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Replacing the pitot line

CAVU Mark

Well Known Member
I am still troubleshooting but have the gut feeling I have a faulty line from the pitot tube to the ASI. Has anyone replaced the line and if so how? The line used in my 3 is a soft pliable hose and since I did not build it am unsure how it is secured, if at all, in the wing. I do have wing tanks and original, unmodified, wings. Thanks.
 
I completely gutted an RV9A Pitot static system, end to end... Hoses, connectors, adapters, pitot and static ports (Dynon AoA). Solved a multitude of issues and flying around I don't even think about it anymore.

Perhaps consider removing your ASI and testing the pressure integrity of your pitot line to confirm your suspicions. I had access to a proper pitot static testing unit but I believe there are more rudimentary methods contained in the manuals for the other RV models if you don't have calibrated tooling at your disposal.

The long and short of it -> Peruse Van's engineering docs to get an idea of the routing (Did they even show anything on the 3?), get access where possible, push/pull on the tubing wherever you can to get an idea of the available movement and stiffness, disconnect the pitot or ASI end, poke some holes into the tubing end with a scriber and tie a long, strong, waxed lined into them (polyfibre etc), pull the tubing through in sections at a time dragging the waxed line through the airframe, poke holes in the end of the new tubing, tie the waxed line into it, consider using some inert Dow Corning type grease to lubricate the new tubing, pull the waxed line slowly back through working a section at a time. Don't rush, curse often and stop at regular intervals for a beverage of your choice.

Is that what you were after?
 
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Like OZCleco states, identify problem first.
If line replacement necessary, remove the old one. Removal of tank may give access to line, since it could run behind the tank.
Some ideas to be found in this thread https://vansairforce.net/community/showthread.php?t=176642 to install/secure a new line.
Last tip, the use of press-in fittings (Steinair, ACS, etc) greatly facilitates connections.

Good luck!
 
It all depends on how the guy built it, Mark. Being an experimental, he could have done anything. Although, I'd be surprised (or maybe not :eek:) if he ran flexible line for the entire length so your problem is probably at one of the joints/connections. Is the pitot tube itself removable? My -3 had a Piper style pitot tube mounted under the wing with an inspection panel nearby with flexible connections and soft alum tubing running through the wing.

You prolly know the trick of pushing a length of soft tubing onto the end of the tube and then rolling the end to create a slight positive pressure to check for leaks. I've haven't tried it myself but it makes good sense.
 
I am still troubleshooting but have the gut feeling I have a faulty line from the pitot tube to the ASI. Has anyone replaced the line and if so how? The line used in my 3 is a soft pliable hose and since I did not build it am unsure how it is secured, if at all, in the wing. I do have wing tanks and original, unmodified, wings. Thanks.

The 3B drawings show the pitot tube as 1/4 aluminum tube through snap bushings. I am not sure if you have the plans so I will attempt to attach copies as pdf.

As others have said yours may have been built different, obviously with soft hose to start with but maybe otherwise to the plans...

Good luck,

Russell
 

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Problem solved

Actually no problem, operator error. The soft hose attached to the pitot tube is the point were it leaked. I "assumed" it was good since I used 2 clamps but did not check it. I removed the ASI and blew up a balloon. Pressure held for hours. Rechecked the ASI with water psi and a manometer and voila, accurate to with in 1MPH. Hard to believe.

There is a rigid line cemented onto the lightening holes in the ribs. I would not want to replace that, possible but not fun.

Thanks for the input.
 
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