[JimWoo50]

I have read various postings on the pros and cons of a gascolator and I am seriously thinking of omitting it. I can check for water through the wing drains and my fuel pickups have screens on them. It just seems like more of a hassle and extra weight than its worth. Besides I have owned a 172 for a long time and have never found anything in the bowl which leads me to believe that it is unnecessary. Opinions anyone?

 

[OneTwoSierra]

Just finished my first annual and had a a film/wad of lint in mine. I think they're a net plus, but others have omitted with no problem.

 

[Captain_John]

Brian, what was the lint and where did it come from? Also, what are you running for fuel filters?

I too am considering omitting the gascolator and was wondering if so, what filters to use in place of them.

Anyone???

CJ

 

[sf3543]

My last planes, a Grumman TR2, RV6 and now RV8 did not have gascolators. I have never had a problem in about 1500 hours among them.
There are lots of opinions on whether or not you need one, but in my opinion, if you can't install it in a low point in the fuel system, where water would naturally settle in, they don't really provide anything except another failure point. If you have to have a filter, then put one in line, but even then, I have heard of several people who have had clogged or burst filters, causing additional problems. (I think the filter media was probably too fine in the clogged filter scenario.) On my fuel injected installation, I have a fuel filter placed just prior to the pump, so fuel gets filtered from both tanks. This is VAN's basic set up for FI set ups.
Install a gascolator if you feel you need to, or a filter if you want, but I would recommend that you stick with the recommendations from proven fuel systems. This is one place where I would not want to experiment.

 

[gmcjetpilot]

The winner is

I have read various postings on the pros and cons of a gascolator and I am seriously thinking of omitting it. Opinions anyone?

I vote for following the plans (I know call me crazy).

I have heard it all and think the firewall gascolator provides the largest catch basin for water and best chance to save the day, IF the day would ever need saving. The TRUTH is if no water or other contaminates are introduced into the fuel system than you don't need a filter of any kind.

The down side with just in-line filters is the volume of the SUMP or ability to hold larger amounts of water.

SO the winner is.... (drum roll)...... envelope please............ my opinion is the good old big fat gascolator on the fire wall provides the most ROBUST system for some serious contamination problem.

It is also STANDARD, common, universal, known, conventional, tried and true, blaaa blaaa blaaa. However all this conformity has MANY benefits. Any pilot will know how to pre-flight it. Almost every Piper and Cessna I flew has a FW gas bucket gunk catcher.

If you ever sell it and the airplane has a fuel related crash and you did not follow the "common wisdom" of the ages than you might open up a small liability door. Hey, you are not paranoid if they really are out to get you.

As you said you are going to check / sump the tanks every time, check the fuel caps don't leak, keep it out of the rain, assure good fuel it uploaded and so on. Hey it is experimental do what floats your boat. What are you saving? Cost, Weight, more better...

I played around with idea of deleting the gascolator with small gascolator's / sump's in the wing root, in-line filters and so on. I decided.........(drum roll)....... to go with the good OLD method of protecting the fuel supply, from water and other contaminates, the gascolator. I know, it's boring. I know it works. That is the best argument if you will.

I am opinionated and think the creativity should be left to your panel layout and paint scheme. Major systems like fuel should be kept simple and per plans.

Also consider maintenance of these in-line hidden filters. The firewall gascolator is there to see, touch and smell, not out of sight, out of mind.

IF YOU TAKE ON A ONE OF A KIND UNIQUE FUEL SYSTEM OF YOU OWN DESIGN, YOU BETTER KNOW WHAT YOU ARE DOING, TEST IT AND THINK OF EVERYTHING THAT MIGHT GO WRONG WITH IT, BECAUSE IT JUST MIGHT. (I am not saying the FW GAS-CO is perfect, nothing is, but we know what we are dealing with.)

Serioulsy there are some rules of fuel system design you may want to research. I recall one is filters should need be course at first, and the fine filter'(s) are located down stream or last. Also the plane is ground tested by placing it in an extream climb attitude (which is hard to do since RV's climb steeply) and max flow rate is varified. I am no expert, but that is why I follow the plans.

That is why one BIG centrally located gascolator has stood the test of time, simple, robust and sized for the application. Start messing with small filters and small remote gascolators, you might be hurting your self? If you are smarter than do your thing.

The above are my opinions and do not necessarily express the views of this station, management or it's affiliates. I don't care what anyone else does BTW, and I try not to convince anyone, just stating my rational.

 

[rv8ch]

Gascolator

I have read various postings on the pros and cons of a gascolator and I am seriously thinking of omitting it. I can check for water through the wing drains and my fuel pickups have screens on them. It just seems like more of a hassle and extra weight than its worth. ... Opinions anyone?

