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gascolator location

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grubac

Member
Hey Guys, quick question

Everyone tells me that it's critical to have your gascolator located at the lowest point in your aircraft's fuel system. Can anyone tell me why?
I mean, I understand that water and crud in your fuel tends to build up at the lowest point, but any water that builds up with the aircraft is grounded, will eventually run through the gascolator once the engine is started up again, meaning it'll be seperated. Does anyone disagree?

Any thoughts would be much appreciated.

Grubac
 
It can never really be the lowest point in the fuel system because of the wings. But, if you are going to have one, it should be the lowest point when compared to the engine, fuel pump, selector, ect.

The reason is that during static times, as you mentioned, water can make its way to the gascolator and pool there. At every pre-flight you remove any water collected, because the thing to remember is if the gascolator bowl is full of water it will no longer seperate it.
 
Hey Wade

Thanks for your reply. I see what you're saying. Basically if I empty the gascolator during my preflight check there could still be some water in the system that has built up around the lowest point in the sytem while the aircraft was grounded.

The thing is, the water that has built up at the lowest point will eventually be run through and collected by the gascolator once the booster pump is turned on and the engine is started. That being said, I guess the only negative aspect here is that you start flying with some water already in the gascolator, meaning there's a greater chance of it filling while in flight and allowing water to bypass it and flow directly into the engine.

But what are the chances of that happening? Has anyone ever had their gascolator fill up with water during one flight? Sounds a little unlikely, but then again, what do I know.

Grubac
 
If you do, you had to have leaky fuel cap o-rings during a rain shower. Always top your tanks whenever possible to help prevent condensation.
 
You also have wing sumps. Use them.

If outside and rain is possible, tape over the fuel caps. Make sure the cap O-ring is good.

Not an issue if you maintain the plane, take precautions and use the wing sumps and gascolator drain as required.
 
Not needed

At the risk of starting a war...............Gascolators are not needed in an RV. Yes I know that many have put them in, and they will at least work as a poor fuel filter, but they will also act as a heat sink in our tightly cowled aircraft. The low point in the fuel system is at the tank drains, and if you drain some fuel from them as part of your preflight you will drain any water in the tanks.

The Grumman series of certified aircraft do not have gascolators for the same reason. I'm not sure why Van even offers them other than grandfather worship. He probably got tired of explaining that they are not needed, and just left it up to the builder.

Over twelve years ago I decided it was not necessary and did not install one. After over eleven years of flying and nearly 1300 hours I'm happy with that decision.
 
gascolator

It isn't a heat sink if you "copy" Eustace Bowhay(sp?) builder of the 1st RV on floats and put it in the wing root like I did. On rare occausions I''ll get something out of it. It has worked well.

Danny King said:
At the risk of starting a war...............Gascolators are not needed in an RV. Yes I know that many have put them in, and they will at least work as a poor fuel filter, but they will also act as a heat sink in our tightly cowled aircraft. The low point in the fuel system is at the tank drains, and if you drain some fuel from them as part of your preflight you will drain any water in the tanks.

The Grumman series of certified aircraft do not have gascolators for the same reason. I'm not sure why Van even offers them other than grandfather worship. He probably got tired of explaining that they are not needed, and just left it up to the builder.

Over twelve years ago I decided it was not necessary and did not install one. After over eleven years of flying and nearly 1300 hours I'm happy with that decision.
Click to expand...
 
When we put temp probes on an RV12 that was having vapor lock problems, we found the hottest part of the engine compartment by far was - the gascolator! By building a shroud around it with a blast tube for cool air, it became a cooler part.
 
grubac said:
...any water that builds up with the aircraft is grounded, will eventually run through the gascolator once the engine is started up again, meaning it'll be seperated.
Click to expand...

FWIW, your question seems reasonable, except that I would expect that the collection efficiency of the gascolator would only be suitable when the airplane and fuel system are static. Once you move the airplane and suck/pump fuel through the system, I expect that any water and crud might be dispersed and swept through the system before it could settle into the bowl. Make sense?

Rob
 
Rob Erdos said:
FWIW, your question seems reasonable, except that I would expect that the collection efficiency of the gascolator would only be suitable when the airplane and fuel system are static. Once you move the airplane and suck/pump fuel through the system, I expect that any water and crud might be dispersed and swept through the system before it could settle into the bowl. Make sense?

Rob
Click to expand...

On any gascolator I've ever seen the inlet is a standpipe almost to the bottom of the bowl, and the outlet is through a screen the diameter of the bowl (less standpipe through-hole) at the top. The screen is fine enough that it passes fuel preferentially to water (higher surface tension than fuel), so you'd have to push a BUNCH of water and crud through the system to overwhelm it.
 
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