The title says it all. Which of the two shield mounted air pressure sensor ports is to be tubed to the static pressure tube? The A/C testbed is a very slow flying foamy - 12x8 prop geared down to 6:1. Trial and error results are indeterminate possible because because of the low airspeed.
Thanks for helping to fill in this last dot.
Not sure if the APM setup is different (I have an original ArduPilot), but according to the AP(L) manual...
Connect the other end of the tubing to the nipples of the pressure sensor on the expansion board. The active tube goes on the top and the static one goes on the bottom.
If you are using ArduPilot in an aircraft with the propeller in the nose, the active pitot tube must be mounted out on one wing, at least a foot from the fuselage to be outside the prop flow. The passive one can be anywhere.