Fuel system and filter

The 912 Installation manual doesn't directly specify the requirements for the coarse filter. The entire section reads:

"COARSE FILTER
On fuel tank as per valid certification."

What 'as per valid certification' actually means will depend on how your aircraft is certified. I'm unfamiliar with the requirements for ULM aircraft in France but I'd guess it would be acceptable to comply with CS-VLA 977 (b), which states:

"There must be a strainer at the outlet of each fuel tank. This strainer must -
(1) Have 3 to 6 meshes per cm;
(2) Have a length of at least twice the diameter of the fuel tank outlet;
(3) Have a diameter of at least that of the fuel tank outlet; and
(4) Be accessible for inspection and cleaning."

This equates to a mesh pitch of about 1.7 to 3.3 mm. (or for our US friends, 8 to 16 meshes per inch, per FAR 23.977)

Accounting for the thickness of the wire, this should filter out particles larger than approximately 1200 to 2400 µm.

For example:

Many thanks @tim B, exactly what i need ! perfect !  

All the best. 

Nicolas. 

Hi Nicolas,

I would advocate against the traditional in tank strainer.

Instead would suggest an easy to inspect, almost indestructible, light weight, easy to replace in the field, low cost, in line, gauze, filter, on each supply line, such as the HENGST H102 WK (or 103) see below (Note: other manufactures are out there)

My reasoning is simple;

The traditional heavy course strainer, serves only to catch course particles (eg occasional insect)

Can not easily be inspected, particularly if tank contains fuel.

Requires removal from the tank to service - fuel tank must be emptied to do this.

A second, down stream finer filter, must be used, to remove particles that may block carburettor jets etc.

The one good feature of the finger strainer is;

The in tank strainer will help, maintain fuel flow,  should your fuel tank be constructed of/lined with. material that may shed large flakes that have the potential to block the fuel outlet port.

NOTE: Good refuelling hygiene (filter funnel) will minimise the risk of filter blockage.

😈

Don't use plastic filters if your auto fuel has ethanol. Fight Design tried that and the filters softened and started to bend the fitting ends. They put out an SD and had people use reusable metal filters.

Hi Roger,

I cant say I have tested the filter type, I have recommended, with Ethanol blended petrol BUT they are produced by  reputable, long serving filter manufactures, that I would expect to be selling only products that will meet the latest standards (ie including fuel containing ethanol).

The HENGST and Baldwin filters that I have used, are quality products, that are installed as OM fittings in many European light aircraft & road vehicles - I doubt they would do this if there was even a hint of them being unsuitable.

If in doubt - acquire a filter, place it in a jar of ethanol blended petrol (or pure ethanol for a quick result). Check the integrity of the filter casing at intervals. When you get to two years and the filter is as good as new, you have likly demonstrated that the filter is ethanol resistant😈