RV inline fuel filter

[Notatestpilot]

Anyone install and have used this filter in their RV?(please see attached photo.)
Like to know if there’s any issues, essentially your review.
Thanks

 

[geezer]

Do you have a gascolator? They are expensive, but have about a century of incremental improvement.

They have the following advantages:

Filter at the top
Transparent lower container on most models, to see the water or debris, some are metal, must be drained to see what is there, or, not there
Integral drain to remove contaminants
Outlet at the top to the engine, will not pass water until filled


The filter you depicted is opaque, how do you know if it is full of water? Clogged with debris? How do you drain it periodically? If it clogs, your gas flow is stopped, even though you have plenty of gas, OK in a car, not in a plane.

Years ago, before I became a pilot, I bought an inline filter for my first new car, clear chamber, mounted vertical, it had a drain screw to remove water, and could be dis assembled to blow air through the filter element to remove debris. One of the gas stations I used had occasional problems, and this filter kept my carb clean.
It functioned much as an aircraft gascolator.























;

 

[Dan Thomas]

I think the OP is referring to a Recreational Vehicle (motorhome) rather than an RV-8 or whatever.

 

[Notatestpilot]

Nope!
My RV6....thanks.

 

[nauga]

Are you proposing using this on the feed from each tank? Or a single in the main feed? Bypass? My first reaction was that if the screen gets blocked or even partially blocked you'll have no fuel or restricted flow. At least it doesn't look like it has an element that will swell up and block if it swallows water, as some are prone to.

Nauga,
who prefers a gascolator

 

[Dan Thomas]

Nope!
My RV6....thanks.

Don't use it. As Nauga says, you can't monitor it or drain it before flight.

 

[kmacht]

They are common on the sonex line of aircraft. A gascolator doesn’t work with the aerocarb because the aerocarb needs to be the lowest point in the fuel system with a straight downward sloping line from the tank or else vapor bubbles cause the engine to stumble. These in line filters are the only thing that works in the limited space available and are what the factory uses instead of a gascolator now. Standard practice is to replace them every annual. There is also a tank finger strainer before the fuel gets to the filter. Some have also used the ones with a clear housing that can be inspected before flight but they are not made as well. The sonex is a pure gravity fed system so if you have a fuel pump on your RV then your experience may be different. If a gascolator works in the standard RV setup I also wouldn’t recommend deviating from it unless there is a really good reason.

 

[Dana]

Transparent lower container on most models, to see the water or debris, some are metal, must be drained to see what is there, or, not there
Integral drain to remove contaminants
Outlet at the top to the engine, will not pass water until filled

I don't think anybody makes a clear bowl gascolator for airplanes any more, might have been an AD to replace the glass with a metal tube? Only glass ones I've seen in recent years are for small engines and antique cars, with no drain.

 

[geezer]

Our 1960 Cessna 150, and 1962 172 had glass, and I think our next one did too, but later ones had metal. Always drained some fluid on preflight. One required 2 people, as the drain was cable remote from the oil filler hatch, drained under the cowling, lazy check, drain until sure that the puddle was gas, no beads of water.

 

[donjohnston]

Velocity's run these. While not exactly the same, they appear similar.

#6 40 Micron Maintainable Fuel Filter - AIRFLOW PERFORMANCE

FUEL FILTERS MANUAL 40 Micron Filter Element

airflowperformance.com

Has worked fine for me. I cleaned about once a month until I stopped seeing fiberglass dust in it. That took about a year.

I haven't seen a gascolator on a Velocity in at least 20 years.

 

[tsts4]

99.9% of the US built RV-10s, myself included, run a similar inline fuel filter with no gascolater.

 

[FORANE]

Interesting so many use this sort of filter. I'm a big fan of experimental but apart from a few aforementioned specific use cases, why divert from the well trodden path in such a critical component?

