APM Copter 2.9.1.b has been released to the Mission Planner and is also posted in the downloads area.
2.9.1b is a maintenance release incorporating changes to 4 default parameters that have been optimized since 2.9.1 was released.  There are also 4 minor bug fixes.  There are no code function changes or additional features.
The changes are:
1) reduce default INS_MPU6K_FILTER to 20hz
2) reduce InertialNav Z-axis time constant to 5 (was 7)
3) increased max InertialNav accel correction to 3 m/s (was 1m/s)
4) reduce yaw_rate P default to 0.20 (was 0.25)
5) bug fix for alt_hold being passed as int16_t to get_throttle_althold_with_slew which might have caused problems if you climbed over 320m.
6) bug fix for throttle after acro flip (was being kept at min throttle if pilot switched out of ACRO mode while inverted)
7) bug fix to acro trainer to do with roll correction 
8) prevent cli from being entered more than 20seconds after reboot.
Users are recommended to:
    Update Mission Planner to 1.2.41 and
    Update their flight code to 2.9.1b from the Firmware tab on Mission Planner. There is no need to go through a new configuration process in the Mission Planner.


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If you have a standard 3dr quad then, as you say, the defaults should be fine.

Pitch only being a problem could be because some of the ESCs are not calibrated, perhaps a motor has been damaged or the center of gravity isn't in the middle of the copter.

Just guesses...I'm not really sure.


     Thanks for the reports.  The RTL issues appear to be GPS glitches.  NumSats falls, HDOP climbs.  We've talked about possible solutions to this but we don't have anything immediately ready to try and deal with it.

I queried this as well. I was told that this function has been removed from Mission Planner as the Power module is auto calibrated so it is no longer needed. The battery voltage now displayed is incorrect, reading low by 0.3 - 0.6 volts.

I have been able to get my voltage reading roughly right be changing the divisor from 10 to 10.3.

This has been raised as an issue in github.






I was flying 3.0-rc5.  Switching from descend in ALT-HOLD or LOITER to STAB makes copter free fall immediately.  Apparently full throttle does not save if from 40 meter altitude and I hit ground.  That hurts.  Any parameters I can adjust to make it going higher throttle when  I put throttle stick to the top?

Had same thing with 3.0-rc3.

Also how I can make descent in ALT-HOLD or LITER faster than 1m/s?



Hi Christian,

Thanks for your info! this will help me making my Al enclosure faster :-D 

If you have any ferrite cores lying around, try to wind one as close to the servo box as possible

(at least 7 cm close (1/10 wavelength of 433 MHz) . and see if it helps to supress any RFI

(radio frequency interference). there are more solutions for your problem but this one is the most simple.


Thanks, Randy, for pointing that out.. Anecdotally, my events all occurred in the late morning..

Does the AL have to be grounded?

Grounded is better but you will see improvement even without grounding.

I just have time for test 3.0 RC5. Becauase, In Thailand have a raining everyday.

Frame : Tarot Quad 650

Motor : T-Motor MT4008 600KV

ESC : T-Motor 40A

Prop : 15x4

Battery : Zippy 4s 8000 mAh 30C

Radio : Turnigy9x Upgrade Frsky Mudule

Hover Time : about  24 - 26 mins.

The parameter PILOT_VEL_MAX controls the max rate of descent AND ascent in ALT_HOLD and LOITER.

Randy, on a related issue, any chance of having two different parameters (pos and neg) for PILOT_VEL_MAX instead of one for both? To be able to descend at a controlled but slowish rate and ascend at a faster rate would be a great feature.


it works the same as that rotating Al disc in your kwh meter (dont know the correct english word)

that thing that counts the electricity bill :-)  

We also call 'em meters, and they even read the same units (kWh). A few years ago our utility company upgraded everyone's meter to more sophisticated digital meters with adhoc wireless networking. So we no longer have spinning Al disks, nor do we have utility personnel visiting our homes to read the meters. Gas is the same way here... all new wireless metering. Anyhow, back OT. ;)

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