I use to fly a Skywalker X8 for AUTO mission with with an onboard Pixhawk and the last artduplane firmware, and I'm still struggling about the best way to have a reliable airspeed. On the one hand, I flew once without using any airspeed sensor, and the plane stalled because of a wrong over-estimated the airspeed. On the other hand, after having installed, calibrated and flew once successfully with the pitot tube coming with the pixhawk, I nearly got a second crash since the airspeed sensor was far underestimated. In the latter case, I guess that the tube was obstructed, maybe by snow (the area was snow-covered). So far, I used to blow into the tube (not directly) to have a rapid ground-check that the airspeed is working, but I'm now wondering whether this is good idea or not since this can obstruct the tube with water, which in turn might freeze in flight at low temperature. Does anyone have a good way to check the reliability of the pitot tube on the ground? Any general tips for improving the reliability of the airspeed sensor is welcome.