It appears I have a slight leak in my pitot system (rolled tube over pitot test). I have a 56 C172. Do these have the flexible tube at the wing root? If not are there any other prime candidates? I'll find out about the wing root tomorrow. Just wondering if anyone knew off the top of their head.

Thanks.

Frank

These leaks can be tough to trouble shoot, do you have access to a test box still? has anything been disturbed recently behind the panel? Ive seen instruments leak, fitting going to instruments leak, the plastic tube split and the moisture collectors crack.

I had the same problem, also a 56 C-172, it was a crack in the tube where it bends down 90 deg. at the door pilar/edge of the windshield, and it appeared to be very old, possibly cracked when the tube was bent at the factory. Fixing it did not have any change indicated airspeed

I remember some rubber hose up in the wing root.
Loose fittings.
Loose connections
Corrosion on aluminum lines in wings
Either way disconnect it close to the airspeed to eliminate everything in the doorpost and wing. If it's not behind the panel then keep moving out towards the pitot until you find your leak. A rolled up tube is as good of a test as anything.

Leaks can come on for no good reason. My airplane's pitot static system was replumbed 12 years ago, then again 4 years ago by a different shop, which said that the previous replumbing was done improperly (how am I to know?). Then last month a new leak showed up which had to be tracked down--apparently found in the tail cone, where the static ports are located. Looking at the tubing and fittings, I'm not surprised--not exactly tough appearing parts.

Cary

One organization I worked with for a while had a helium detector to troubleshoot pitot/static systems. They had dozens of instruments connected to their pitot plumbing at times, and a helium detector could locate the tiniest of leaks within minutes. They pressurized with helium to about 1psi and then used the detector wand along all the compartments of the pitot runs. It is a very sensitive test.

Once the area of the leak was found with the detector, the soap bubble test located pinholes.