Opinions are easily found here, that's for sure!

You didn't mention if you are installing fuel injection or a carburator.

If you are building a tail dragger, the low point of the system will be your wing tanks, that's for sure.

Some (all?) FI suppliers do not recommend a gascolator. I'd check with them to get their opinion.

Here's a great article on fuel systems: http://www.rv8.ch/staticpages/index.php/20030914230507849

 

[gmcjetpilot]

Logic of the gascolator

If you are building a tail dragger, the low point of the system will be your wing tanks, that's for sure.

I don't think it matters if it's tail dragger or not. The wing tank sumps tend to be the low spot regardless.

Here is the logic:

Clearly for pref-light the wing tanks are where water will most likely enter after you park it. However the gascolator check is basically from the last time you flew it. It is not likely water will get into the gascolator parked, unless fuel is running thru the system. Make sense?

It is about the things and stuff that gets caught AFTER it gets sucked out the tank. In a climb or descent the gascolator is high or low relative to the wing. The gascolator is just a large filter and a place to hold water.

This logic above is what makes the gascolator on the firewall, fairly close to the engine idea. It does not have to be the absolute bottom of the fuel system but close is good enough.

Also size does matter. A large bowl with some height allows water and sediment room to settle before trying to pass a screen or filter element. A little round in-line aluminum billet filter laying on its side may look cool but has little room to collect water or sediment.

 

[Captain_John]

According to Ken on Page 220 of the RVATOR, the gasco SHOULD be at the low point in the system and he goes on to say that this is difficult in a taildragger.

Also he hgoes on to say that vapor lock can be a problem as well. I am gleaning that this stems from the fact that we have tightly cowled ships and Ken says that a cooling tube leading to it should be considered.

I am still on the fence about this one.

Now, what about ceramic element filters? Should we use them in lieu of paper ones? You know, like the ones sold at hot rod shops...

CJ

 

[rv8ch]

filters

Now, what about ceramic element filters? Should we use them in lieu of paper ones? You know, like the ones sold at hot rod shops...

I've never heard of ceramic filters. Do you have any pointers? I'm using a stainless steel 100 micron Aeromotive pre-filter, and a 10 micron cellulose (paper) filter after the fuel pumps. If I were doing it again, I'd look at the flowezy filters. http://www.FlowEzyFilters.com/

 

[Dgamble]

I just had what must be the six or seventh condition inspection on this airplane and found a small piece of aluminum caught in the gascolator filter, probably left over from the build.

I suppose it would have been caught at the final fuel filter too, but my GasCo is located such that it is far easier to get to, and has a more generously sized filter which would presumably be more resistant to blocking the fuel flow in the event of catching a relatively large piece of debris.

 

[Captain_John]

I was thinkin' one of these filters. I thought they had ceramic interiors, but I may be wrong.

They come sized in AN6 with a really cool bracket!

...or this cool see through glass one makes me all warm and fuzzy too!

Whatcha think? I suppose?

CJ

 

[Yukon]

More car parts!

I was thinkin' one of these filters. I thought they had ceramic interiors, but I may be wrong.

They come sized in AN6 with a really cool bracket!

Whatcha think? I suppose?

CJ

I think these are car parts!

 

[Captain_John]

Hahaha, they are car parts! They look ALMOST like airplane parts!

Your alternator is a car part! Probably your belt is too!

CJ

 

[fodrv7]

Apples and oranges

Slight difference between a failed alternator and a failed fuel system.

It's not that car parts aren't good enough, it's that you DON'T KNOW if they are good enough.
Pete.

 

[Captain_John]

Slight difference between a failed alternator and a failed fuel system.

It's not that car parts aren't good enough, it's that you DON'T KNOW if they are good enough.
Pete.

True enough... I just wanted to put it up here for food for thought.

I am considering buying three. One for my boat and testing it for the next few years. The marine environment is more demanding but not as consequential.

I am at least a couple of years away from FF stuff, but I like to look ahead.

CJ

 

[fodrv7]

Racor

One for my boat and testing it for the next few years. The marine environment is more demanding but not as consequential.

CJ,
I had a pair of RACOR filters on my 46' Nordhavn.
HUGE.
The glass bowl held about a quart. They had suction gauges to indicate filter blocking and an electical sensor to indicate the presents of water.
Wish I had one on my RV.
Pete

 

[Captain_John]

Exactly, I mean... what IS an experimental airplane part anyways?