 

[kyleb]

Interesting so many use this sort of filter. I'm a big fan of experimental but apart from a few aforementioned specific use cases, why divert from the well trodden path in such a critical component?

In the rv’s, you’re gonna find any water in the fuel when you sump the tanks. Beyond that, gascolators are a really good way to add heat to your fuel and cause hard hot start and other warm fuel problems.

I have a gascolator on my carb’d RV-6 but have an inline filter on the RV-10, which is fuel injected.

 

[Daleandee]

They are common on the sonex line of aircraft. A gascolator doesn’t work with the aerocarb because the aerocarb needs to be the lowest point in the fuel system with a straight downward sloping line from the tank or else vapor bubbles cause the engine to stumble. These in line filters are the only thing that works in the limited space available and are what the factory uses instead of a gascolator now. Standard practice is to replace them every annual. There is also a tank finger strainer before the fuel gets to the filter. Some have also used the ones with a clear housing that can be inspected before flight but they are not made as well. The sonex is a pure gravity fed system so if you have a fuel pump on your RV then your experience may be different. If a gascolator works in the standard RV setup I also wouldn’t recommend deviating from it unless there is a really good reason.

I just wanted to put in my 00.02 to say that my particular gravity fed aircraft with a Marvel Schebler carb has a gascolator ...

 

[kmacht]

I just wanted to put in my 00.02 to say that my particular gravity fed aircraft with a Marvel Schebler carb has a gascolator ...

My comments were specific to the aerocarb. A marvel Schebler carb has a float bowl that allows for any air bubbles to not interupt the engine. The aerocarb has no float bowl so any interruption in fuel flow, even a small vapor bubble interrupts the engine and makes it stumble. I don’t recommend it for an RV but that is why many Sonex use that inline filter instead of a gascolator.

 

[Daleandee]

My comments were specific to the aerocarb. A marvel Schebler carb has a float bowl that allows for any air bubbles to not interupt the engine. The aerocarb has no float bowl so any interruption in fuel flow, even a small vapor bubble interrupts the engine and makes it stumble. I don’t recommend it for an RV but that is why many Sonex use that inline filter instead of a gascolator.

I'm aware of the difference between a slide carb & a float bowl carb. I tinkered & flew an aerocarb for ~200 hours. I don't have any intention of ever flying behind another one. I have reasons for that but mostly because of the hesitation and stumbles that are caused when using them. Here's an example:

Engine stumbles during take-off

The aerocarb is the reason some Sonex aircraft have ditched the gascolator. I'm not certain that's a great idea ...

 

[Dana]

Another issue is that the VW derived engines which power most Sonexes won't windmill due to the small prop and thus won't automatically restart when fuel is restored... one more reason you don't want it to "stumble".

 

[Dan Thomas]

I don't think anybody makes a clear bowl gascolator for airplanes any more, might have been an AD to replace the glass with a metal tube? Only glass ones I've seen in recent years are for small engines and antique cars, with no drain.

I have one. It came off my Jodel. That glass cylinder was 1/4" thick but I still didn't trust it. The head was cast zinc, so the total weight was not airplane-friendly. They were meant for tractors of the 1930s and '40s. I machined an aluminum gasolator for the airplane.



The brass screen came from a reusable coffee filter. The bowl bolt was stainless.

 

[455 Bravo Uniform]

Nice!

Any concern with SS bolt into aluminum threads? Galling? Galvanic corrosion? Or is there a threaded fitting in the top?

I know enough to be cautious, but that’s about it.

 

[Dan Thomas]

Any concern with SS bolt into aluminum threads? Galling? Galvanic corrosion? Or is there a threaded fitting in the top?

Some say there is, but I have seen stainless sheet riveted to aluminum, chiefly as firewall sheet to aluminum fuselage. After many decades it's still there in every airplane I've worked on. I've also seen stainless fuel fittings used in aluminum bulkhead fittings in large-aircraft tanks. Then, of course, there are the many stainless exhaust systems bolted to aluminum cylinder heads. Sometimes the flange gaskets are stainless, too. In Lycomings, the spark plug threads are a stainless Helicoil in that aluminum head.

