Pitot line leak at ADAHRS?

[rgmwa]

I'm just doing the pitot line leak test on my Skyview equipped RV-12. I'm able to confirm that the line is good from the pitot back to the ADAHRS connection because I have a backup analogue ASI in the line (nylon Tee fluid fitting). The pressure reading is rock solid when I cap the line with my finger at the ADAHRS end. However, when I screw the nylon nut onto the ADAHRS, I can't get better than about 50 seconds for a 10kt drop, which is well below the 60 second minimum acceptance value.

I've tried tightening the nylon nut finger tight, a bit more than finger tight, putting a little bit of O-lube on the fitting and threads (same as I did on fittings for the ASI tee, which work fine), a lot of O-lube, Teflon tape on the threads, re-cut the end of the line to make sure it was square, added an extra O-ring, replaced the fitting entirely, etc, all with the same result. I'm beginning to wonder if the leak isn't in the fitting on the ADAHRS itself or maybe an internal leak. Has anyone else experienced this problem? I know these units are tested before shipping, but is that a possibility, and if so how could I check it?

 

[Dynon]

It's rare but a possibility. You can create a pretty good seal against the pitot port with just your finger, so one imperfect way to check is to use the pad of your thumb and press it up against the ADAHRS' brass fitting. You should be able to hold pressure indefinitely pretty easily. If it leaks down like that, it's probably real.

 

[rgmwa]

That's a simple check. Thanks, I'll try it and see what happens.

 

[rgmwa]

Did the thumb test and traced the leak to the male nylon fitting that is screwed into the brass insert on the ADAHRS. Although the nylon fitting was tight, putting a little O-Lube on the threads fixed the problem. Thanks Dynon.