Fuel Question

[Maurus]

When I sump the left wing of my father's aircraft, It comes out as a pretty dark blue, I can sump it enough to get the normal light blue fuel,but it seems that it happens every time. What could be causing this?

 

[CoffeeIcePapers]

When I sump the left wing of my father's aircraft, It comes out as a pretty dark blue, I can sump it enough to get the normal light blue fuel,but it seems that it happens every time. What could be causing this?

Maybe the dye in the fuel is concentrating at the bottom of the wings. Did it sit for a long time recently?

 

[Maurus]

About a month, weather in Ohio is terrible, especially when mixed with class finals and papers. Thing is that it only does it in the one wing. Kinda weird

 

[Cessnaflyer]

Is that one wing positioned where more of the fuel can be concentrated over the sump? Also is it a bladder where a wrinkle on the opposite wing could be posing a problem with the same settling problem?

 

[Stoneage]

My guess is that the fuel sump drain has the slightest leak and the fuel is evaporating as it leaks (without dripping). Fuel can evaporate but the dye can't so it becomes concentrated and you get this tiny bit of concentrated dye when you take a sample.
To test this idea take a very small sample, check its color, discard and take another small sample and check its color. If my guess is correct the second sample will be much lighter and a third sample will be about the same as the other wing.

-- StoneAge

 

[Maurus]

Yes it does clear up with the more samples I take. sounds like that could be the problem, now I just need to know how fast it is leaking, can't be too fast. Even if it is slow, a slow leak will cause a lot of lost fuel over time.


Might help to know that we are working with a Piper Arrow II (PA-28R-200)

 

[Minuteman]

Your airplane could have yeast infection.

Avgas is sterile when first produced because of the high refinery processing temperatures. But it becomes contaminated with microorganisms that are always present in air and water. These include bacteria and fungi (yeasts and molds). The solids formed by biogrowth are very effective at plugging fuel filters. Some microorganisms also generate acidic by-products that can accelerate metal corrosion.

Since most microorganisms need free water to grow, biogrowth is usually concentrated at the fuel-water interface, when one exists. Some organisms need air to grow (aerobic organisms), while others grow only in the absence of air (anaerobic organisms). In addition to food (fuel) and water, microorganisms also need certain elemental nutrients. Phosphorus is the only one whose concentration might be low enough to limit biogrowth. Higher ambient temperatures also favor biogrowth.

Microbial contamination of avgas is less common than in other petroleum products, presumably due to the toxicity of tetraethyl lead, but it does occur. The best approach to microbial contamination is prevention. And the most important preventive step is keeping the amount of water in the fuel storage tank as low as possible. No additives are approved as biocides in the major avgas specifications.

http://www.chevron.com/products/prodserv/fuels/bulletin/aviationfuel/8_ag_perf.shtm

 

[Stoneage]

Unless it is dripping, and if it were then the dye would not get concentrated and make the fuel samples dark blue, it is not a concern. Make a mental note to be especially aware to monitor that sump drain for problems. It could be a small particle on the seat of the sump drain that is allowing a tiny amount of fuel to escape. Or it could be a problem about to get worse. Nothing to be worried about just keep an eye on it.

-- StoneAge