TruTrak ADI Plumbing

[szicree]

Today I put a some vacuum on my static system to check for leaks and had a big one. After isolating instruments one by one, I found that my Trutrak ADI won't hold anything. As I try to put a vacuum on it, I can actually hear the air going through it. What the hell?! Isn't this thing supposed to read vertical speed? It occurs to me that in a non-pressurized aircraft a guy could have a whopping-big leak in his static system and never even know it. I mean, when I put a vacuum on my static port, my altimeter registers the altitude but then indicates a rapid descent as the vacuum is lost through the ADI. If I were actually at altitude this wouldn't happen, so all would appear fine. Am I missing something here?

Steve Zicree
RV4 plumbing

 

[jbDC9]

You're talking about the static line connection and not the pitot line, correct? I'm looking at the installation section of the Install/User Guide... it says that in an unpressurized a/c there's no need to hook up the static line, just leave it as it came from the box. No need to connect it to the rest of the a/c static system. I'm planning on just installing a fitting with a smaller opening in there just to keep any big bugs out...

John
Houston
-8QB finish

 

[szicree]

I read that too, but what if it was a pressurized aircraft?? All of the instruments that share a static connection with the ADI would be reading cabin air instead of outside air. In fact, wouldn't my cabin be de-pressurizing through the ADI and actually sending air OUT through the static port? This just doesn't seem right and I think the thing must be defective. Any ADI experts out there?

Steve Zicree

 

[szicree]

ADI Update

I just got off the phone with the folks at Trutrak. It turns out that in the current version of the ADI, hooking up the static port is not just unrequired, but is actually not possible. The device will leak internally unless specially configured for pressurized aircraft. Their feeling is that in most non-pressurized aircraft, the cabin is an accurate source of static air. It's worth noting that this device is measuring changes in pressure rather than the pressure itself, unlike an altimeter. Obviously my problem is solved by just disconnecting my static line from the unit. Man, I wish I would have known this before I spent all day figuring out how to arrange all these hoses.

Steve Zicree
RV4 plumbing