Involuntary (Pneumatic) Leak Test

On Thursday evening I had some visitors that wanted to see the plane. A 17-year old boy named Patrick who wants to study Aeronautical Engineering was the driving reason for this interest.
Among other things I also wanted to give him an idea of modern experimental avionic systems and so I fired up the Skyview. He was impressed and even more so as the SV showed a constant airspeed of 59 knots. Whatever I did did nothing to change the airspeed and I was getting seriously worried that I would have to replace the ADAHRS unit again.
We even (lightly) blew into the pitot tube to see if was open and yes, it did increase the airspeed but only to settle back at 59 knots when we stopped.

What was this?

Well, that night I was too occupied to show Patrick everything he wanted to see and I delayed the troubleshooting till the next day.

The solution occurred to me while I was at work. I remember that I had previously plumbed up the ADAHRS and I had even posted this a few weeks back on the blog. That by itself was not the problem though. What I had forgotten during the plumbing was the fact that I had still tape over the static ports as I am still worried about mud daubers clogging up this vital ports.
Now with the tape in place and the static system hooked up, I had created a closed system that changes pressure with the ambient temperature.
When we looked at the Skyview, it was night and bit less hot than on the day I sealed the system. This naturally causes a slight vacuum while the pitot was still measuring ambient pressure. Now the pitot pressure was greater than the static pressure measured by the SV and that must show as airspeed.

Perfectly normal!

I was anxious to get home and confirm my theory by removing the tape from one of the static ports and sure enough, the speed went down immediately from what was then 29 knots. It was much warmer than on the night when we saw the 59 but less hot than on the day I sealed the system.

This also means that this static system had gone through quite some pressure cycles and did obviously not leak enough to come to equilibrium with ambient pressure.

I think this is a great low leak rate and therefore I have involuntarily tested the static system. I will stil perform a formal test though but I am very confident that this will just verify what I have already determined.