Gascolator

Hello Experts,
1. A gascolator is first used for water separation? - Correct?
2. It is also a filter for the smallest particles to protect nozzles from clogging. - Correct?
3. What does the gascolator do with the collected water, if there is any at all? - Is the water drained automatically?
4. How fine is the filter in the gascolator, is it fine enough to prevent nozzles from clogging?
5. How large is the filter area in a Gascolator compared to a normal fine filter such as a Hengst HG 102?
6. And last but not least: If you only have a fine filter and there may be some water in the gasoline, the water/gasoline mixture can pass through the fine filter. It is not important here what effect this has on the engine running, but whether the water could block the fine filter.

As far as I am concerned, I have a simple 912 80 hp without a gascolator but with a Mahle Knecht KL 145 fine filter. Gasoline almost only E0 = without alcohol, if E5 then the tank contents are almost always emptied on cross-country flights. No extreme climatic conditions in Europe, have never noticed water when draining although I have a metal tank and the tank is usually only half full.

If you often have a humid climate and the petrol has a high water content then I could understand the need for a gascolator, but I would need to know exactly what such a device really does and whether an additional fine filter is necessary or whether it is simply too much and just poses a further risk.

Hence the basic questions, so that I and possibly others can make their own decision based on their specific situation.

Regards

Hi HKK

1  water and dirt or other debris  It must be mounted at the low point in your fuel delivery line.  Normally at the bottom of the firewall.

2  yes, see above

3  you must drain some off before each flight.  Gascolators have a drain valve and it will be called out in your preflight checklist. 

4  how fine depends on what gascolator you purchased,  They can be from 70 to 120 microns, check what you need for your engine in the installation manual. 

5  Filter area again depends on what you purchased,, they are not all the same

6  the design of a gascolator allows water to drop out of solution by its design.  This way when you "sump" the gascolator you will know if you have water or not in the system. 

You have noted a very specific climatic area and this also depends on the fuel you have available.  I can personally tell you from flying in Florida, where I got my PPL we had aircraft with all metal tanks.  The practice, and still recommended, is for an aircraft with all metal tanks to fill them up at the end of the day so they are full.  At night, when the temperature drops and becomes even slightly more humid, condensation will accumulate inside of the air space of the tanks.  Every morning before  flight, especially using Avgas with no Ethanol, you will sump the tank and get a bit of water.  The larger the air space in the tank the more water is found.  

What you also need to consider is if anyone has ever found an spots of corrosion inside the float bowl of a carburetor Rotax...that is water.  The same thing is happening, the air space, vented to the atmosphere, can get some drop out from the fuel and this water will accumulate due to the float bowl design.  (the small "well" inside the float bowl casting is to stop water/contamination from getting into the main jet}

In the case of a Light Sport aircraft made to FAA/ASTM standards you can't use any plastic or flammable filters in the fire zone (firewall forward) they have to withstand 2000F / 1090C for 5 mins without failing.  (firewalls are for 15 mins) 

Cheers

Hi Rotax Wizard,

Thanks for the info.
If I understand you correctly, a gascolator fulfills two tasks: To separate water and to filter particles.
In other words, if my airplane has a drain valve directly at the lowest point of the tank and a fine filter is installed in the fuel line, then it is practically the same thing, except that the functions are split.

Because, as I have learned, I open the drain valve before moving the airplane to drain water, so I don't need a gascolator to separate water. It is practically the same whether I operate the valve of the gascolator or the drain valve of the tank.

If you have the situation that there is no possibility to drain the tank directly a gascolator is needed or better is mandatory.

I have taken note of the information regarding humidity and condensation, I think everyone agrees.

Nevertheless, the theoretical question again: water in the tank, no gascolator installed, no possibility to drain or I don't drain the tank directly because I'm simply too lazy, will the fine filter become blocked by the water at some point or will the water/petrol mixture pass through the fine filter?

Have everyone experience about this?

Greetings

Hi again

if you are flying a low wing aircraft and you drains are the lowest point perhaps you are right, no need for an additional gascolator, this you would have to verify.  If it is a high wing, like many aircraft, the gascolator is still considered necessary as sits much lower and water, debris as well, will always tend to find the lowest point.  Water in particular will never float on the top of fuel as you know.  The question of your fine filter I simply can't say.  Your fine filter also should never be a paper element, water will expand the material and restrict flow.  To answer your question, no, a fine micron mesh filter will not trap water.  Water is from 2 to 5 microns so flows past a normal screen filter even with tiny 10 micro size.  It is more for debris in your fuel.  The gascolator allows this to drop out so you can determine if you have water.  

In a certified installation for an aircraft I have never seen one without a gascolator.  In an experimental it's up to you.  If this was a kit aircraft perhaps contact the kit supplier and see what they recommend?

Cheers

Musings;

Nothing wrong with the Gascolator. Old design/concept, much room for improvement ( see earlier comments).

I do not see the fitting of any particular piece of equipment/system to a Certified aircraft, being a deal breaking argument, to do the same to a home built. WHY? Certified aircraft systems are, of necessity, built to ultra conservative standards. Certified systems are not changed without EXPENSIVE testing, research & deliberation. If it's not cost effective to do this, the status quo will be maintained eg Gascolator fitment.

In-line filters  have been successfully used, in small aircraft, for at least the last 20 years, ground based engines for far longer - stood the test of time.

The advice not to fit "plastic" filters in the engine bay is good but need not prevent the fitting elsewhere in the fuel supply system (possibly in a more easily viewed/accessible location). Also there are metal & "glass" in-line filters - I don't like them much but they do negate this argument.

Gascolators at the lowest point in the fuel system (usually engine bay) is an illusory benefit. IF your fuel tanks have been correctly designed/fitted, they will have an effective sump & a sump drain/valve. IF you do proper preflight checks you will use your sump valve to drain off any free water and most solid contaminants, at this point, BEFORE they enter the fuel delivery system.

In-line filters can have far larger filter area, than a Gascolator, allowing for much higher filter contamination, before fuel flow restriction (engine loss of power).

Do not use pleated "paper" filters as these can be heavily contaminated, before a visual inspect recognises the problem. 

In-line filters are a viable option, to the good old Gascolator.😈