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Plumbing Static lines?

claycookiemonster

Well Known Member
I feel like I remember seeing a post saying that it was important (going-on critical) to plumb the two static ports with EQUAL length tubing until they met at a "T" to go to the instruments. I can't find any reference to doing this anywhere.
I can convince my brain either way: critical to equalize differing pressures in the event of a yaw state, or it doesn't matter since once they join, it'll all equal out.
 
I don't recall the requirement on the lengths, but there is a good recommendation to ensure that there are no "low spots" in the tubing that can trap water.
 
Simple fix to avoid any problem with different static line lengths. Put the T connecting the two static ports at the top of the nearest fuselage bulkhead. Then, run the static line from the top of the bulkhead forward to the panel. Problem solved.
 
I feel like I remember seeing a post saying that it was important (going-on critical) to plumb the two static ports with EQUAL length tubing until they met at a "T" to go to the instruments. I can't find any reference to doing this anywhere.
I can convince my brain either way: critical to equalize differing pressures in the event of a yaw state, or it doesn't matter since once they join, it'll all equal out.

There's no real flow. Length or delta length won't matter.
 
There's no real flow. Length or delta length won't matter.

In normal operation, true. In normal operation you only need one port, too. But the OP specifically asked about a slip, where, say, the left port was in a higher pressure area, the right in a lower pressure area. In this case there will be flow from left to right, and a pressure gradient along the line connecting them together. Without detailed knowledge of the slip-induced errors (are they equal but opposite?) it’s hard to say where you should tap in to get a true static pressure (although the middle is the obvious answer if you want improved readings for both left and right slips). My guess is that for most installations the port ID is significantly smaller than the tubing ID; the flow will be throttled at the ports, most of the delta P will be there, and it makes little difference where you tap in.
But tap in ‘up hill’ to keep water out.
 
I can't say that I'm smart enough to figure out if there's a slip error, but it seems like it would be pretty trivial if so.

However, water in the low spots is a real thing. In an effort to avoid that, I just ran them both up the nearest bulkhead then put the T at the top and came back down the pilot side of the same bulkhead. Probably added around 24" to the run.

I believe this is the way Van's calls it out, but wouldn't swear to it without going back into the print.
 
the pressure distribution model says that the center will be the average of the two port pressures. I plumb mine like this, and it also addresses trapped water.
 

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