Galling is a problem, but usually with stainless threads into stainless threads. We used Nickel Anti-seize there.

The bolt threads were tapped directly into the aluminum head in my gascolator.

The Cessna 180/185 and oldest 182s have stabilizer trim jackscrews. These had, originally, steel screws that ran in steel tubular nuts, all in an aluminum housing. Corrosion was a big problem, especially with airplanes on floats, and especially in salt water. The galvanic action between the aluminum and steel was no doubt a factor. These parts are obscenely expensive from Cessna, so McFarlane came out with stainless screw and nut and stainless chain, and the original aluminum housing is used in the rebuild. The kit comes with a new stainless chain, too. Much better than the old steel chain.



One part that McFarlane doesn't have is the mounting bracket. Cessna calls it a "hinge." It's the item pointed to in the picture here. About the size of a golf ball.

Before I retired six years ago they wanted, if I remember right, seven thousand bucks for one. There are left and right in each airplane. Two jacks. That hinge is probably just 7075T-6 or similar, and could be made with a lathe and mill, but if it fails you lose trim control. If they both break you crash. Monstrous liability.

 

[Spring Ford]

Any concern with SS bolt into aluminum threads?

There is - if you have a boat on the ocean.

Commonly used and the recommendation often seems to be remove bolt and re-apply anti-seize every year.

No one seems to bother. And they sometimes snap off on attempted removal.

On an aircraft, I think it will probably last a long time.

 

[unsafervguy]

i have been using the summit version of that for 22 years, never found more than a few specks in it when i clean it. a gascolator on a tailwheel aircraft is just a heat sink. it does no good, as it is not at the low point of the system. most RV's live indoors, and never see rain. put it in and clean it every condition inspection, it will work fine.

 

[Lndwarrior]

Have you checked the Vans Air Force website? They have mountains of data on this subject. And those folks get into the real weeds on this issue, including actual test data.

 

[Dan Thomas]

i have been using the summit version of that for 22 years, never found more than a few specks in it when i clean it. a gascolator on a tailwheel aircraft is just a heat sink. it does no good, as it is not at the low point of the system.

But the critical time when the gascolator is needed is when the airplane is NOT in gorund attitude. That's when the fuel is flowing from the tanks to the engine, and the gascolator does indeed trap moisture and debris. As a mechanic and commercial pilot I've seen it often enough.

Do these attitudes look like a gascolator wouldn't be at the low point in the system?







For airplanes that have spots in the fuel system lower than the gascolator, there are provisions to check for moisture and dirt. Cessnas, for instance, have this in their inspection checksheets in their service manuals:




That selector valve is right at the bottom of the belly. It comes with a 1/8" pipe plug in the drain. You don't want to know how many I found seized into that valve because they hadn't been out in 40 years or more. I took them out and installed a quick-drain valve in the flight-school airplanes. When I got the plug out, there was quite a gob of gunk and dirt and stuff in there.

 

[Dana]

a gascolator on a tailwheel aircraft is just a heat sink. it does no good, as it is not at the low point of the system.

On all of the [tailwheel] airplanes I've owned (Taylorcraft, Kolb, Fisher 404, Starduster, Hatz, Parrakeet), the gascolator was indeed the low point of the system, both in flight and on the ground.

 

[kyleb]

On all of the [tailwheel] airplanes I've owned (Taylorcraft, Kolb, Fisher 404, Starduster, Hatz, Parakeet), the gascolator was indeed the low point of the system, both in flight and on the ground.

The reason “low point in the system” matters is because it gives you head pressure when you sump the gascolator. No head pressure = no flow. The important things about a gascolator are the screen and the fact that the bowl acts as a small reservoir and allows water to precipitate out to the bottom of the bowl where it will not be picked up and sucked (or pushed) downstream.

