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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I think the dropped messages are more likely:

1. a serial bandwidth when the number of satellites is very high

2. GPS internal speed limitation that means it can't keep up with all that it has to.

3. a logging problem - we log a lot of data in AC3.3 so the SD card may not be able to keep up.

There's an issue on the issues list here about the M8 and configuring it to reduce glitches.

Reducing the update rate of the GPS to 2hz is not a good idea.  The EKF wants it at 5hz.

The thing about the Vibe message is that you aren't looking at the "spiky-ness" of lines, but merely the maximum height. In your case, about 8 max on the green line, is quite good.

It's a guess but I'd expect the two radios to have different settings for the RTS CTS checkbox.  Above is a screen shot of one of my 3DR radios and I'm surprised to find that it's unchecked.

@Brad, I'll review that PR (or maybe Tridge will).  As you guessed, it's just a matter of time and I've been concentrating on trying to get the EKF and it's vibration resistance sorted out with Paul.

Randy, did you have a chance to look at those 3 logs I posted? They have no GMS value issues.

Not to mention you're running a REALLY old SiK version. 1.9 is the latest from Tridge.

Hi Guys! I am making a crosspost to gather as much information as possible. I do not have a teensy yet but according to the APM Copter wiki it is not necessary anymore if I´m using a Pixhawk and Copter 3.3 RC8. I would only need the FrSky FUL1 and a diode.
I was wondering if this is true and if I can use lua scripts found on the web in that case.
Thanks a lot


Tridge, Michael DuBreuil and I had a look at the 3.bin and 7.bin logs and all show missing GPS messages.  So we think the cause of the missing messages is just that the SD card in that Pixhawk can't keep up with the 400hz IMU logging.  about 20%~30% of all messages are missing.

Maybe you could reduce the IMU logging down to 50hz and do another flight so we can confirm the GPS rate is coming out reliably at 5hz?

The HDOP coming out as zero is a bit annoying, it means the config messages at startup are not getting through to the GPS.  We likely won't be able to fix this for AC3.3 unless a lot of people start suffering from this problem.  An alternative is to get the default config for the GPS fixed.

I guess you're using one M8 and another lower version Ublox (i.e. Ver6 or Ver7)?  The logic for deciding which GPS to use is based on the number of sats (not the hdop) so if you're using an M8 which naturally has a higher used sat count, it's almost guaranteed to use the M8 over the 6 or 7.

ok, thanks for the response. not sure if you looked at file 4 I posted there - that one had 0 hdop...

both GPS units are same m8n, but a different kind of chips is used, so one with hdop 0 usually has less satellites.

again, an issue that I have had repeatedly was related to very erratic behavior of the drone when HDOP=0 is showing.

What exact mask I need to use for logging to switch for 50hz?

Thank you both for the reply's.

      I'm going to forge ahead and keep messing with the ATC_ACCEL and Throttle acceleration controller P gain Parameters to minimize the Z movements further. Tuning for >10X optical zoom lenses are a pain. 

Paul, for logging set the LOG_BITMASK so that IMU is checked but FAST_IMU and RAW_IMU are not.

Can you explain please? As I can see via IMU/IMU2 vibration is acceptable. 


you should look at the Vibes messages (see: http://copter.ardupilot.com/wiki/common-measuring-vibration/ for more details).

As Rob mentioned the vibes are "extremely, extremely high" on your copter - they go up to 120. Normally it should be below 30. Below 50 should be ok. Depending on the damping system, the balancing of the props, and the frame setup it is possible to get the values below 10 even for larger copters (for in Loiter the vibes on one of my copters are < 5). 

I suggest to change the damping system and to carefully balance the props/motors.

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