ArduCopter 2.9 / 2.9.1 released

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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  • Fly Away's does also happen to DJI

    Norwegian photographer lost his DJI Phantom with Gopro3 on his second flight.

    Been talking to the guy. He told me that he calibrated compass prior flying (both times).
    He also waited 1-2 minutes before takeoff and was sure he got a gpslock.

    Short after takeoff he lost radio contact, the quad went south/east, and the radio alarmed.

    So my theory is that the radio some how went off and the home point was never locked/sat during those two flights and the quad went home to china. Strange anyway.

    Unfortunately he did not connect with USB and Naza Assist software to check all settings. The supplier told him just to charge and go !!??

    Her is the article

  • please help me

    im try test arducopter with chinese ublox 6m (without 3dr config file)

    its detected and show 3d fix and correct lat & lon (but hdop and satcount wrong)

    but in loiter mode quadcopter do not resist to the wind!

    at the log  line 2148 am enable loiter mode but below ntun mesages show zero in lon & lat error

    i try to find in source code howto satcount or hdop affect to alt_hold and I find nothing

    2013-03-03 18-25 2.log
  • I am expierincing problems with Alt-hold too.. I have a HAL quad with 1400kV on 4S and in stabilize it all works ok, hovering at apprx. 40-50% throttle. When I flip Alt-hold (or loiter for that matter), the quad immidiately goes balistic at full speed (to my opinion). It's at 30 feet in a flash and I don't dare to let it continue without intervention, so switch back to stabilize and bring it back down without problems. 

    I've included the logs, hopefully someone can help me out here.. :(

    btw, I've had the same problems with and without sonar enabled. The baro sensor is covered with cloth and under the canopy, just like in the old quad.

    btw2: this board has performed ok on my old quad, but I needed a bigger one to carry a decent cam.

    2013-03-05 15-05 1.log
  • Is -5 to -15 still considered acceptable for Z Accel vibration when running 2.9.x?  After balancing props and motors I am within that range but just barely.  I have not yet done anything to isolate the APM from frame vibration.

  • Problem with Futaba and PPM..

    Out of necessity, I am using my older JR 10x with 2.4 XPS module for control but really like my T8FG.. When using PPM 2.3.16 flash with my R6203SB and T8FG, I get nothing in radio calibration.. Tx setting are MULTI, rx set to normal speed..

    I get perfect function with my FrSky 4 - T8FG and XPS nano - JR10x with positive going PPM.. Is futaba PPM negative going? This 6203 works fine with the Vbar in PPM.. 

    This is nuts, it should work.. What am I missing?

  • I had a chance to fly my quad over the weekend to gather additional Accel Z data. The purpose of the test was to see how well the foam ear plugs dampen vibration when subjected to the cold. The 6 minute flight was conducted with temp = 25F and over 10,000 continuous data points yielded a standard deviation of 1.46 acceleration in the Z axis. MPU6K_FILTER = 20.  Looks really good. This will be my standard design for mounting the APM.  Details of the mounting can be seen in the DIYD Vibration Control Wiki. 
  • I can get Y4 in this version?

  • T3

    Hi guys,

    I posted this in the APM 2x forum but no response, thought I'd hop on a thread with a lot more eyes on it. Recently upgraded to 2.9.1 and now when I use altitude mode (or guided or any altitude controlled mode) and move the quad at a moderate pace it climbs like crazy. As soon as it stops it figures things out and then descends. If I disable throttle accel it seems worse. Any ideas? 

    Here is the original thread with logs: 

  • Silly question, but how do I turn raw data logging on/off so that I can see Accel Z values?

    Thank you.

  • Tuning Question

    During straight between waypoints my quad twitches a but in pitch and roll (more noticeable in pitch). What do I need to adjust? Loiter is excellent.

    Also it seams to slow down and takes a while to hit a waypoint. That is worse with higher WP Speed. Changing WP radius has no effect on this problem. Seams to be worse going into the wind.




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