ACRO bug (fixed in 2.9.1b): while doing flips in ACRO mode, if you switch to Stabilize while inverted your throttle will go to minimum.  To regain throttle control you need to switch back to ACRO then back to Stabilize again (i.e. switch to stabilize twice).  You never lose control of roll/pitch/yaw.

Loiter/AltHold/Auto/RTL bug: if you switch into these modes with throttle at zero motors will go to minimum until you raise the throttle.

Auto mode altitude bug (fixed in 2.9.1b): setting a waypoint altitude greater than 320m over home altitude may wrap around and instead be interpreted as a low altitude.

ArduCopter 2.9 is now in the mission planner and the downloads area!

The major improvement is we use inertial navigation to improve altitude hold.  This increased reliance on the accelerometers means you must do some additional set-up before flying:

1. Perform the new accelerometer calibration in the mission planner (video).  The auto-trim metho has also changed (video).

2. Add vibration dampening foam between your frame and the APM.  Some suggested materials: DuBrogelhk foam.

 3. If upgrading from 2.8.1, modify the throttle and altitude PID values:

  • Increase your Throttle Rate P, reduce I to zero, increase D
  • Increase Altitude Hold P, reduce I to zero
  • Tune Throttle Accel P and I terms but try to keep P about 1/2 the size of I


Here is the list of major changes (a more detailed list can be found in the release notes):  

  • Alt hold using inertial navigation (Leonard, Randy, Jonathan)
    • AUTO_VELZ_MIN, AUTO_VELZ_MAX parameters control the max climb/descent rate for the autopilot (cm/s)
    • PILOT_VELZ_MAX controls max climb/descent rate for the pilot (in cm/s)
  • Landing improvements (Leonard/Randy).  Copter will descend to 10m or until an object is sensed with the sonar.  Then slows to 50cm/s descent (speed can be adjusted with LAND_SPEED parameter). (video).
  • Surface tracking with sonar (Randy/Leonard).  Copter will attempt to maintain current distance from objects in front of sonar regardless of altitude.  Only used in alt-hold and loiter, not used for missions.  Sonar can be enabled/disabled with CH7 switch. (video)
  • Failsafe improvements (Randy/Craig/John Arne Birkeland) including bug fixes, additional check for PPM encoder failure and implementation of battery failsafe.  Set-up instructions are here.
  • Mediatek gps driver accuracy improvements and use of SBAS [Craig].  Instructions on upgrading your mediatek to firmware 1.9 are here.
  • Traditional Heli improvements (Rob) including (a) bringing heli code back into the fold, (b) enabled rate controller (previously only used angle controllers). (c) fix to rotor speed controllers - now operates by switching off channel 8.  (d) allow wider collective pitch range in acro and alt hold modes vs stabilize mode  (e) bug fix to allow collective pitch to use the entire range of servos
  • Acro trainer (Leonard). Copter will return to be generally upright if you release the sticks in acro mode.
    • ACRO_TRAINER : set to 1 to enable the auto-bring-upright feature
    • ACRO_BAL_ROLL, ACRO_BAL_PITCH : controls rate at which roll returns to level
  • Camera control improvements (Randy/Sandro Benigno):  (a) AP_Relay enabled for APM2  (b) Trigger camera with CH7 or DO_DIGICAM_CONTROL command  (c) Allow pilot override of yaw during missions and fixed CONDITIONAL_YAW command.
  • PPM sum support for transmitters with as few as 5 channels (Randy/Tridge/John Arne Birkeland).
  • Performance and memory useage improvements (Tridge).


As per usual PIDs are optimised for the 3DR/jDrones quad with 850 motors and 10" props. If you're using more powerful motors/props and are seeing bad flight behaviour in stabilize, start by turning down Rate Roll P in 25% steps.

Special thanks to our testing team lead Marco and the dedicated bunch on the 2.8.1 release thread who put their copters at risk while testing the pre-release version.  Some of their videos are here: 1 2 3 4 5 6 7 8

Please feel free to report issues you find in the discussion below and/or add them to the issues list.


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I'm new to this, just so I don't end up somewhere I don't want to be in the CLI, where exactly is the option to "enabling the "RAW" message through the cli"?


