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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  • Reading about all these runaways...there seems to be common theme.


    GPS signal lost

    -as displayed in logs

    -yet people swear they had full GPS signal.


    Control Loss

    -lack of control - inputs not responding

    -full speed ahead to some unknow direction


    Waypoint issues

    -wrong RTL - usualy to some way off location

    -again people swear their HOME was set before launch.


    Which begs the there something up with the new code, that causes the APM to maybe freezeup, time functions and all?

    -intermittent glitch?

    -prolonged loop?


    -maybe the CPU is getting overloaded at some point and causing slowed execution?



    Just throwing some ideas out there. 

    It just seems like were it could be more than GPS loss.

    Could be wrong, but I don't remember hearing about this issue in 2.8.1



  • Bad crash on first auto flight with quad, APM 2.0, mtek gps, and 2.9.1.  I had flown 12 flights (~120 minutes) in stablize successfully.  I'd even gotten used to RTL yaw nose to home.  I then decided to test auto.  I entered an 4 waypoint mission.  I took off and switched from stabilize to auto.  The quad started to the first waypoint and then started acting "weird."  The best I can remember it started yawing.  I was worried so I switched back to stablize mode to try and gain control.  I did regain control but II couldn't tell the orientation so I switched to RTL so it would come back.  From the recorded video, it looks like it it yawed CCW about 90 degrees and then took off backward at a high rate of speed, it seemed like full throttle.  It was also descending on a roughly 3 degree angle.  I switched back to stabilize to try and stop the decent and to gain control again.  This did not help.  I had no control of pitch, roll, throttle or yaw.  It hit a fence.  The good news is that I only lost the frame, one motor and four props.  I'm still a novice at trying to analyze the logs so I thought I'd post them here in hopes that Randy or others can figure out what went wrong.  I'd flown similar missions before on 2.8.1 with no problems.

    2013-02-10 17-30 1.log

    2013-02-10 17-30 2.log

    2013-02-10 17-30 3.log
  • I am aware of the role of sonar now with 29.1 and its use in "terrane following".. How do I activate the terrane following feature?


  • Copter now flying really nice is all modes but would like to soften its auto flying a bit. I cant fault its tracking. The blue line is smack over the yellow one most of the time but its jiggyness is more than my camera gimble can cope with. Also at waypoints it has a minor fit before setting off for the next one. (even if its straight ahead)
    By default NAV WP ‘D’ is zero. Am considering playing around with that. Has anyone much experience with this?

    Is that another thing that will be completely different in the next issue? If so perhaps I should just wait. Do we have a rough ETA for 2.9.2.?

  • Hello!

    New to Arducopter 2.91. Great features so far, but please, tell me how to resolve the issue with wrong altitude in MP, it reads -2mil meters altitude. On Alt hold rises up enormously, GPS position works fine, on RTL only lands. I have it all in case, baro tests are working fine in CLI. Acc level done as in procedure. Autotrim done as in procedure. 3 pos switch on my Turnigy 9x has been set for flight modes, as suggested.

    Tx in advance!

    ps Sorry if I wrote something wrong...

  • I just ordered a tiny GPS tracker from Aliexpress.

    After lost bird just send a SMS to your SIM card in tracker and get an SMS with coordinates b4 you pick it up (the rest of it).

    20 gram only.

    You need a lot of luck with a name label, if somebody even find it.

  • i see mention of ver 2.9.2.. has it been released..

    if so where?


  • Sorry if these have been answered before, Ive just got back from 3 week biz trip and now see the hundreds of post!.

    Does the level work still when holding the yaw hard to the left for 20sec?

    Why has the option to revers throttle and pitch check been removed from the radio calibration area in MP? This is annoying when using the same radio for various aircraft when its much easier to set the firmware to suit.

    Is it possible the developers could add a "save" button in Arducopet Config page so its quick to save each time we make an adjustment to the PIDs? Also would be good of ArduCopter Config was its own item rather than a sub menu of Standard Params. The clicking back and forth drives me nuts on my slow field lapy

  • Cool, finally managed to get out to an open field to test the new firmware and have to say that despite the wobbles I was getting in loiter mode the accuracy of both loiter and RTL was infinitely superior, very pleased with the results even in a mild breeze it was coming down to a 2m hover 5-10ft from launch/arming point


    Loving it, well done you guys


    My set up is an Xaircraft X650 (original) with Xaircraft motors (35xx 890kv) turnigy plush 30a esc's

    I haven't changed any of the PID's it flies just fine as they are, sporty, powerfull and accurate like it's on rails

  • Guys anyone can check my log file and how to analyze it?

    2013-02-09 20-04 39.log

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