I wanted to clarify one thing on my previous explanation. Where I was referencing hole diameter and leaks was in the dynamic line itself. The hole size does not matter is all you are doing is putting pressure down a line to a sensor. It's a closed tube per say. Pressure is pressure. Blow into a 1" diameter or .1" diamter tube with a closed end. You'll get the same force. A static measurement must be free of pressure fluctuations in order to give accurate measurements. You'll notice in 99% of full-scale aircraft that static measurements are made with a pitot-static system that either has static ports perpendicular to the flow of airstream on a pitot probe or a set of static ports strategically placed on the side of a fuselage. About the only time they tell you to use static from inside the fuselage is if you need to break the altimiter instrument glass in an emergency, if the altimiter is stuck... Wonder if you can do that with the electronic EFIS's and still have altitude? lol

My opinion is that it is almost impossible to get good static measurements from inside a fuselage. I've got the experience and the data to prove it. You either have positive pressure or a vacuum and both can happen with an aircraft during flight. Especially if it is on a turbine aircraft.

Ohh, and you need to get a pitot probe far enough outside of the boundary layer (Several inches) in order to get clean dynamic air. It shouldn't flex or vibrate. Lastly, don't forget that humidity and air density also come into play! Enough variables? IAS is a good ballpark figure.

Michael