Fuel Filter Advice

[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.