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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yes I have M8N and 6M, and the M8N is always lower HDOP , but i have had then switch in flight with no issue, seems to work ok for me in that regard and i have tested it too (by disconnecting the TX wire from GPS into Pix via a relay switch)....but i dont think the issue am having here is related to having 2 GPS necessarily...

Did you look at the EKF while it was in the air?  At first glance the vibration levels don't look bad despite the clipping, so maybe the following is a waste of time, but is my experience with knocking vibration down. However, I would think with your setup hard movements could cause wobbling and weird IMU behavior. OTOH I could be totally wrong.  

On a quad with not a lot of real estate to mount stuff, I ended up doing this, which resulted in very low VIBE levels. It has a AUAV-X2 secured with 3m tape, but has had a Pixhawk. Another thing is 4 10-12mm squares at the outer corners seem to isolate vibrate best. HK Orange Latex is very good and you get a lot for <$2. I think it may even work better than the 3DR foam which isn't available now. Rubberized cement holds well.

I also found that mounting plates that look like swiss cheese do not bode well. On this copter was glued a thin piece of aluminum plate to give a solid surface on a pretty flimsy CF plate with lots of holes. Without that vibrations were marginal. With it, nearly nothing. Rarely do I mount directly to the top plate unless it is solid. The Pixhack is a nice product btw.

On this one with a Pixhawk I used 4 Plexiglas pieces mounted on the top plate using 3M 10lb tape. It's thick and helped isolate vibration. This picture was taken when it had 3DR foam, but now has the HK latex.


I'm still learning how to interpret 3.3 data, but:

Vibration is very bad.

Is there a power module connected?

Battery levels aren't logged

Current not logged.

Mag levels out of the ballpark.

No Mag offsets.

EKF must have been doing somersaults.

What radio are you using with the KDE ESC's?  I could not get them to work on my latest build; very odd behavior on arming.

How did you set up the end points? I am 100% sure it was set up properly on mine. On arming, one motor would not spin, even through the entire throttle range. Other times it would spin and once in the air seemed ok. However, I could never get a consistent arm/spin out of them.

Dear Randy

Please help me
I have change new pixhawk to my iris+ and setup fw 3.3.1 and calibration all. What is happening now is that Altitude Hold and Loiter are unable to maintain a consistent altitude. When I keep the iris+ hovering in place (either by manually doing so or using loiter), I get an altitude change of +/-1-2 Meters or more 10-20meter. This is a bit of an issue but even more so is that when I fly it laterally, it loses altitude quickly when i switch loiter to alt hold and all of a sudden pitches/rolls violently then shoots up into the sky where I have to quickly change over loiter and back to land.

thanks you so much !

here is logs file.


Hello every one,

after autotune with aggressive 0,05 i had the following values. only stab p for roll and pitch was too low. i raised it. the copter flies well, in windy days too. but there´s a big problem with my ccd cam. it wobbles strongly and it´s no rolling shutter. my question is, if it is a mechanical problem with cam or a pid problem.

and the problem is taken the most affect only at flying against the wind. my vibrations aren´t bad.if i compare pitch or roll with yaw i see at pitch and roll many peaks.yaw is very clean and i love it. could the peaks be the reason of my problem?

the frame is a h4680 with 4s, tiger mt2216 900kv and graupner eprops 11x5.

attached are a picture of pids, a picture of pitch and a log.

i hope, someone can help me.



Since 3.3.1, it seems there is a regression with NMEA GPS support compared to 3.2.1. For example, these are NMEA messages refreshed at 4hz:


With 3.2.1, Mission Planner shows "3D Fix". However, with 3.3.1, Mission Planner shows "No GPS" or "No Fix" most of the time. Mission Planner shows sometime very briefly "3D Fix", but it turns to "No GPS" or "No Fix" immediately.  

When I checked the code at https://github.com/diydrones/ardupilot/blob/Copter-3.3/libraries/AP... I do not see anything unusual.

Any idea?

is this with a m8n module? And why are you using NMEA?

It is not m8n. I use a Novatel module that outputs either NMEA or Novatel native messages.

When you upgraded did you happen to go to full or tree then GPS1 and set it to NMEA?

Yes, tried to set the GPS type to NMEA. But this does not help.

what happens if you flash it back to 3.2.1?

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