Water trapping
Have you considered that the arrangement described above can create a condensate trap between the "T" and your instrument panel? If the "T" is placed as low as possible, near the left static vent, the water trapping geometry is minimized if not eliminated.
But the condensation is another consideration. I'll have to put some thought into that. What are the chances of condensation forming in those lines and have there been any accidents, etc. as a result of a blockage caused by condensation?
I've also given a bit of thought to the water trapping issue. Here are some points to consider:
Firstly, a good question to ask is "in what way(s) would water enter the tubing in the first place?" I could see two possible ways: 1. liquid water entering the static port under positive pressure (weather, airplane wash, etc.), or 2. condensation forming in the tubes, as Bill describes. While both are theoretically possible, I don't know (I would like to know) if either really occurs in practice. On every preflight I diligently drain the pitot & static drains in the Cherokee I fly, and to this day I've never seen a drop of water (although I live in Southern California, where we don't have a lot of moisture). So, has anybody ever known this to be a real issue?
As far as solutions to this alleged problem: If the concern is liquid water entering through the static port under pressure, then having the "T" as high as possible on the bulkhead as Phil describes would give the best measure of protection against the water entering in the first place. If the concern is condensation however, then that can happen anywhere along the length of the tube, so the only real solution would be to provide adequate drainage. Having the "T" below the forward tubing run as Bill suggests would provide drainage for the very aft part of the tube, which is good. However, there are still likely to be other low spots in the tube further forward that could trap water. Specifically to the -7A, the forward canopy deck slopes down toward the panel, so there will be a low spot in the forward cockpit. Likewise, the pitot line and any AoA pressure lines coming from the wing will inevitably have a low spot at the wing root due to the dihedral angle. There would also likely be low spots in the tubing between the instruments. So if condensation is a real concern, then every one of these low spots in the tubes would need a drain. That seems a tad impractical.
I've asked the question before about whether people have installed pitot and static drains in their RV's, and the overwhelming answer was "no, and it's never been an issue". So before I'd go to the trouble of installing drains, I'd like to ask that question again. Has anybody ever had condensation or any other kind of water intrusion or trapping problem in the pitot/static tubing in an RV? Has anyone found that low spot drains really are necessary?
