FWBA - Throttle issue - Limited throttle output.


Im currently working with ArduPlane 3.1.1 on an APM2.5 in a XUAV Talon.

I was looking at doing some autotuning; however, I wanted to test the system in FBWA first.

My understanding is that throttle control is manually controlled but bound by the THR_min and THR_Max. However, the throttle doesn't seem to be working correctly.


Ch3 (throttle) IN = 995 (low) to 2015 (high)

Ch3 OUT = 995 to 2015


Ch3 (throttle) IN = 995 (low) to 2015 (high)

Ch3 OUT = 973 to 1099

The THR_PASS_STAB is disabled. THR_MAX = 100 THR_MIN = 0 This was tested in a static / bench test.

Am I missing something? or is there a parameter that is not set right?

I am using an airspeed sensor; however, my understanding is throttle output in FBWA is not dependent on airspeed.

Thanks in advance.


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  • Have you changed any of the following parameters, THR_PASS_STAB or TRIM_THROTTLE?  I had a similiar problem and it was the TRIM_THROTTLE parameter.  This is assuming that you have calibrated the radio channels correctly.

    • I believe I have calibrated the radio correctly.

      The THR_PASS_STAB is disabled. It correctly does the pass thru if enabled.

      I will have a look at the TRIM_THROTTLE figure.

      Do you know how this affects the FBWA throttle?



    • I had a look at the TRIM_THROTTLE figure. This is set to 45 or 50% which I is the approx. throttle input (half throttle stick) required for a cruise on the Talon. Im not sure how this feeds into the throttle control in FBWA.


    • Ok well that seems about right the.  Does your RC3_trim and RC3_max correspond to where your ch3 max value of 2015?

    • Bingo....

      Thanks Chris... I did have a look at the RC3 max value at this was definitely wrong (was set to 1099) which was the maximum figure I was seeing.

      Not sure what this was wrong. Had completed a radio cal previously but possibly stuffed up it up sometime since.

      Now to have more fun with autotune. :)

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