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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Kieran: I can't replicate any problem on any of the copters I've set up with this build. What APM board are you using?

I am using APM 2.5. I am looking for ideas in how to get the official build installed. It's strange that I can build and install the rc5 version which seems to work fine but not the official install.


There is an know unresolved issue to be able to play Vimeo videos in Windows/IE10. Is there a way you could publish your videos on Youtube or some other universally accessible video streaming service ?




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.


Was there any specific reason to disable this in Auto mode?


Great job guys!!  I have been flying 2.9 today and everything seems very good. thank you very much to everybody that helped.

I do have one question, I have been reading through the new parameters, and one I cant seem to find is WP_LOITER_RAD, I have looked to try to find what its renamed to but cant seem to find it.  Is it still there?



2.9 is great....   everything I tested works well..


How come in Loiter my copter looks like its having a wank up there.....

It seem like every time a gps pos comes in it Jimmies around +-4 deg and does not go anywhere... like 1/sec or 2..

Its staying in the right spot no problem, but whats with all the wanking.... this started like around 2.5 and I keep

hopeing it would go away...


Eddie Weeks

oh... and as handcock says... "Good Job"


Are you using an official 3DR APM 2.5? (Some of the clones aren't detected correctly). If so, try reloading the code. 

Hey guys,


Already need help with the new firmware 2.9...


Don't know exactly what happened, but when my copter is on a level surface, the artificial horizon is not level and is leaning to the right; so when I take off, the copter immediately rolls or leans right.


How do I reset the APM2.5 board to level again?


I attempted to use the Arducopter level in the Mission Planner and followed the instructions to calibrate the accelerometer; but when I go to the flight data screen, the artificial horizon is still leaning to the right.

As far as I know it's official. It came from coolcomponents in the UK. I have reloaded the official code at least twice but happy to try again.

My quad survived all the upgrades from 2.1 to 2.8.1.

But no luck with 2.9. Loiter worked but quad was very busy making constantly small corrections. Alt Hold seemed to work fine but then the rear two motors dipped slowly and the quad crashed. Two broken arms and 1 prop...

Log Download button in planner just responds with "Error opening comport"

if no change in 2.9 try to maintain full  throttle down full rudder left for 10 15" to recalibrate or preflight calibration in pickup list  in flight data -> action panel - do action ...

Had to dump the log from the CLI and copy/paste into  a txt file. Hope the format is digestible (and that it is the correct log). Thanks to anyone having a look a the log.


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