******The venturi effect makes the pressure in the cabin lower than
the outside pressure.******

Not always, and particularly not in Paul's Cessna 185. These Cessnas have
two scoops on the aft fuselage that provide ram air to the cabin. The
slight
pressurization reduces the risk of exhaust entering the cabin.

Karl

I didn't know that. (Nice to know.)

I think Bonanza's must be the same, since I flew in a Bonanza once
that had a small opening in the side window which was closed by
a hinged flap held in place only by the higher cabin pressure.
If the cabin pressure were lower than the outside pressure as Ben
suggested there would have been no way to close that flap.
(I don't know if all Bonanza's have that opening - this was the only one
I've flown in.). Ben might be correct for most aircraft however.

From: "john smith"
Subject: Why a static port?
As I recall from my Physics classes:
PV=nRT

I don't think that equation has much relevance here.

~Paul