Without airspeed sensor how apm control the throttle

I have a question puzzling me for a long time!
If my apm board do’nt have an airspeed sensor, those parameters (such as TRIM_ARSPD_CM,ARSPD_FBW_MIN and ARSPD_FBW_MAX) still affect the flight or throttle output? if those parameters have no effect on flight, what kind of factor would affect the throttle output?

I believe that it uses the aircraft speed provided by the GPS.

It is a good question, and it should be in the docs. To start with I’ve added an FAQ entry for this question here:
plane.ardupilot.com/wiki/fixed-w … eed_sensor

Nice explanation, comprehensive and to the point.

thanks a lot !
I always worry about a stall in a long distances flight! So I have paid close attention to those parameters ,
thank you for your response ,now I do know how to deal with those parameters.

I have several airplanes that I have been flying for several years with no airspeed sensor. The computed airspeed is excellent and they fly just as good as my one airplane that has an airspeed sensor. It makes me wonder if it’s worth the trouble to install a sensor.

I think the only tome it’s really needed is for auto landings. With all the landing and stall prevention features maybe that’s no longer true. My runway is too short so I don’t do auto landings so I am perfectly happy without a sensor. As the FAQ says just use the TRIM_THROTTLE to set the auto speed.


It can get interesting with a nitro engine. I make sure and keep the MIN throttle above slow idle so no chance it kills the engine. For the trim throttle I flew manually the speed I like and then noted the throttle percentage on my gcs then set the trim throttle to that. I still use the SLEW rate too which helps prevent engine stalling when the controller increase the throttle. I have not flown in two years. I see there is stall prevention now, wow…