Error : THR channel Out in Auto mode Zero

Hi all ,

come back again with Question that I think It will solve my problem , 

I connect My pixhack system with GPS as RC receiver and connect it to Mission planner , 

ArduPlane V3.4.0 (3aa9eb0c)
PX4: c4f39028 NuttX: d48fa307
PX4v2 002E0034 31345102 31353532

and I display in the HUB some items like altitude ASL and AGL


Throttle In channel : ch3in

Throttle Out channel: ch3out

Throttle precent % :ch3precent

As the mode is Manual , I get the same value of THR in and out ,

in STAB mode , I get the same value with little different 

But when change to AUTO mode or LOITER , the THR in is correct and THR out is zero (1100 pwm )

and in the message tab below And also HUB display this message "Executing nav command ID #16"

see this picture captured 3691272383?profile=original

in stab mode :


In auto mode

3691272400?profile=originalin loiter mode :


I think there is some thing that lock sending power to ch3 THR ,

I am not using Airspeed ,

maybe you will see the ch3out is depend in airspeed , or maybe home altitude,

I test it before and always Thr off when change to Auto ,

What is the parameter related to this issue ?

How to unlock the ch3out ?

How to set throttle manual control in auto mode ?


I hope this time my problem start to be clear .

I appreciate your efforts to help in any useful information.


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  • Developer

    Executing nav command ID #16

    is NAV_WAYPOINT.  The plane is executing NAV_WAYPOINT meaning its flying to a waypoint in your mission.

    Thanks, Grant.

    • why I throttle goes full ?

      and why plane can't keep itself in waypoint path ??

  • Keep in mind, in loiter or auto modes, APM will not listen to your throttle inputs at all, so it is irrelevant what your TX throttle output is.

    Is this a ground test?  Its possible that throttle is not being powered due to the APM thinking it is on the ground.  What is nav command #16 in your flight plan?


    Check your TRIM_THROTTLE parameter, make sure it is a non-zero number.  Also check RC3_REV parameter and try reversing it possibly (I had seen that helping someone else with a similar issue).

    • James , what about auto mode with manual throttle ?

      yes it's ground test , and today I did test with car and clime to hill , with fixed airspeed but I couldn't understand the problem the throttle is work when I move fast and change depend in wind as I think while the airspeed reading values 2 to 5 in ground , 10 - 17 in fast driving ,

      I checked RC3_REV parameter and throttle works with 1 and also -1 but not sure is it OK or not ,

    • I didn't know there was an auto mode with manual throttle.

      Your second sentence is very difficult to understand.  Are you saying your barometer (altitude) is working correctly with airflow over your fuselage?

      Are you saying that throttle in auto mode works now?  Did you try switching RC3_REV and attempting an auto flight again?

      I don't know of any other parameters to check.

    • James I did a test fly with RC3_REV  = -1

      when switch to auto thr rc3 out is always 1900 which mean full throttle


      and plane can't control itself in the waypoints path, 

      and if RC3_REV = 1 throttle output is always 1100 which mean 0

    • what items in log will determine the problem ?

      there are many altitude under items in log file as attached image

      log item.PNG
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