Fuel filtration

From the 912 installation manual,  74-100 microns.   See Section 73-00-00, page 7.  

The gascolator is just okay for a filter, but also placed there at a low point in case of water. If you have a fuel usage meter like the RED CUBE many use then you are supposed to have a fine mesh filter before that.

Thank you both.

The Sonex/Rotax  I am building is pretty much finished - just tiding up loose ends.

I purchased an unfinished project. The original builder has installed the fuel system, including the gascolator (in the lowest point). Unfortunately he has no filtration before the boost & transfer pump - I will have to work out a way of retrofitting an in line filter before each of these.

With Jeff's reference, I now know that the 74 micron gascolator is the way to go. The down side is the very small filter area that will need  assistance from upstream in line filtration.

From Randy R Allen, Baldwin Filters Technical Advisor

"Nylon mesh is generally 200 mesh, which is 75 micron.  If the filter uses wire mesh it is generally 100 mesh, which is 144 micron."

So I guess I can either put a finer filter (50 - 75 mu) down stream of the gascolator (120 mu) 

OR

Use a fine screen in the gascolator (74 mu) that may be assisted by a course screen  (150 mu) up steam of the gascolator.

Sean,

The Rotax 912 installation manual is worth reading in detail, see the attached fuel system diagram from section 73-00-00.  This common design has a large mesh finger screen at each tank outlet, feeding into the selector valve, and then on to the gascolator which also serves as the fine filter. The finger screens in the tanks would be quite coarse, something like #16 mesh (1100 microns) so that they won’t become clogged with typical particles found in fuel.  I like this arrangement because the gascolator is easy to inspect/clean and you don’t need to be concerned with a downstream fine filter that may become clogged.  Also, while servicing the gascolator, it’s easy to quickly flow test the fuel lines between the gascolator and tanks to make sure the finger screens are not getting dirty.  

Typical finger screen…

https://www.aircraftspruce.com/catalog/appages/fingstrainers.php