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've just updated to 1.2.31 using the MP and now I dont get any live data on the Flight Data tab.  Only the ARMED / DISARMED and the flight mode writing changes - everything else is dead...

Thank you for your reply,excellent response as usual,Marty.

Andre how come you have 1.2.31?? As latest is 1.2.32, so please run update again to see if you get higher version. It also might be that you accidentally have APM1 software on APM2.x board or vise versa. 

After Upgrade the Mission Planer 1.2.31 this Message logged in ardupilotplaner.log. In the Repository I found Version 1.2.31 not 1.2.32


2013-01-19 11:31:57,525 DEBUG ArdupilotMega.MainV2 - New file Check: 14 vs 14 "13772047c153093bbdd3eb5d6421fc41" vs "13772047c153093bbdd3eb5d6421fc41" (:0) [ProgressReporterDialogue Background thread]
2013-01-19 11:31:57,525 ERROR ArdupilotMega.MainV2 - Exception during update (:0) [ProgressReporterDialogue Background thread]
System.IO.IOException: Der Prozess kann nicht auf die Datei "D:\Mission Planer\" zugreifen, da sie von einem anderen Prozess verwendet wird.
   bei System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   bei System.IO.File.Delete(String path)
   bei ArdupilotMega.MainV2.updateCheckMain(ProgressReporterDialogue frmProgressReporter)
2013-01-19 11:31:57,525  INFO ArdupilotMega.MainV2 - Starting new process: D:\Mission Planer\Updater.exe with D:\Mission Planer\ArdupilotMegaPlanner10.exe (:0) [ProgressReporterDialogue Background thread]
2013-01-19 11:31:57,556 ERROR ArdupilotMega.MainV2 - Update Failed (:0) [ProgressReporterDialogue Background thread]
System.ComponentModel.Win32Exception: Der Datenträger einer Datei wurde extern so geändert, dass die geöffnete Datei nicht mehr gültig ist
   bei System.Diagnostics.Process.StartWithShellExecuteEx(ProcessStartInfo startInfo)
   bei System.Diagnostics.Process.Start()
   bei ArdupilotMega.MainV2.updateCheckMain(ProgressReporterDialogue frmProgressReporter)
2013-01-19 11:32:15,917  INFO ArdupilotMega.Controls.ProgressReporterDialogue - DoWork Done (:0) [ProgressReporterDialogue Background thread]

Noted n TQ Marco

Thanks for the explanation Randy, its a relieve to know that we only need to do it once and savable :)

Prefer the the 2nd rush,no clock ticking

I have a similar problem since 2.9. No problems with 2.81. No sonar, ubloc gps, stabilize works fine, however once in loiter, if I climb, it wants to keep climbing, if I command a down, even full down it takes about a second to start down, then it comes down hard, try up again, it responds about a second later climbing fast, impossible to control alt in loiter. I watched the videos, calibrated and changed the throttle and alt settings, any suggestions, thanks........Don


I have the "error opening comport" in MP 1.2.31 (and also before)

To recreate the error.

1: Open MP

2: Connect to APM in Flight Data tab

3: Click Terminal

4: Wait until you have the Arducopter V2.9] prompt

5: Click "Log Download"

Console output:

That's not quite the word I would use to describe Loiter LOL, but it I suppose the behaviour could be described that way. Likewise I had hoped that the jerky Loiter would be gone now but with my quad I'm sure it's actually worse. It twitches and wiggles with small corrections the whole time in Loiter. Bring on v2.9.1!

Having flown a couple of packs this morning I can't fault v2.9 except for the jerky Loiter, the Alt Hold is quite remarkable, Auto was fine and RTL good too, TakeOff and Land commands really good, amazed how the well 'Land' works, as the quad touches down the motors go slow and then stop, no more bouncing - impressive!

Kudo's Dev Team!!

Where did u find 1.2.32????on my windows XP only 1.2.31 after few update try....

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