Can't understand airspeed control

I've been doing some flights to test how APM 2.73 manages airspeed.  I'm using a Bixler 2, which is a pretty slow airframe and can be blown backwards at low throttle settings.  I have a 3DR ArduPilot 2 kit with GPS and Telemetry, and an Airspeed Sensor.  All testing was in in Auto mode, flying a large loop repeatedly.  What I was hoping to accomplish was this:

- figure out how to set a minimum forward ground (not air) speed, so that the plane will increase its throttle before it is blow backwards and off course

- failing that, figure out how to set a minimum air speed, so that at least I can set that value above the expected wind speeds

I looked at the min/max/cruise airspeeds in the PID panel, and the MIN_GNDSPD_CM parameter.  I tried cranking up values for all of these, but I couldn't see where any had an effect on the speed the airplane was travelling.  I could hear that the plane was controlling the throttle up and down, but always to the same speed, about 10 m/s airspeed.  I also tried switch the airspeed control algorithm from 0-default to 1-dont use airspeed and back.

Is there something I'm missing?  I've attached the .tlog from my test flight (zipped), the corresponding .params file and a screenshot of my PIDs screen in case anyone can use those to figure out where I've goofed.  Thanks!




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  • 100KM


    Have you discovered how the min/max/cruise speeds are controlled?   I have noticed the same thing with 2.71 and 2.73 on an APM2.0.    I also noticed that I cannot nudge airspeed with the throttle in FBWB either.  

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