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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When I do it I do an erase and then use the compare parameters rather than load parameters to bring my existing variables back in. That way I can chose what to load and what not to.

Leonard. Great suggestion. Thank you

No, I think most of us have a laptop for that purpose.  You can buy wireless headphones, but Bluetooth has, at best, a 30-ft range.  RF Wireless headphones have a slightly better range, but to get a 100-ft or better range you will be spending more than $200.  For that you can buy a used laptop to run MP and take it with you.

The low-cost FRS walkie talkies might be a solution.  I would have to wonder if the talkie can handle a 100% transmit duty cycle.

Leonard - does the Channel-7 RTL override any mode settings set on Channel-5?


Yes. On my futaba 6ex I was able to use the TX CH6 toggle for RTL by plugging the CH6 off the RX into CH7 on the APM.

Just configure CH7 on the APM as RTL and you are good to go. (Test first of course.)


If I could recommend your post for a sticky I would. That info should be in the wiki under first time setup. The usage of PPMSum should also be listed before the description of using PWM connections.

Come to think of it, it would be great if the wiki had a "Beginner Setup" that walked through a setup using a recommended setup (use a power module, use an RX with PPM Sum, don't configure a throttle failsafe, dont configure RTL, set all modes to stabalize, etc). Then an "Intermediate Setup" with steps for using GPS with alt-hold. And then finally an "Advanced Setup" with RTL and auto modes.

Don't think it's acting like a ground plane but more of a shield. I know last year when I got my NAZA and MultiWii units to play with, I saw TONS of pics of people putting the GPS units right near the ESC's out on arms (UGH!!)

I tried that and it NEVER worked well (remember the DJI's have the mag & GPS in one unit!)

Anyways, alot of guys flying here in SoCal use this gizmo and my buddy bought me one.. NAZA GPS/ protector

When I met Chris at the AMA show this month, there was a vendor selling them there for $10.. well worth the investment!!

This is basically what everyone does... to shield from all the darn noise! If you've ever opened up a Align 3GX, Mikado VBAR, etc.. the cases are all shielded inside.. This was one big problem on the original 3GX's shorting out in flight with the pins inside.

I just covered mine with foil and the crazy tracks went away!

Shouldn't receiver throttle fail-safe be at 1/2 (not 1/4)  ie half-stick ?

Does anyone know who makes the yellow 20A ESC's that come on the 3DR hex kits, and what are their programming characteristics?

Just flew v2.9.1-rc2, most things seem well although it was only a short flight, will test more tomorrow. Did have one anamoly but am not sure if it's specifically rc2 or something else. I was checking stick response and at one point the quad seemed to "lose" or not update the right rear motor for a fraction of a second which caused the quad to jerk backwards and sideways for that split second but it reached 38° and then corrected itself.

Log Attached:


Boston - actually, there is a beginners page in the Wiki.  The Wiki is a huge source of information, but that is also its' curse - nothing is easy to find.

It's interesting that you say that.  I was hovering my 2.8.1 quad in the house two days ago, landed for a few minutes without power down, re-armed, and went to take off again. Rear motor ('+' config) twitched but would not spin even as I kept slowly applying throttle.  Other motors spun fine until quad start crawling backwards across the floor.  I was certain it was a loose connector or hardware failure, but taking throttle to zero and immediately back up again fixed the problem.  Have not ever seen it before or seen it since.


I'm using RDS with Splashtop on my Android. Sound is disabled on PC when connected and i get all speech on my phone and my bluetooth headset.

I even take advantage of all services in MP not simple HUD information :) 
Your wifi network is the limit of distance from PC.

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