Case in point, the Dynon displays, LED Nav lights, Many brands of wooden props, Vans Engine mounts, Andair valves etc...

None of these things have ever been PMA'ed and likely never will.

It is up to we, the builders to deem it airworthy.

Regarding the filters, a pair would be wisest I think. If one malfunctioned there would still be the other.

CJ

 

[fodrv7]

Two of.

Somebody put one on each side in the wing root under the intersection fairing. It seems to solve lot of the issues raised.

Apparently down stream of a FI boost pump won't work as the water is too mixed with the fuel to settle out in the gascolator bowl.
Pete.

 

[OneTwoSierra]

Brian, what was the lint and where did it come from? Also, what are you running for fuel filters?

I too am considering omitting the gascolator and was wondering if so, what filters to use in place of them.

Anyone???

CJ

It was just a collection of tiny little lint pieces. There's no other way to describe it. No, I have no other filter except screens on the pick up tubes (if you call those a filter). I'm guessing the link was just a collection of tiny fuzz particles from the filters of the pumps where I get gas.

As a side note, I had nothing in the gascolator after 50 hours, but found this after 115. Could have been just one tank of gas (I get it all over depending on where I am). The tiny screen in the colator is the best. I think the bowl like design of the colator is ideal, letting particles (and water) settle so as not to clog.

 

[gmcjetpilot]

It's getting hot in here

According to Ken on Page 220 of the RVATOR, the gasco SHOULD be at the low point in the system and he goes on to say that this is difficult in a taildragger.

Also he goes on to say that vapor lock can be a problem as well. I am gleaning that this stems from the fact that we have tightly cowled ships and Ken says that a cooling tube leading to it should be considered.

I was thinkin' one of these filters. I thought they had ceramic interiors, but I may be wrong.

They come sized in AN6 with a really cool bracket! ...or this cool see through glass one makes me all warm and fuzzy too!

What is page 220? I know Ken and the RVator. Is that in the 20 year compilation of RVators?

Look in flight the gascolator, taildragger or Trike, is basically at the same level on the firewall, so I don't get the significance. The gascolator is for in-flight, not when parked and the engine is not running. Right?

You will not save much by adding multiple drain points or in-line filters. I would stay away from automotive products. Again FUEL SYSTEM IS MUCHO CRITICAL!

In fact one NTSB report discussed a automotive/racing oil filter housing used in a plane that failed. The casting cracked.

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20051024X01711&key=1

There have been "aircraft" gascolator problems but at least there is safety in numbers. You are more likely to know if a problem is reported with a gascolator sold for aircraft use. Like Vans service letter.

http://www.vansaircraft.com/pdf/gascolator.pdf

The point is use aircraft stuff if for not other reason everyone else is using it successfully.

As far as heat soaked as a reason for NOT using the firewall location, I think is not critical. I dis-agree with Ken, vapor lock, is not where it happens.

If you use Aviation or Avfuel you have nothing to worry about, but with auto fuel all bets are off. ***


*** If you plan on autogas which is more subject to vapor lock than AVgas, yes I would do all I could to shield the fuel from heat, including the gascolator. Put a box and air blast tube. However to be honest more heat is imparted to the fuel from the mechanical fuel pump and carb itself than the gascolator. There are fuel pump shields for use with air blast tubes as well.

Many single engine Piper's, they made a little box for the electric Aux fuel pump and gascolator mounted on the firewall to shield it from heat.

A search of NTSB accident/incident reports with "automotive fuel", I found 250 hits, 50 in experimental aircraft. I took a quick look at a sample of the reports. There was a clear correlation to unexplained power loss, high ambient temps and auto fuel, presumably from vapor lock. Again the gascolator may add a little heat to the fuel, but when gasoline overheats and boils it is inside the carburetor bowl or fuel pump of a hot engine, when it ceases to flow. It can boil in hoses and lines but assume those are insulated.

Even a Piper Cherokee 180 had power loss and forced landing from cruise.
http://www.ntsb.gov/ntsb/GenPDF.asp?id=IAD05LA103&rpt=fi

There where many, at least 15 experimentals that suffered power loss on takeoff or cruise in hot temps. You can search the NTSB reports yourself.

The point is if you have auto fuel you can't get too paranoid about vapor lock in a tightly cowl RV with auto fuel. I know many use MOgas in their Rotary and Subaru powered RV. Those are a different animal with no mechanical fuel pumps. I am addressing Lyc fuel systems.

 

[RV8RIVETER]

What is the real issue?

I have a FI IO-360 angle valve. I have been personally debating the gascolator issue, since I am about to start plumbing. So, in the context of FI...

