Fuel Filter Advice

[jiott]

Some good points Danzer, thats what is great about this forum. To answer your points: Yes water could collect in the rear of the wing tanks and be dumped into the system in level flight, but if that happened I believe it would be caught and trapped in the bottom of the header tank (providing there is enough room because you emptied it on your preflight) and could then be drained off at the next preflight. Unless there is such a large amount of water due to a long storage period that all bets are off and you really should have thoroughly drained all tanks in a level attitude before flight. I think any large amount of water that could overwhelm the trapping capacity of the header tank would also do the same to a gascolator. I also have a suspicion that the header tank may even possibly do a better job of separating water because it is bigger and the fuel flow turbulence thru it is less than in the smaller gascolator.

We are all just brainstorming here but trying to use sound engineering logic. As you say, a thorough and consistent preflight is still the most important thing of all, taking into account how long the aircraft has sat and in what conditions-outdoor, hi humidity, etc.

[Jerrytex]

I think you mentioned Earls. This and a gascolator is what I have. Cleanable/replaceable element

http://www.summitracing.com/parts/ea...FYtAMgodeDQAOA

[Paul Z]

I don't clean mine, I replace once a year. Cheap insurance

[Av8r3400]

Personally I won't use a filter in the line from the wing to the header. Gravity flow is insufficient, IMO, to prevent premature blockage. So if you have a glass filter there and see the blockage when you are overflying the sierras, it's still blocked...

I have a gascolator with screen in my yellow plane and will be installing an inline metal filter pre mechanical fuel pump in my project plane. (Probably a similar napa model like supplied by Kitfox)

Many people don't know that there is an unserviceable filter in the mechanical pump on a 912. I don't know the micron value...

[Paul Z]

I'm between the per verbal Rock and hard place. I have an SLSA, and technically I need manufacturer approval to change it.

[Danzer1]

Larry,

I'm not following your logic - nor am I arguing your right to your opinion.

Personally I won't use a filter in the line from the wing to the header. Gravity flow is insufficient, IMO, to prevent premature blockage. So if you have a glass filter there and see the blockage when you are overflying the sierras, it's still blocked..

Pressure or lack thereof does not cause a blockage, although a blockage does reduce the flow. The reduced flow can be caused by a clogged filter caused by too small a micron filter and/or infrequent cleaning interval and/or really crappy gas very frequently and/or the wrong type of filter (paper) and/or incorrect fuel pipe size. There are thousands with this type of setup working in all types of high wing aircraft, not just Kitfox's.

100 micron mesh should be more than sufficient for any carbureted engine as there are no passages, openings or jets smaller than .5 micron (that I am aware of) in any carb.

Just food for thought,
Greg

[Av8r3400]

Let me try to explain my thought.

A filter located on the suction side of a pump has the fluid drawn through it via the vacuum of the pump. Quite a powerful motivating force. A dirty filter will reduce flow but takes considerably more contamination to stop the flow.

A filter that is using only gravity to motivate flow is much more susceptible to minor contamination of the element stopping the flow, because the motive force of the fluid is far less. This is especially prominent in the case of an aircraft, where inflight motion causes inconsistent tank to line orientation, at times dramatically lowering the gravitational force.


I like to mitigate risk. To me, the risk of the use in these filters is something easily eliminated.

[HighWing]

A couple more thoughts.

In the original design the fuel outlet on the wing tank was at the trailing edge. In the ramp position on a tail dragger water might collect, but it would be in tablespoon amounts. The port was then moved to mid tank to help mitigate the problem inherent with long descents with low wing tank fuel loads unporting the aft located outlet. I guess this is an instance of a solution to one problem possibly creating another.

Fuel filters mounted between wing tank and header tank would be before the low fuel indicator sensor. Problems with fuel flow from the wing tanks whether it is caused by kinked fuel lines, inadequate fuel levels or clogged filters would be indicated first by the lowering of the fuel level in the vent tube - I like the clear tubes - or by the flashing panel light which would typically give 20 to 30 minutes of reduced powered flight to find a place to put the airplane down. In the event of a post header tank obstruction, that fuel flow reduction would be indicated by a rough running engine or the dreaded silence. Time for putting the airplane on the ground would be a best guess.

[Paul Z]

I think you mentioned Earls. This and a gascolator is what I have. Cleanable/replaceable element

http://www.summitracing.com/parts/ea...FYtAMgodeDQAOA

That is the same filter John McBean put into my SLSA. I have had no problems. I just replace one a year, which is probably overkill but that what I have been doing. I am concerned if cleaning it will really get the crud out. I can't see 35 micron particles.

[Danzer1]

Paul,
Are you sure it is a 2301 (35 micron) and not a 2302 (85 micron) - they look identical? Curious to know for sure what the factory uses!

Greg