After months of testing AC3.1 is finally available in the Mission Planner and GitHub.

Warning #1: If the vehicle is left landed (but armed) while in AltHold or Loiter mode for more than a few seconds, the vehicle may suddenly jump into the air the moment the pilot raises the throttle above zero.  The reason is the baro altitude may fall while the vehicle is sitting on the ground.  In AC3.2 this bug is fixed because we reset the target before take-off.

Warning #2: Motors will spin (slowly) by default as soon as the copter is armed!  You can switch this feature off by setting the MOT_SPIN_ARMED parameter to zero.

Warning #3: if you see "Bad Gyro" on the HUD then you may have a blown 3.3V regulator.  See this thread for details.

Warning #4: if you use a sonar set the SONAR_GAIN parameter to 0.8 or lower

Warning #5: Trad Heli users should now connect their main rotor ESC to APM's RC8 output

Warning #6: Trad Heli BUG causes loss of collective control in ACRO mode if swash type set to flybarred (i.e. not flybarless).  Will be fixed in AC3.2.


The major improvements over AC3.0.1 are (full list here):

1. Pixhawk support (Tridge & PX4 development team)

2. Autotune of Roll and Pitch gains (Leonard/Randy)

3. Drift mode (Jason)

4. Improved Acro (Rob/Leonard) and new Sport mode (Leonard)

5. Arming, Take-off, Land in Loiter or AltHold

6. TradHeli improvements (Rob) including:

a) support for direct drive tail rotors

b) smoother ramp-up of main rotor

c) reduced collective for better control in stabilize mode (STAB_COL_MIN, STAB_COL_MAX params)

7. Support for SingleCopter (Bill King)

8. Performance improvements resolve AltHold troubles for Hexa & Octacopters

9. Safety Improvements:

a) GPS Glitch detection (Randy)

b) Motors spin when armed (Jonathan Challinger)

c) crash detector shuts off motors if copter flipped for 2secs

d) batt failsafe option to RTL instead of LAND, gps failsafe option to trigger AltHold instead of Land

e) more pre-arm checks of inertial nav speed,

10. Bug fixes:

a) optical flow working again (although performance is still not great because not integrated with inertial navigation)

b) ROI working (use DO_SET_ROI command)


How to upgrade:
Click on the MissionPlanner's Initial Setup >> Install Firmware screen.  The version numbers should appear as "ArduCopter-3.1", then click the appropriate frame icon and it should upgrade as per usual.

Special thanks to Marco and the many beta testers on the AC3.0.1 thread who put their copters at risk during the testing of this new version and uncovered many problems so that you don't have to!  Here are some of their videos: loiter in wind, patio sonar, autotune, autotune2, roi, beach, acro, vrbrain, tricopter, train spotting, radio failsafe, the tree, double loiter


If you haven't seen it recently, please check out the ArduCopter wiki.


Feel free to post comments below and we're going to use the new APM Forum for support issues so please post your support requests there.

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Hello All

I am still trying to get my head around the whole launching in ALT HOLD or LOITER. My Quads have had battery upgrades (Larger batteries) and it now takes about 60% throttle to get off the ground to hover, i have adjusted the THR_MID to 600. In Stabilize mode, once at 60% if i click into ALT HOLD or LOITER, i start to ascend. my vibrations are well within limits (0-1 on X & Y, 7-8 on Z Axis)

what i dont understand is when launching in ALT HOLD OR LOITER the props dont spin until i get to 50% and it appears it will jump at any moment. I know most of the instructions say when you go into ALT HOLD or LOITER from stabilize your stick should be at 50%. but with a THR_MID at 600, that seems difficult. so what am i missing here, what do i need to change to get both THR_MID and ALT HOLD/LOITER to be in tune with each other?

I would prefer to launch in ALT HOLD and fly or in LOITER for certain times. the Craft is nicely balanced and they flt great in stabilize mode. any suggestions are greatly appreciated.

Hi, please post support questions in the forums:

EKF is not in any release. You will have to compile latest master or load it from a hex from

hi Jonathan, i would gladly post support questions over in the other forums but they always seem to go unanswered there. as i understand it, there is also a sizable back log and you are short on reviewers

@themightythor, pls check if your mot_spin_armed in Full Parameters is 70. When you arm the copter the motors should spin very slowly. If not,you have to redo your esc calibration. Now, if you launch at alt hold mode, it is normal that you have to bring the throttle stick to more than 50% to take off. Also, if you copter climbs after switching from stabilize to alt hold, you might want to lower your throttle rate P or throttle accel P. 

hi Willy and thanks for your help, i purposely have MOT_SPIN_ARM set to 0. i will Change the Throttle rates as you suggest, i believe they are at defaults. any suggestions for numbers? i was waiting for today to get some good logs to post. thanks for your help

Hi Just got my Pixhawk installed in a F800R hexacopter and first flights went well. but i noticed that after last flight gyros was offset by 15 for ex.  fwd pitch was 15 deg to the left...

Tried an autocal flight but aborted because it did not fly well when correcting. When I landed the gyro was slightly tilted in missionplanner.

Made a new compassmot and. Recalibrated gyros and then the gyro went totally crazy...recalibrated again same thing. Gyros are spinning, baro is crazy and gps is all over the place... se attatched video...Help!! 

Also the calibration went wrong file attatched


This is My XAircraft X650 with Log attached. it performed pretty well but still have some drift in Loiter. i am looking to fine tune this so that Loiter stays put. i have been trying on my own for weeks and by reading this forum, i have gotten close but not good enough. My THR_MID on this aircraft is usually 550 or 600. in this case it was 550. i have done all ESC calibration (XAIRCRAFT 30A ESC) and auto trim. the Log File for this one is 2014-30-31 10-24.log

This is my F450 also with Xaircraft 30A ESCs. this one is the one i have the most trouble with.

With Log File Attached, This one i can never seem to tune to get a nice steady LOITER or ALT HOLD, it always Rises. any help would be appreciated and thank you in advance. the Log File name is 2014-30-30 10-10.log


On your F450, try  lowering your Throttle Accel P from 0.75 to 0.6 and your Throttle I from 1.5 to 1.2.  By the way, the up and down behavior of the copter is controlled by the barometer in Alt hold or Loiter...Did you cover your baro with black foam to prevent the light and wind to get into the board?

On your X650, set your Loiter PID P to 0.2, and Rate Loiter D to 0.15...Try these values to get lock in loiter.

I have some issues with altitude hold as well - does the APM2.6 need more covering than what is provided by its case? The case is mostly black (but not completely opaque) and I know that inside it has foam covering the barometer - does it need more?




What i did was to cut a small piece of 3M black double sided foam and stick it on top of the baro. The baro has two small holes, make sure that the foam does not get inside these holes. Please take note that there are leds beside the baro and it will affect its performance if not properly covered. The soft foam inside the case may not be sufficient to prevent lights to get into the baro.

Thanks so much for your help Willy, it is greatly appreciated.

My baro is covered by what ever 3DR put in there, i have never opened the case for anything, nor have i ever had a horrible crash that would have moved it in anyway? the F450 always has trouble lifting off, i need to check the balance on it, it always wants to rear back and lean left (as you are looking at it from the rear) but i compensate by elevator and aileron movements. the XAircraft always seem to perform better even tho all three of my Quads have the same APM & ESC. the only difference is the Motors. i will certainly try out those settings and see how much that helps.

I guess i better look inside this case and see if the foam has moved in any way and then add some black tape to the top of the foam?

thanks again

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