I am afraid as of this moment, I do not see the reason to have a gascolator. Have I missed something? I have an open mind, so if someone has a HARD theoretical or data driven reason to install one I would like to hear it. Don't care about "it is for airplanes" or " I have always used one so..".

As for fuel filters, avgas is not much different from mogas when it comes to filters, so since the filter doesn't know any better why not use one as long as it is robust and well made. I personally would be hesitant put one on the pressure side of the pump since Lyc FI runs higher pressure than a std auto. I have the Airflow performance pump and filter kit from Van's and I plan on installing the individual pre-filters on each tank at the wing root. If something gets past those two filters, I don't see it being caught in the gascolator, unless it is water or the pump started coming apart. How big an issue have poeple with gascolators had with water in them? I have not talked with anyone who has found more than a 1/2 thimble full.

Ready to hear more.

 

[Steve Sampson]

Rethinking Gascolators - another approach

I am building an RV4 and have been mulling over what to do about gascolators and for a variety of reasons have decided (almost) to keep it but move it off the firewall, just after the fuel valve inside the cabin.

The reasons to do this are:

1. The fuel wont get cooked
2. The firewall is tight - this simplifies things
3. The fuel will get filtered before it goes through the Floscan
4. The fuel will get filtered for crud though I expect the wing drains to manage the water.

The negatives are:

1) It is relatively hard to get to, though not difficult. However I will not plan on checking it each flight - only the wing drains. I will treat it like a filter on an injected engine which would be located in a similar location, and not checked every flight.
2) I will use an Andair since it is relatively easy to disassemble.
3) Some have said smell? I dont see why it should leak anymore than the rest of the hardware.

My reasion for posting is that I would like to get some comments regarding this approach in case there is an issue I have not thought of.

Thanks!

 

[Captain_John]

George, buy the new book.

The guy with the auto fuel filter problem is in the new book in that same article that Ken wrote.

Q. Are there any aviation grade filters?

I am still open to a gasco, don't get me wrong. I just want to give all this stuff due diligence.

CJ

 

[ptrotter]

I'm sure this will evoke some comments, but I am considering 2 Andair gascolators, one in each wing root. It is not so much that I believe a gascolator is necessary, but I wanted filters in each wing root to eliminate the possibility of a single filter clog causing an engine failure. There are several filter choices available, but the Andair gascolator provides good filtering in a simple to remove and clean housing. They would be mounted so that the drain extends through the bottom of the wing root fairing. This is fairly low but probably not quite at the lowest point of the fuel system.

 

[azrv6]

I have an RV-6 and can comment that depending upon the fuel level in the tanks, if you disconnect a component in the fuel system between the tank and the fuel shut off valve, you may have gas flowing. The first time I lubed the fuel shut off valve I had no problems because the fuel level in the tanks was low. The next time I went to lube the valve, fuel started flowing when I removed the valve. Of course, the tanks were pretty full. So, I don't know how the fuel lines are routed in other RV models, but if you are considering in-line filters before the fuel shut off valve or gascolators at a low point in the wing root, there might be an added complication with performing maintenance during annual condition inspections - the need to make sure the tanks are below a certain level depending on where you put things.

BTW, I have an O-360, carb, simple old style gascolator on the firewall, simple blast tube from the baffling. 500 hrs in the southwest, 150 hours in Az and no vapor lock problems.

 

[gmcjetpilot]

got flow?

I'm sure this will evoke some comments, but I am considering 2 Andair gascolators, one in each wing root.

When I was considering those little gascolators myself, I saw that the rated flow rate was too little for a our engines? Just a thought. There are three size's and the part #'s are GAS 125, 370 and 500. I think the number means the HP of engine that it is suited for? Not sure check it out. The 370 is the larger one that fits on the firewall. I don't think that will fit in the wing root.

 

[jonbakerok]

Airplanes have gascolators

The reason airplanes have gascolators instead of fuel filters is that a gascolator can't get blocked and it can catch water as well as dirt.

I've had lots of instances of blocked fuel filters in cars over the years. I don't know why anyone would want to risk that in an airplane.

Here's a story that illustrates why you need something in your fuel system that can catch water:

Last year a friend and I flew up to Osh in my RV, loaded to the gills with camping equipment. One night while we were there, it stormed so bad it just about blew our tent away. The day we left, I carefully sumped the tanks, but didn't find any water. The plane flew fine -- no problems, 900 miles back to Houston.

Next flight, I sumped the tanks and got nearly a full measure of water out of each tank. That caused me to check the gascolator (which I hardly ever do) -- it was nearly full of water.

