The factory supplied sight gauge tubing is polyurethane (see Chpt 30). We
noticed
it was getting hard to read because of yellowing and also very hard and brittle
after about 2 years exposure to auto gas. Decided to replace it during
our after ground loop rebuild.
Went to the Tygon web site (www.tygon.com) to find alternatives. F4040A is
listed as fuel tubing. However Europa supplied a length of that with our Long
Range tank. The F4040A was inside the main tank and exposed to gasoline.
After about 2 years it not only was virtually opague but it was hard and
brittle. Decided against F4040A.
Tygon Tech rep suggested Tygothane C210A or Tygon SE200. Tygothane C210A is
polyurethane
without plasticizers. It should hold up to gasoline well. SE200 is
PVC with a teflon liner. A search of literature suggests teflon is one of the
most gasoline resistant materials.
We cut short sections of F4040A, SE200 and C210A filled them with auto gas and
plugged both ends. The gas eventually leaked out of all of them, but it was out
of the F4040A in a day or two, C210A about a month and SE200 took 3 months.
We also put short pieces in a jar of auto gas. F4040A has discolored and gotten
much stiffer in 3 months. C210A is discolored but not stiffer and SE200
the PVC has shrunk but the teflon liner has not changed.
So we are using SE200 for our sight gauge. For the Long Range tank feed, we
used
C210A. We also measure fuel quantity with a pressure sensor similar to Tony
K's system feeding an input to our GRT EIS and the EIS calculates fuel usage
---From flow transducers.
Attached is a photo of the sight gauge up the back of the cockpit module.
Jim & Heather Butcher
N241BW
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