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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Did you do an auto tune with rc9?  What improvements did you notice? I still have 3.2 and it's a little squirrelly in the wind. 

sorry, my pids are really fine... I dont need autotune.

I'm getting the same thing on 2 different hawk lites, both only using the onboard compass.

Sorry I wasn't clear... What improvements over 3.2 I meant


Thanks for the testing, report and logs.

The usb-connected is only visible in the 9th bit of the DU32 message in the dataflash.  From checking the logs it looks to me like that bit is unset (meaning usb is not connected) so it seems to be working.  Also the battery failsafe triggering in these logs shows that it's ok.

The issue with the vehicle switching to LAND instead of RTL is because the vehicle was within WPNAV_RADIUS of home.  That parameter was set to a very large 30m (i.e 3000).  It's not intuitive that these two are linked so I think I'll hard-code the RTL vs LAND distance check to perhaps 2m or 3m.


There shouldn't be any changes to the control logic used for the sonar.  There's a change in the the Lidar-Lite-V2 is now supported but that shouldn't have had any effect.  If you can provide a dataflash log we can have a look.  Txs for testing!

Now there's a driver for the Lidar Lite V2, do we wire it up with I2C or still PWM?  If I2C, will it require any filtering?  Got a new blue labeled LLv2 sitting here ready to test : )

Hi Richard,

No problem.

Looks like really good improvements related with “vibrations issues”…

I have a frame only for test new releases, “designed” with high level of vibrations, and with this new release this quad is fraying really good in stabilize, althold, poshold and RTL.

A short video with the small quad (test frame) with pixhawk and rc9, and other with my Navio+ and rc9 with my high-end frame.

Really nice with wind ….my pids are tuned to be a little aggressive a hate fly like a “bus”

A short video…



So it looks like super simple mode is setup for the 2nd flight mode (AltHold).  Because AutoTune was triggered from ch8 (an auxiliary switch), it continued to use super-simple when the vehicle was in AutoTune.  Super simple has a 10m dead-zone around the pilot so when the vehicle crosses out of this deadzone the controls end up suddenly being rotated.  Basically for super simple it's best to keep the vehicle outside the 10m deadzone to avoid confusion.

The final fall looks like a mechanical issue.  In particular it rolls left and back so probably motor #2.  Motor #2's output goes to full which is also consistent with this theory.


I think sticking with the PWM input is probably best.  Tridge has found on his sensor that it temporarily started reporting an altitude that was 13m off from reality when using I2C.  That's just one sensor though so we don't really have enough data yet to know whether the I2C connection is good or not.


which brings us to the need of having Simple and Super Simple being reported to the GCS's :)

Thanks Roberts looks good!

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