The reason I didn't see water when I sumped it at Osh was that it was loaded so heavy that the tail was low and the water had settled to the back of the tank (wouldn't that always be the case with a taildragger?). During the flight home, some of that water sloshed to the drain, but thank heavens, it was trapped in the Gascolator, so the Lyc never even hiccupped.

That's why airplanes have gascolators instead of fuel filters.

 

[aadamson]

Andair GS's

When I was considering those little gascolators myself, I saw that the rated flow rate was too little for a our engines? Just a thought. There are three size's and the part #'s are GAS 125, 370 and 500. I think the number means the HP of engine that it is suited for? Not sure check it out. The 370 is the larger one that fits on the firewall. I don't think that will fit in the wing root.

Pretty sure the number is the "cubes" of engine. For example, the Lancair Legacy comes with a gascolator from Andair. If you build the one that takes the 4 cyl, you use the 300 series, if you build one that can take the 6 cyl (500ish cubes), you use the 500 series. I suspect the 125 is for the little Rotax engines, but that's just a guess, the other 2 I know. The 300 and the 500 are both FW mounted perferred units.

 

[ptrotter]

The Andair part numbers refer to the fitting size on the gascolators, 125, 375 and 500 refer to 1/4", 3/8" and 1/2" fitting respectively. The 375 is the appropriate unit for RVs. It is capable of at least 50-60 gallons per hour fuel flow and is the unit that Vans sells.

This info came directly form Andy Phillips at Andair, so it is accurate.

 

[gmcjetpilot]

Its the size

The Andair part numbers refer to the fitting size on the gascolators, 125, 375 and 500 refer to 1/4", 3/8" and 1/2" fitting respectively. This info came directly form Andy Phillips at Andair, so it is accurate.

I knew the numbers meant something. 375 for .375" and 500 for .500" ? Not sure where 125 came from.

Or is it cubic inches as Alan said?

From the Ad I have, it seems the GAS-125 is for 140 HP and the GAS-500 is for 500 HP; that's what is mentioned in the advertised description?


He is from England so it could be fortnights per furlongs?


Any way it does not matter 1/4", 125 cu-in or 140 HP, part # GAS-125 is too small (low flow) for most RV's.


As far as heat, cooking the gascolator and fuel, that's a legit worry. Just shield it from the exhaust pipes. Better yet, ceramic coat the exhaust, in and out. Add a shield box and blast tube and it will be plenty cool.

The real gasoline cooker and heat is from the mechanical fuel pump. I wounder if that is why Lycoming moved the fuel pup front left on some engines like the 320-H2AD and 540's? By the way here is a cool shield / shroud and blast tube for the mechanical fuel pump ($65).

http://www.showplanes.com/index_1024.htm click products and fuel pump shroud

 

[Captain_John]

The reason airplanes have gascolators instead of fuel filters is that a gascolator can't get blocked and it can catch water as well as dirt.

I've had lots of instances of blocked fuel filters in cars over the years. I don't know why anyone would want to risk that in an airplane.

Here's a story that illustrates why you need something in your fuel system that can catch water:

Last year a friend and I flew up to Osh in my RV, loaded to the gills with camping equipment. One night while we were there, it stormed so bad it just about blew our tent away. The day we left, I carefully sumped the tanks, but didn't find any water. The plane flew fine -- no problems, 900 miles back to Houston.

Next flight, I sumped the tanks and got nearly a full measure of water out of each tank. That caused me to check the gascolator (which I hardly ever do) -- it was nearly full of water.

The reason I didn't see water when I sumped it at Osh was that it was loaded so heavy that the tail was low and the water had settled to the back of the tank (wouldn't that always be the case with a taildragger?). During the flight home, some of that water sloshed to the drain, but thank heavens, it was trapped in the Gascolator, so the Lyc never even hiccupped.

That's why airplanes have gascolators instead of fuel filters.

John, Thanks for the story! Looks like it'll be gasco's for me!

Paul, two of 'em...huh? I kinda like that! One at each wing root. Sounds nice an cool there! Have you installed them yet?

CJ

 

[Yukon]

Gasolator for me

Good job, Captain!

 

[gmcjetpilot]

Great idea almost there

John, Thanks for the story! Looks like it'll be gasco's for me! Paul, two of 'em...huh? I kinda like that! One at each wing root. Sounds nice an cool there! Have you installed them yet? CJ

That was to topic about the Andair gascolators. The GAS-375 is the standard one (firewall), but it's to big to stuff into the gap between wing root and fuselage. The Andair gascolator model GAS-125 is a small thing. It is either listed for up to 140 HP and only 1/4" fittings. Also being small they hold much less water. Also why have TWO gascolators to lean down and drain.