 

[Datadriver]

I lost any love for gascolators when the top of mine came loose and the engine began sputtering and gasping. I had a field repair done using safety wire to tighten the top of the bowl.

gasolator top loose video

 

[Dan Thomas]

I lost any love for gascolators when the top of mine came loose and the engine began sputtering and gasping. I had a field repair done using safety wire to tighten the top of the bowl.

gasolator top loose video

Not a gascolator quality problem. It was either lousy maintenance practices, or a gascolator that was well past its best-before date.

Run without a gascolator and you soon realize why it's there.

 

[Dan Thomas]

The reason “low point in the system” matters is because it gives you head pressure when you sump the gascolator.

The real reason it matters is that water and dirt are heavier than gasoline, and will settle in low spots. A fuel line with a low spot can accumulate water until the flow is enough to suddenly shove it farther downstream. Or it can accumulate there and freeze and restrict fuel flow.

 

[kyleb]

The real reason it matters is that water and dirt are heavier than gasoline, and will settle in low spots. A fuel line with a low spot can accumulate water until the flow is enough to suddenly shove it farther downstream. Or it can accumulate there and freeze and restrict fuel flow.

Exactly. You need a “local” low point to capture the bad stuff. But you need a systemic low spot so gravity allows you to drain it. Put that gascolator up high and it’ll still catch the stuff. But it ain’t gonna drain very well.

 

[Dan Thomas]

Exactly. You need a “local” low point to capture the bad stuff. But you need a systemic low spot so gravity allows you to drain it. Put that gascolator up high and it’ll still catch the stuff. But it ain’t gonna drain very well.

There are system drains that are very high. We see examples in nearly every fuel tank: the sump drains, and they work fine.

Another, less-relevant example are the fuel vent line drains such as those in the Cessna Cardinals. They're there to drain moisture and and crud from that long vent line that runs from the outboard front of each tank, aft and around the rear of the tank and all the way to the opposite wingtip. The low spot in those lines are at the wing roots, where we find a tee with a plug in it that is supposed to be drained regularly. And how often does that happen? Ha. Fuel can lay in there while the airplane is parked for long periods, and it evaporates and leaves varnish that accumulates with repeated cycles.

Item 12, here. It's a 200-hour/annual item.



Item #6 is the drain fitting, shown in two places, in the right and left wing roots:



This loopy arrangement prevents the "Cessna drip" out of the fuel tank underwing vents when the tanks are full and the airplane might be parked left wing low.

 

[geezer]

Dan, you have an amazing reference library.

Speaking from the point of view of one who had one, in a different field, and has recently down sized, do you have a recipient picked out to be the next owner?

Are they enough younger than you to get a lot of use before they retire?

They can end up in the trash if you do not haver a plan in place, well before your self reliance slides.

I transferred my collection of manuals, instruction books and notes in three stages, in my 80's. at 89, when we moved out of our house, the remaining material went into paper recycling. 40 years of work reports, some with complex diagrams of how things worked, went out. I will miss occasionaly pulling one at random, and relive some of my history. No value to any one else, so trash.

You need to find that, or those people now, while your mind is sharp, and be sure they know they are going to receive it. The list should be with your will.

Clear hindsight from 90 years old, but, fortunately, still active, to a limited degree.

 

[Gary Ward]

Dan, you have an amazing reference library.

Speaking from the point of view of one who had one, in a different field, and has recently down sized, do you have a recipient picked out to be the next owner?

Are they enough younger than you to get a lot of use before they retire?

They can end up in the trash if you do not haver a plan in place, well before your self reliance slides.

I transferred my collection of manuals, instruction books and notes in three stages, in my 80's. at 89, when we moved out of our house, the remaining material went into paper recycling. 40 years of work reports, some with complex diagrams of how things worked, went out. I will miss occasionaly pulling one at random, and relive some of my history. No value to any one else, so trash.