Many thanks




Mike, in the Terminal tab (CLI), once connected and you see "Arducopter v2.9]", then type "logs", hit enter then type "enable raw" and hit enter.

Cheers for that.

I've not yet upgraded to 2.9 yet, I was giving it a few days to see what I read in this thread first. However, I thought I might check the vibration levels to see if I have any work to do before I go through with the upgrade/ Currently my APM1 is supported on soft rubber grommets and I have bought some of that Gel sheet should I need to improve things.


Unless you have noticeable vibrations I would just balance my props, fly first and worry later. I put foam under my APM mounts and it made no difference.

I'll be following your advice first and spend tomorrow going over the prop balance, and perhaps look at better quality prop adapters. Probably a wee bit too much vibration and I'd like to reduce it was far as possible before I start looking gel sheet.

I agree, but I think oscillations in lift caused by a spinning propeller moving horizontally will always create problems even with perfect balancing. This high frequency (~2x Motor RPM) source of vibration is I think one of the primary reasons thin ACC lines are fairly easy at achieve at hover, but difficult to sustain beyond 25mph. There are some applications worthy of the broad performance envelope that foam and weight currently provides.

OT but related... IMHO APM3 should have a separated IMU board, mounted in a small foam sandwich, with a minimum number of very thin wires connecting it to the main board (essentially like Naza). If properly engineered (designed mass & material), it would make a big difference for a lot of ppl. Then hard mounting would work good on nearly all applications (again, like Naza).

ForIn English language parts of speech

What is ArdyFlyer? ;-)

As I am reading a lot of problems with vibrations here, I would like to share my knowldege and some findings I made to help people get rid of "bad vibrations"

- calm down and step back! Free your mind and try to take a fresh and overall look to your problem
- basics first! Start with the mechanical construction. Is it stiff and tolerance free? Tighten every screw, bold, whatever, double check it, try to bend the frame, shake it, listen for clickering noises. Everything needs to be super tight and stiff!
- keep your balance! Balance your props and motors. Check motor bearings and smoothness of the motors. Balance motors, spinners and props as a dynamic unit and do it super accurate. Throw away props with bend wings or cutouts!
- isolate! You cannot kill vibratons completly, but try to isolate them. Mostly the source are the motors and props, so decouple the motors from the motor mounts. Use stiff material with high tesion to keep the connection hard enough not to get wobbly
- smooth! Spend much time with your esc's checking timing, advance and cutoffs. Set them up to response quick, but smooth and strong.
- cabling salad. Fix your cabling. No loose connections are allowed, everything has to be tightened properly, no cable is allowed free, it could cause vibrations.
- mount hard! Fix all your electronic components as tight as possible to the frame, use rubber plates and double check not to bend the boards, ifmusing zipties. Check the apm to be fixed so it cannot vibrate around its center (imagine a guitar string, how do you stop it from vibrating?)
- hear! Use a long metal rod like stethoscope! Power up the engines without props and hold one end of the rod tomyour ear and the other end on the frame at different locations. How does sound change? In loudness, shape, try with all motors and seperate? You will find bad things quickly.
- be honest! If you really can answer ALL the steps where done and ALL found problems where solved, then - and only then you shall proceed to the last step.
- check the accel readings of the apm at different filter settings, tune your setup to Our needs and enjoy!

Consider this as a checklist, every step must be completed 100% before even thinking of proceed to the next one.

With regards

Thanks, and yes the metal plate is fixed to the case (1 layer black 3M outdoor 2 sided tape, complete coverage... pretty much like it's glued on). I figured after shaking the heck out of the frame with my hands and watching the case follow movements with good fidelity, I was fine as far as inertial response goes. On a CP heli though I'm not so sure, but the setup works fine for slower responding quads.

Although to be honest, I did have doubts about level going out of wack after a good jostle at landing or during transportation. So far I haven't noticed any ill effects from my mounting, but if I do I'll report on them here.

Here are my current params Leonard. I think you wrote the post that gave me the idea to play with higher I and Imax. I have gone back and forth and it seems the higher values removed some minor high speed pitch oscillations I was having. ;)


I'll take all the luck I can get with this multi-rotor stuff. I am not sure if it applies to CP helis, but I commented on my high speed pitch oscillations below.

This individual expands on the same video with some additional tips, great stuff!

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