Per jonbakerok, you see the gascolator does did not have water in the gascolator until after the flight. Draining the gascolator is for the PREVIOUS flight, so the absolute lowest point for the gascolator is important but not critical. You want it at least below the Carb if you have one. Here are pictures of what other builders have done.

click me


If using solid tube, I would fire sleeve it, why not?


Interesting little bracket on bottom. Notice air-blast tube (black corrugated). I would add an exhaust heat shield.


This shows a RIGHT side mounted gascolator but higher with a drain extension.
Although this is per plan's, I'm not crazy about having the gas & electrical all in one spot.


Last is another drain extension. I like the idea of not having to cantilever the gascolator to
clear the engine mount tube, I do prefer to get the gascolator lower. I doubt it makes much performance differnce.
The extension does seem to protect the gascolator. Also it is mounted far outboard, cooler, protected and out of the way.

 

[ptrotter]

My idea of Andair gascolators in the wing root is to use them as a filter that is easily cleaned. The water seperation aspect is simply a bonus, but I doubt if I can get them low enough to do that properly.

George, as far as I can tell, I should be able to get them in the root. My plan was to mount them on the fuselage. It may work, it may not. we'll see I'm pretty sure it has been done before and I think the RV-8 may have a little more room in the root than some of the other RVs.

 

[gmcjetpilot]

More money more weight?

George, as far as I can tell, I should be able to get them in the root.

Yea if you can get Two GAS-375 in the wing root, but the GAS-125 is too small in my opinion. You are talking about two expensive gascolator's. When faced with a decision I always look at keeping it simple, cost and weight, where safety is the overriding consideration. Of course the dual wing root gascolator is plenty safe, so if they can fit sure.

Keeping it "standard", is a good thing as I said, but dual wing root gascolator's sure sounds OK. However it heavier and more expensive to have two gascolators. I just don't see the gain over the single firewall gascolator.

I read the Pro's of NOT using a firewall gascolator, but I don't personally buy the reasons or at least put much weight on them. Gascolators can be cooled and there is room on the firewall. One gascolator is less expensive, lighter, simple and I think easier to drain. Just one man's opinion, either way is fine, but I am going with a single left firewall mounted Andair GAS-375.

On my old RV-4 I had a Cessna type with the handle you could pull through cowl oil door. The down side was you just pissed fuel on the ground (not green friendly) and you did not have a chance to observe what came out. I would not recommend doing this. The Andair is light and high quality. The one Van sells is OK as well.

 

[osxuser]

My arguement against the glass filters is:

When they fill with water, all they will help you with is timeing when your engine will quit...

A gascolator at least traps water away from the main fuel supply for a while. I personally like Cessna's gascolators and will be installing one in my -7. As for "one more failure point" me thinks having a gascolator & final filter would be the same as having a glass screen and a final filter...

 

[RV8RIVETER]

Water is all

Gascolater still does not seem needed on fuel injection.

As far as "clogging" filters. You obviously do not want a small filter, but something big enough to have adequate area to supply fuel when say 25-40% "clogged". If you have a AP FI electric fuel pump, you have a big filter just in front of it. Planning on large pre-filters in each wing root ( scheduled change items say after first 2 hrs and then every 6 months), to save the pump filter. Definetely seems too expensive to use gascolators for this purpose, but to each his own.

A gascolator on the firewall then only traps water and any large debris from an electric fuel pump "letting go". A disintegrating fuel pump would seem a very rare occurrence. Which leads me back to water and looks like only one poster had a case for water after a heavy overnight rainstorm .

 

[jonbakerok]

Which leads me back to water and looks like only one poster had a case for water after a heavy overnight rainstorm .

One incident in a three years of flying seems significant. But I guess you could just make sure your plane is never in its entire lifetime exposed to rain.

Anybody know why gascolators are currently out of fashion? I don't get that.

As far as the wing root idea, I'm with George. Why go to all that trouble to hang a couple of very expensive toy gascolators there? There must be a misconception about how these things work. It's not just a bowl at the bottom of the system. It's a centrifuge. And two little ones do not equal one big one -- you only use one tank at a time.

If you're worried about vapor lock, a Naca vent in the cowl would be a heck of a lot easier than all that extra plumbing. But has anyone ever reported gascolator-related vapor lock on an RV?

The fuel system is not a great place to exercise your "Experimental" tag.

 

[Yukon]

Got to Experiment!