You need to find that, or those people now, while your mind is sharp, and be sure they know they are going to receive it. The list should be with your will.

Clear hindsight from 90 years old, but, fortunately, still active, to a limited degree.

I have been learning from Dan the last 4-5 years. I have often thought/wish I could capture his knowledge and store it somewhere other than in my weak mind.

At least some of it is here in POA.
Thanks Dan.

 

[Dan Thomas]

I don't have an extensive paper library. I had all that stuff in the shops I worked for. In the flight school I bought it for the shop and left it there. I took only my textbooks.

Most of what you see is right off the internet. That fuel system stuff is out of an online copy of the 1968-'77 177 service manual. There are plenty of such manuals if you Google for them. Some are from sellers of such stuff, but others are free from people who upload them. They won't all be current, but they're often good enough.

If you check the table of contents in the front of these manuals, you can find what you want. Sometimes it takes patient scrolling. It sure does on my old laptop.

I copy diagrams out of those manuals using the Windows Alt-Shift-S combination, holing them down and selecting the section I want with the mouse. Maybe it's not Windows? Might be a function of my Brave browser.

 

[donjohnston]

Not a gascolator quality problem. It was either lousy maintenance practices, or a gascolator that was well past its best-before date.

Run without a gascolator and you soon realize why it's there.

Define "soon".

I've run without a gascolator for 10 years. Haven't had any problems. I personally know about a dozen planes without a gascolator that have been flying for over 20 (some at 30 years) without any problems.

 

[Dan Thomas]

Define "soon".

I've run without a gascolator for 10 years. Haven't had any problems. I personally know about a dozen planes without a gascolator that have been flying for over 20 (some at 30 years) without any problems.

It only takes one bit of contaminated fuel. If you are using Mogas, it will usually have ethanol in it, which absorbs water and disperses it so it flows through. 100LL won't do that.

Leaky fuel caps are responsible for much water in systems.

 

[donjohnston]

It only takes one bit of contaminated fuel. If you are using Mogas, it will usually have ethanol in it, which absorbs water and disperses it so it flows through. 100LL won't do that.

Leaky fuel caps are responsible for much water in systems.

Once again, define "soon".

And what gascolator will remove a pint of water from fuel?

 

[Spring Ford]

Windows Alt-Shift-S combination, holing them down and selecting the section I want with the mouse.

Thanks, I had never used the hotkey to access this. It's a Windows facility, certainly in Win 10.

It seems to be WindowsKey-Shift-S. This starts the Snip & Sketch application but without the sketch bit available. There is no need to hold anything down after it has launched.

After starting with WindowsKey-Shift-S you can "upgrade" to get the sketch facility by clicking on "Snip & Sketch".



I have Snip & Sketch on the task bar. Maybe I will try the hot key. I do use the sketch bit quite a lot though to highlight relevant parts of the screenshot as shown above.

 

[Dan Thomas]

Thanks, I had never used the hotkey to access this. It's a Windows facility, certainly in Win 10.

It seems to be WindowsKey-Shift-S. This starts the Snip & Sketch application but without the sketch bit available. There is no need to hold anything down after it has launched.

After starting with WindowsKey-Shift-S you can "upgrade" to get the sketch facility by clicking on "Snip & Sketch".

View attachment 131863

I have Snip & Sketch on the task bar. Maybe I will try the hot key. I do use the sketch bit quite a lot though to highlight relevant parts of the screenshot as shown above.

That's it. I mistakenly called out the Alt key instead of the Windows key. I don't even look at them. Alt gets used for a lot of ASCII characters that aren't on the keyboard.

 

[ateamer]

I have been learning from Dan the last 4-5 years. I have often thought/wish I could capture his knowledge and store it somewhere other than in my weak mind.

At least some of it is here in POA.
Thanks Dan.

I’m working on assembling a document with Dan’s and Magman’s posts, plus a few others. It’ll be a fair amount of work, but will be a great maintenance bible.