Static System tubing information

[skip]

I am well into my rebuild of the wings on my 1946 BC12-D. I have a question about the tubing used originally in the left wing for the pitot tube and the static line.

The plane is a 1946 BC12D sn 7700 with the Gilbarti/Harrer STC converting to an 85 HP BC12-D-4-85. The wings got hailed on a couple of years ago, and a hairline crack in the spar from under the root plywood sealed the deal on a complete rebuild.

The wing was certainly played with in 1973 when the STC was applied with the new spar root bushings and the modifications to the strut attach fittings. The aircraft was mostly dormant until the early 1990s when it was recovered with Stits. There is no history of any modifications to the static system. The static system seems to follow the factory drawing that I have showing both the pitot and static lines running up the left door post and into the nose of the left wing root rib. The static line just terminates at the first rib and the pitot continues out through rubber grommets in the nose ribs the the jury strut where the tubing connects with the pitot tube on the front jury strut.

My question concerns the tubing used for the pitot and static lines. The existing lines seem to be soft copper tubing with rubber tubing pieces held tight with wire ties serving as connectors between tubing pieces. The tubing is 0.190" outside diameter and about 0.085" internal diameter. My question is: What type of tubing was used on the original BC12-D? Is the soft copper original? What would be the best (approved!) tubing to be used today?

Any comments or suggestions are welcome, and any reference to real approved data will be met with shouts of glee!

Thanks loads in advance.
Skip Egdorf
TF #895
BC12D-4-85 N34237

[Hank Jarrett]

Re: Static System tubing information

Sounds (and looks) like what was in my 45 wings. I didn't like it much as the rubber was pretty bad and the wire twists didn't look like a very good way to do things. It is one of those things I would NOT be adverse to changing to a more modern materials (and I am a real originality nut). I think the soft copper was probably all right, but that rubber tube didn't look all that great.
Hank

I will be watching for ideas on better legal solutions.

[LostnSpace]

Re: Static System tubing information

Several years ago when I opened the left wing, the tubing was soft copper, but the static tube went out about another rib or 2, then was flattened on the end and had about 6 #40 holes drilled in it, i replaced it with soft aluminum, but used vinyl tube in place of the rubber connectores, wish you the best on your recover, gary

[Hank Jarrett]

Re: Static System tubing information

If I remember right Josh's plane had soft aluminum tube for the pressure line and my 41 has tube that looked just like the white plastic tube used for ice makers in a refrigerator. I asked at a local instrument shop and they told me that it was, in fact, the same tube and the nice thing is there is compression fitting hardware and adapters to attach the plastic tube to the threads on the back of the instruments.
Does anyone know if the plastic tube is accepted by the Feds? From what I have recently seen a WHOLE LOT of modern planes are using it.
Hank

I also found that all three of my planes had NO static line to the wing. All of the instruments needing static source were simply open behind the panel, which explains why some of the instruments jump when you open the windows. ;-)
I can't imagine the inside of the wing being a great place for taking static. Not bad, but not the best. Just a bit more stable than the cockpit.

[M Towsley]

Re: Static System tubing information

I finally blew out my static line, as my instruments were open to the back of the panel. It did help greatly on accuracy. I cannot get in, even with a video stick, to see how the static line was terminated.

[dalijohn]

Re: Static System tubing information

Years ago when I work for a major manufacturer on the large unpressurized cabin class airframes, we used a polyethene tubing, .250 dia x .040 thick for the static lines. I can check my old notebooks for additional info.