"Anybody know why gascolators are currently out of fashion? I don't get that."
Jon,

I don't get it either! I'll gladly copy a proven fuel system anyday rather than subject my young *ss to unnecessary risk. I think alot of these guys have yet to experience the terror of an engine problem in a single engine airplane.

 

[Bob Axsom]

None in My Plane

I have four tanks that are individually selectable and a fuel filter in the line from each tank (yes 4 of them) and no gascolator. 223 hrs no problem. Make your own choice, this has been beat to death and I do not intend to dig through my records again for the filter numbers for this iteration of the brow wrinkling and hand wringing. It doesn't help and the argument will not go away.

I put about 4,200 hours on the Archer that I owned before building my RV-6A. I used for my daily commute to work in the Los Angeles area and travel all over the country and into Canada and deep into Mexico. All the gascolator gave me was damage to the cowl when the mechanic removed and install the cowl for maintenance.

Bob Axsom

 

[ptrotter]

I do not like the idea that a clogged fuel filter can shut down my engine as would be the case in the stadard configuration. Although this may be an unlikely occurrance, it is a possibility, and if I can reduce that possibility easily, I will. Therefore I feel that a filter on each tank is a good idea. Obviously these filters must be as good as would normally be used in the standard configuration.

There have been a couple of filters suggested for this purpose in the past which should be able to be found in the archives of the various lists. Using an Andair gascolator for this purpose is just an idea. These units are well built and have a good filter that is easy to remove and clean. The water seperation function could be an added bonus over a plain filter. And they are readily available. Of course you would need to use the proper one for the fuel flow. It is probably overkill for the application as I would still put in the normal filter at my FI pump location.

 

[RV8RIVETER]

Don't get it

Hey, I have nothing against gascolators or their use. I also don't believe in that is the way it was always done so why change.

In examining my choice, I was wondering why some felt it neccessary to filter 3-4 feet (pump/filter to engine distance) of fuel line? Second opinions are a great way to make sure one considers all aspects of a problem/decision. So, I am tankfull for all the input.

Risk calculation, I am afraid has a big "viewpoint" component, so whatever it takes to make you happy.

"Anybody know why gascolators are currently out of fashion? I don't get that."
Jon,

I don't get it either! I'll gladly copy a proven fuel system anyday rather than subject my young *ss to unnecessary risk. I think alot of these guys have yet to experience the terror of an engine problem in a single engine airplane.

 

[Yukon]

Proven Track Record

Wade,

Another way of saying "just because it's the way it's always been done" is "proven track record". Millions and millions of flight hours on gascolator systems in airplanes. I know filters work in cars, but they also plug up in cars and cause engines to quit. I've had several over the years.

Think about this. With a gascolator, you check the integrity of your fuel system before each flight. Not only do you see the evidence of debris in your filter, you clean most of it out by draining the sump. With daily sump draining, you also get early warning of a water problem, be it from bad cap orings, bad gas (contamination) or condensation. Sometimes the wing sumps won't catch what the gascolator will.

With paper element fuel filters, you get none of these advantages, except the labor you save from not installing the gascolator.

 

[rv8ch]

gascolator vs. filters

With daily sump draining, you also get early warning of a water problem, be it from bad cap orings, bad gas (contamination) or condensation. Sometimes the wing sumps won't catch what the gascolator will.

On an RV8 or other taildragger, aren't the wing sumps the low points, so won't any water collect there? Also, if you are running a FI engine, then blowing a bit of water into the engine from time to time should not cause much trouble, should it? Water could be more of a problem with a carb, though.

The only clue I've ever seen that a gascolator had junk it it was when the little drain valve refused to seat properly. If this happens with a high pressure FI system, it seems like you'll either leak a lot of fuel if the gascolator is on the high pressure side, or suck a lot of air if it's on the low pressure side. Either one is not good, and seems to be avoidable with a good quality in-line filter.

With paper element fuel filters, you get none of these advantages, except the labor you save from not installing the gascolator.

Good quality in-line filters should stop all the gunk and should not clog up unless you have a serious problem, like fuel lines rotting on the inside. The tank strainer should stop any decent sized bits of debris, like chunks of proseal.

Here's how I've done my fuel system with dual electric fuel pumps, dual 100 micron stainless steel pre-filters, and dual 10 micron paper element high pressure filters:

 

[ptrotter]

Mickey,

That looks good, but I would have put the fuel filters before the fuel selector valve. I guess there are pros and cons to each method.

