philjac94

From time to time I get people coming to me with problems with pump voltage climing, eventually leading to pump related errors. A lot of the time it is because of a dirty fuel filter. The owner is generally confused as to why his fuel is so dirty and insists his fuel handling is good, it usually results in the poor old fuel vendor being blamed for supplying dirty fuel.

Chances are the fuel is not dirty as supplied but being poluted from your aircraft fuel tank.
As your powering down the runway, dust, dirt and even fine mulched grass is being sucked into your tank via the overboard vent. Obviously it is not doing this at a great or even easily noticeable rate but over time it surely is.
So for the sake of a couple of dollars it is pretty good insurance to fit a vent line filter, just make sure it has sufficient surface area as not to impede air entering the tank. The Sullivan dual mesh fuse looking filter is perfect for this application. Best part is that it is fit and forget as every time you fill your tank you flush anything trapped in this filter overboard to wherever you send your overflow. You will be supprised at how clean your downstream filters will remain.

kimhey

Good point, but regular maintainance (cleaning) of the fuel filter is also a good idea ..... and that goes for me as well


Kim

joeflyer

My Feedback: (48)

Dirt entering the vent has never been a problem for me. A filter will add restriction to the vent. This probably wouldn't be enough to affect normal operation, however you most likely would have to disconnect the filter to prevent tank balloning while filling.

Joe

FalconWings

My Feedback: (57)

Im with Joe. Vent on our models typically suck by default, I would not restrict the flow any further.
David

Thud_Driver

My Feedback: (1)

Well, I did get a really bad batch of jet fuel once.  I poured a pint into a clear container and a couple days later, the bottom was completely covered with sediment.  That stuff turned my UAT bag black and coated the onboard fuel filter in black crud.  After that, I added a second automotive pleated paper filter in line on my fuel jug.  One on the pickup and one external.

Since then, I have about 4000+ flights off the dusty, gritty dry lakebeds in California where it's normal to see dust blowing up behind the jet.  My UATs don' t much get dirty and the few times I've actually opened up the filters since then, they've been clean.

I'm sure everybody's milage is different but I'm not seeing dirt in the tanks from the vent.

philjac94

Wow 4000+ flights is pretty impressive, I hope thats not on the one airframe and engine, that would be like 16 bearing services.
I bet you don't really need a FOD filter either but you still have one. It is the same principle.
As for obstruction of our problematic vent systems at present, the filter must be odd suitable size not to impede on air entering tank as I said in original post.
One reason why those that use the BVM type AirTrap, don't notice the dirt in their tank is because at the end of the days flying and tanks are drained, any contaminates end up in your fuel can.

At the end of the day if you can't see a benefit don't fit one, if you can, then it's an easy mod to do.

Thud_Driver

My Feedback: (1)

The lakebeds have zillions of tiny rocks on the surface so a FOD guard is pretty much madatory (well, maybe). But, still, a lot of dirt goes thru the engines. I don't usually defuel airplanes at the end of the day. Whatever is in the tank stays there.

Here's some pics of how dirty an engine can get in the desert. Before anybody complains, that engine went 104 hrs without maintenence or an o-ring. I did clean it up once in awhile.

wojtek

My Feedback: (73)

I would not put a filter on the vent side. You are asking for far more problems than that of any dirt getting in over time. There is a bigger chance of a flame out from a clogged vent than there is from a dirty filter. The fuel filters need to be checked every few dozen flights , cleaned/replaced when necessary.


~V~

philjac94

I could not have asked for a better photo than yours to support my original post. All that fine dust must be sucking into your tank via the vent, think of it, if your tank is 2 litres full of fuel, when it's empty it has been displaced by 2 litres of air and anything that is in that air. Like I said it won't be much, but it will be there.

PS if your fuel lines are anything to go by I doubt you would see anything through you AirTrap :-)
Before I get shot down, I'm not suggesting your fuel lines are dirty, just stained, got to love MJ-II.

philjac94

philjac94

Now why did you back up your point by saying a vent filter would be "clogged" and a fuel filter would only be "dirty"?? Of course in that situation the engine run condition will suffer, but so it would if it was reversed.
A vent filter gets back flushed every time you fill up, unlike your fuel filter.

philjac94

Oops updating via Iphone not a good thing, when you have little or poor reception..