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 can't take credit for the idea, someone here led me to the same information, paying it forward as they say! If you can't feel any additional end play, then it probably isn't a major contributor. Still worth looking at, but not likely to help a lot unless you can feel some end play.

As far as what the clamp looks like, it's fairly simple and from what I've seen, usually home made. The basic construction is usually a section of square steel tubing large enough to encompass the motor. A hole is drilled and tapped in the top center and a bolt is threaded in that location such that when a motor is inserted the bolt can press on the shaft. Opposite the bolt a clearance hole is drilled for the end of the shaft on the other side. There is usually a grub screw on the bell that secures the bell to the shaft. Once this is loosened you can compress the shaft and the bell housing together.

I'm not sure where the original thread is but I'll look around and see if I can find it. I think it was Leonard who originally posted the fix in this thread.

Yes, Arms flexing could definitely cause Z axis vibrations.


Nathaniel ~KD2DEY

thanks for taking the time to type all of that :D - I will look into it. 

I'm seeing quite a bit of flexibility in the RCTimer F450/F550 extended length arms. so my first thought here is the arms are probably playing a roll in this Z vibration. they are durable as heck though, and cheap, so it makes for a good test platform. I think my next step will be to swap out for CF tubes and the F450 frame adapters / motor adapters. have to see what the weight differences are though since the adapters are aluminum.

thanks Paul-

Nice!!! Very Goool! ha

Great idea! I have often held the copter from below [ on first set up ] and in stab mode throttle up until it just about holds it's own weight. You can tell right away if one or more motors are not spinning right or being controlled correctly by moving the copter around a bit by hand... it should of course fight anything making it out of level. I also point each motor down and compare all of them for vibrations. Seems like it's not unusual to feel one motor and or prop still needs some work. You idea is probably a bit safer than what I have done!

if this feature is going to be in AC3.4 I definitely will install the 3.4-rc1 and test my copter immediately.

thanks for all the great work the AC3.3 is now more vibration resistance. If 3.4 has this feature than it is not only tolerate but even help reduce vibration.

one more +1

Hey, a bit off topic, but could not find another place where this might be noticed by correct people (do not know who exactly): 

Antenna tracking firmware for apm/pixhawk is lacking support of continuous rotation servos. I understand why there was no such support with the MP based tracker, but since we have IMU on the physical antenna, I think it should be farely easy to add support for continuous rotation pan servo. It is so easy to turn almost ANY servo into a continuous rotation one by immobilizing potentiometer in the middle position inside servo with some glue.

I always use my flight stand I made out of some old wood and PVC pipes. MUCH safer than holding on to it :)

Use a flight stand-  I would not ever suggest holding a quad in your hand with props on for testing, at almost face level no less... Esc's and FC's can glitch, a throttle control can get bumped. It does not take much of an accident for that quad to jump out of your hand and bite you, and those spinning blades have much more force behind them than you think.  I have two scars on my chest to back that up.

What happened? An esc glitched and one motor went to 100% throttle instantly. Your reflexes are not physically fast enough to react to something like that. be safe.

Sounds to me like another YES vote for a one-motor-at-a-time real time vibration motor test app...  :)

How did I know you'd be agreeable to this idea?  :)

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