Stupid Static Port Question

[E_Dawg]

Can someone explain how static ports are able to take an even remotely accurate reading of static air pressure? I mean, wouldn't the airflow over the port lower the pressure siginificantly below that of the ambient air?

[pscraig]

I've thought about this myself, and with the help of my physics professor, have come up with this: the side of the fuselage is simply the best place on the airplane to take a static measurement. On the front, there is ram air compression; on the rear, much lower pressure; the wings have their obvious pressure differentials. We also indentified the need for a smooth airflow past the static port for steady readings, which also favors the side. The length of the tube connecting the instruments to the static port would seem to matter as well, all favoring the side of the fuselage near the cockpit. It may not be the perfect place, and the slipstream may cause but as long as that distortion is known and be compensated for, it is not a factor.

There are likely other factors I missed, and I'd welcome any additional info.

[E_Dawg]

</font><blockquote><font class="small">In reply to:</font><hr />
on the rear, much lower pressure; the wings have their obvious pressure differentials

[/ QUOTE ]

What about those Piper / Katanas that have the combined pitot / static tube? The pitot port is on the front, a drainage hole is on the bottom, and the static port is on the rear. Ugh; who knows....

[pscraig]

Hmm....I would think the static port would be far enough away from the wing to be affected.