Thread: New Sight Tubes

I had the fuel sight tubes replaced at my last annual, about 2 months ago. They are now almost completely opaque. They were purchased from FD USA. I'd advise anyone contemplating replacing the sight tubes in their aircraft to wait until I get this sorted out.

I just got mine replaced and they were almost opaque to begin with. It was very difficult to see the fuel level.

Could you do me a favor and call Arian or Tom P. at Flight Design and let them know about it. Arian had never heard of the problem and seemed skeptical. Phone number is 860-963-7272.

We had ours replaced a month or two ago, and they are as clear as can be. Chesapeake Aviation, Chesapeake, VA - Bob Chandler.

it took 3 years for mine to go opaque. in this last year my new tubes have remained quite clear. I now wait till I am going flying to get fuel, if the fuel is near empty when sitting in the hangar, the tubes might last longer.

remember to replace any time you pull the wings.

same with motor mounts, if you are getting a firewall blanket change your rubber mounts if they are deteriorating.

I do know there was a change in the hose material being supplied from Flight Design USA. The new hose is harder to get pushed on the nipples, but less prone to kinking. The last one I did had the new hose. Tom

Ed, there's something different about the new tubes. I had the old tubes for 3 years as well. They gradually darkened, but you could still see sharply the fuel level if you looked close. The new tubes have turned milky white and it's very hard to see the level, even looking closely, after 2 months. Same gas, same hanger, same fuel level. The only thing that changed is the tube material. Whatever the material is, I also don't like the idea of it leaching into my fuel. I'm expecting a call back from FD soon. I hope.

Opaque is usually the result of solvent action. PVC/polyurethane tubing is my guess what they specify since it is reasonably fuel inert and it is stiffer than tygon type stuff but it is susceptible to aromatic solvents and such. DO you use a TEL scaveneger with 100LL? That would be the most likely culprit

IIRC i was once told to just get some new polyurethane tubing and add my own marks. perhaps we are going to a "new" tubing for no good reason?

Only Nylon and PU tubing are appropriate here for clear fuel line but the PU, while stiffer for same wall thickness, is MUCH more impacted by organic solvents, the kind in lead scavengers and in high end auto fuel where it is referred to as detergent. I'm concerned that is the new tubing. It's a bad choice.