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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Hi Wilson,

just a short note for now:
your copter has pretty high vibes (up to 80+) and the accels are clipping - in both logs. So you should look into vibration damping. Unfortunately, the wiki page with some more details (http://copter.ardupilot.com/wiki/ac_measuringvibration/) is currently down.

Attached you find two screenshots based on the raw data.

Best regards,



This should be an interesting log for the devs because it seems on the edge where the EKF might run into problems.


My pixhawk accel calibrates fine on 3.2 but refuses on 3.3rc8.  Could this be linked to the acceleration sensitivity being increased?



Hello Folks,

since -rc8 was released I´m using it. I´m flying every Day min. 1h. No faults every thing worked very good.

Only on thing does not response is the "DO_CHANGE_SPEED" command. Just nothing happens! But I´ve to say that I´m using ch6 to change the WP_Speed. My thought is the the DO_CHANGE_SPEED command overrides the WP_Speed and if a new WP_SPEED comes from ch6 it overrides the previus command.

I would appreciate a "condition_change_speed" AND a "condition_change_VS" (VS=vertical_speed).

Yeah I autotuned roll and pitch axis with rc8 yesterday with aggressiveness set to 0.5.  Roll axis is OK but pitch axis took forever to autotune and now I get slow oscillation on the pitch axis when it recovers from significant pitch movements.  I'm going to re-autotune today with 0.7aggr and see what happens.

Hi all, quick question if I may.

Since upgrading to 3.3rc8 I'm having problems connecting via the radio telemetry port. I no longer get the flashing red LED on the air side half of the pair. I thought the receiver had failed and purchased another one. But this is the same.

I can roll the firmware back to v3.2.1 and everything works fine but as soon as I revert back to 3.3rc8 it refuses to work.

I read this thread daily and don't recall any notes about this so I thought I'd ask.

Any ideas?



Thanks Thorsten very much for looking into the my logs. ^^

Does clip0 mean too much front<->back vibration, clip1 mean left<->right vibration, and clip2 mean up<->down vibration?

And can I assume acceleration > 80G can only be done by hitting the pixhawk physically? (by hard-landing for example).

I am using the 3DR pixhawk with the 3DR vibration foam. I see my clip2 remains at 0 for the entire flight. Maybe the foam is helping here.

But I am running many wires (RC in, 4 motors, bluetooth telemetry, minimOSD, GPS, power-supply, I2C, buzzer, safety button). Some of the wires are not flex enough so maybe these wires are pulling the pixhawk front/back/left/right, causing the clip0/1 to increase steadily but not regularly.

Does this make any sense?

So the reason why IMU::AccX/Y/Z looks good but ACC1::AccX/Y/Z looks bad, is because IMU::AccX/Y/Z does not capture this "wire pulling" moments?


btw omg if the vibration is really due to the wires .... I have to redo most of my connection~!! 

Have tested from rc1 still have the very same experience that position hold is behaving strangely (1) unreasonable rapid roll movements (no wind) after switching from Loiter (2) very bad breaking performance even with max settings (angle/speed of change).

[cannot upload logs due to size]


I´ve the teensy working with -rc8

Hi Thorsten, 

I have checked the 1st flight log (with Raw-IMU off). The clip0 and clip1 are also climbing, and clip2 remains at 0. I think vibration should affect AccZ (clip2) more easily than the other two axes. But my situation is the opposite.

By plotting IMU:AccX/Y/Z and clip0/1/2 together, the AccX/Y seems to be within +3/-3 range. However the clip0/1 are still climbing. So my vibration is OK according to AC3.2.1 standard but seriously out-of-range according to AC3.3 standard? @@

I suspect the clipping is due to the hard-rolling/-pitching actions during autoTune. So I plot the clip0/1 with some ATDE logs. Arbitrarily I choose ATDE::angle.

Interestingly, the clipping is not due to autoTune. But in fact it seems to always happen when I interrupt the autoTune. My interruption introduces a batch of clip0/1 increments.

I didn't move my copter that hard (> 80G) during autoTune. Just some gentle pitch/roll to bring my copter back. Why the clip0/1 counts up that many? Or maybe my ATC_ACCEL_* is too high?

And what actually makes clip0/1/2 to increment by 1? 

Sorry for so many questions : p wish you would be interested in looking into my situation.



I see this when there are too many log files on the card (>50?). You might want to try removing some if this is your issue.

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