octorotor take off very fast and I cann't control it, when I move stick back on one step throttle too small for take off.
When I use 3.3.1 with quadrortor everything all right with take off.

Can somebody analyze my log? I will attach the file coaxial octorotor. thanks!


test flight a while ago, hovered it  3 meters away from me. My quad went to failsafe due to low battery. but instead of landing, it performed RTL instead of LAND. I thought it should choose whether to LAND or RTL based on hardcoded 5m rule? is this normal? Luckily i was able to switch flight modes to cancel RTL else it should have hit the wall.

I got this result after autotune on a X8, flys OK but values out of range or?

After installing 3.3.1, I noticed a couple of PID values changed: RATE_RLL_IMAX & RATE_PIT_IMAX to 2000 from the earlier 1000 setting.  Did the PID loops change such that what was 1000 on 3.2.1 needs to be 2000 to behave the same on 3.3.1?

I had a hard landing yesterday after trying LAND mode for first time since AC3.3.1 , it went to land but it never slowed down the descent speed before touching down, literally slammed into the ground....I have my land speed set to 45cm/s.....

log attached, anyone that can help out? I have been able to replicate the issue and even sent land speed to 30cm/s and it doesnt seem to make any difference

2 log files attached...i think on the second one i aborted the landing by switching to stab


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