Wow has this discussion gone off the deep end. Still a couple questions come to mind. If we're measuring differential pressure, it really doesn't matter if we're using total pressure or static pressure, differential is differential, but how do we verify the accuracy of those readings under the cowl? If you use single point probes, proper orientation of the pick up tube is critical. To accurately measure total pressure the probe must face directly into a laminar airstream. If we're measuring static, the probe must be exactly perpendicular to the laminar airstream. Inside a cowling there is the potential for very high airflows, much turbulence, as well as areas of stagnation, and most importantly airflow striation. And this is keeping it simple. The use of a picollo tube, (multiple samples in a linear area) might help some with accuracy, but you might also find that the orientation of this tool will yield widely varying results. The most accurate method my simple mind can come up with to approach any relative accuracy would be to install some sort of vel grid device over the inlet and outlet of the area in question. I'd speculate it's already been done, who knows, but in reality, this is really not such an easy project to get right, numbers is numbers though, and I guess even if they're not accurate, what's it really matter anyhow?
Cheers, Bob