 

[G-force]

I dont know the specifics for aviation fuel injections systems...but in the Marine industry, we always filter at 100 microns with a a stainless steel elemental filter, then a water seperator, then the 10 micron filter after the fuel pump. Pump vanes wear and and can send debris into the injectors hence the 10 micron filter after the pump, right before the injectors. The tiny orifices in injectors are not tolerant to debris at all. One thing to note, is most 10 micron filters are paper or cellious...and they swell shut with water, hence the importance of a seperator before it and the pump. If I were designing and plumbing a FI system, some sort or water seperator would be of great importance.

Mike

 

[rv8ch]

fuel filters

...One thing to note, is most 10 micron filters are paper or cellious...and they swell shut with water, hence the importance of a seperator before it and the pump. If I were designing and plumbing a FI system, some sort or water seperator would be of great importance.

Good point. I've done a bit of testing on this issue.

http://www.rv8.ch/article.php?story=2005052420523369

I'm not yet sure I have a 100% perfect solution to the problem of water. Of course, I don't expect to get too much into the system. If you know of a 10 micron filter that does not clog with water, that would be great info!

 

[Kevin Horton]

On an RV8 or other taildragger, aren't the wing sumps the low points, so won't any water will collect there?[/IMG]

True, but it can take several hours for all the water to come out of suspension and settle to the bottom of the tank. There will be times when you fuel the aircraft, then don't fly for a long time, and sumping the tanks would find the water. There will be other times when you will fuel the aircraft and fly without waiting several hours. In this case, a gascolator would probably provide a larger reservoir to catch water than a filter would.

 

[Yukon]

Gascolater??????

Good point. I've done a bit of testing on this issue.

http://www.rv8.ch/article.php?story=2005052420523369

I'm not yet sure I have a 100% perfect solution to the problem of water. Of course, I don't expect to get too much into the system. If you know of a 10 micron filter that does not clog with water, that would be great info!

Mickey,

A gascolator IS a water separator AND a filter........Why are you re-inventing the wheel??????

Your diagram is beautiful, but I don't see any check valves........what keeps the pumps from backflowing during one pump operation?????

 

[RV8RIVETER]

How much water??

Yes, yes a gascolator catches water. And in a system that already has 3 filters, then it's ONLY function is to catch water.

But, in fuel injection system, the recirculation and high pressure flow mixes the small amounts of water that may occur during condensation with no ill effects on the engine. So, therefore only large amounts of water will have a major impact on engine operation and large amounts of water will fill the gascolator, rendering it useless anyway (because once it is filled it stops seperating).

From another source:

I reviewed the first 50 NTSB accident reports involving
water-contaminated fuel, as delivered by their online query routine
("water NEAR fuel").

The reports that have enough detail suggest that the most common cause
of the contamination is fuel entering the tank(s) from rainwater
entering the fuel filler. E.g., several inches of recent rain
showers,
and filler cap seals deteriorated. They cite also inadequate design,
where the tank drains do not evacuate from the very bottom of the
tank. Thus water collects in the bottom of the tank from either/both
entry via the fuel filler or condensate, over time. Especially in
those A/C where the pilot drains clean samples in preflight, while the
A/C sits nose-high, but "bingo," later in reaching level flight, water
begins flowing in enough quantity to cause engine stoppage. E.g., in
several of the above reports, "Pilot told investigators that some
water was found the fuel sample, but he continued sampling until
clear." Yet large quantities of water in the tank (and gascolator)
would be found at the accident site.

I have read elsewhere that the amount of water from condensate in even
an empty tank is too little to cause a big problem by itself in a
single cycle. The problem comes in many condensation cycles over
time, in the scenario above. Once water from humid air in a tank
condenses and makes its way down to the bottom, the air in the tank is
too dry for much more on the next cooling cycle. I doubt the tank
vent can exchange dry air for any significant amount of humid air
outside. But in 25 years of tank/sump draining on my AA-5, I have
never
sampled a drop of water. But water intake on AA-5's is a problem per
NTSB, if a cap seal is bad and the scupper drain is clogged (I do my
own annuals, as shops can miss this stuff!).

The design question seems to be whether one should be able to drain
the Europa tank, in addition to any gascolator installed. The
Europa-designed tank drains accomplish this. If you start sucking
water, once a downstream gascolator fills with water, it can't trap
any more. I'm not sure of all this, just tossing out for comment.
But the NTSB reports were eye-opening for me on this issue.

One advantage of a gascolator, in my meager understanding of all this,
is that fuel delivered with water in a fillup just prior to flight
takes so long to settle that an immediate fuel sample is useless. So
it becomes the "last line of defense." But note, though, in the above
sample reports, the FBO's fuel tested negative, where such testing was
cited.

Regards,
Fred F., A063, N3EU