Gascolator?

[Skippydiesel]

There is a suggestion here that I am against gascolators - I am not. Just like I am not against the good old moldboard plough - I just believe, that for light sport aircraft, there is a better system - in line, lightweight completely leak proof, transparent casing, gauze filters.

All of the naysayers can only come up with, is the gascolator is tried and true (like the moldboard plough) and that why you use them, good-on-yah! You probably drive a Model T Ford's - great car in its time.

[Onex107]

I removed the gascolator from my Onex due to temperature problems. Fighting the "Burps" I insulated all the fuel lines but could not do a decent job insulating the gascolator. I didn't want to add another blast tube for that.
Come to think about it. My 2005 car ran for almost 20 years, parked outside, and never had a water problem and I burned the same gasoline, from the same gas station, in the Onex. I guess I was lucky.

[Kai]

I am enclosing a screen dump from the installation manual Rotax has published for the 912 ULS. I don´t think it leaves much room for experiments.

[Skippydiesel]

Kai,

"I am enclosing a screen dump from the installation manual Rotax has published for the 912 ULS. I don´t think it leaves much room for experiments."

Last time I checked my Sonex legacy is an experimental aircraft - every part of it can be modified to suit the builder - including the fuel (filter) system.

As I have said the Hengst H102 WK style filter has been in common usage for at least 20 years (both kit and factory builds). I have yet to hear of a incident, attributed to this sort of filter, when correctly installed (same with any filter or aircraft system).

Your gascolator will
Cost somewhere between US$125 -$400 and be expected to last the lifetime of the aircraft
If correctly installed, catch any free water in the fuel
Filter 74 - 120 microns ($4-$6) (depending on which little round screen you install)
Weigh about .23 kg - Without hose/tube fittings and other installation hardware
Depending on aptitude and installation may be messy to inspect/service - screen easily damaged.

A Hengst H102 WK In Line Filter
Cost somewhere between US $5 - $12. Replacement at every 100 hrs probably a good plan. Can be cleaned /blown out with compressed air but why bother - just put a new one in.
Will catch small amount of free water but nowhere near the holding capacity of a gascolator.
Filter down to around 70 microns (certain brands claim lower/higher filtration).
Have been around as diesel pre filters since at least 1975 probably longer - so well tested.
Weigh virtually nothing - carry a couple of spares if required.
Can be inspected in situ - no need to open
Can be installed on as many fuel supply lines as deemed appropriate (one on each tank and if separate the Boost Pump fuel supply). Removes the need for tank finger strainer. Best in an easy to see/preflight location.
Do not require any tools to remove install - pliers always handy.
Casing probably not quit as tough as an all metal gascolator but would require deliberate effort to damage. Probably better than a gascolator with a glass bowl.
In normal usage completely leak/odor free.
With a little care replacement spillage can be totally avoided.

In line filters will do the job for you but as always good refueling hygiene is a must ie minimise the chance of putting contaminated fuel into your tank(s)

[Kai]

Wow! Impressive!

Still- there must be a reason why the engine manufacturers prescribe the use of such a gadget- if nothing else maybe to keep the engine out of costly warranty repairs.

But, as previously mentioned by others in this thread: experimental means that in a lot of countries you can do what you want. In other countries it means that you can build it yourself without the benefit of CAA quality control, provided that an accredited civil organisation in advance has accepted the drawings and as long as you religiously stick to plans, instructions, and regulations.

[Skippydiesel]

"................as long as you religiously stick to plans, instructions, and regulation"

Fair comment/observation - do what you have to do, comply with whatever regulations are pertinent, to get your project into the air.

It hadnt occurred to me that the Sonex range (all kit or plans built) would be anything other than experimental.

In Australia the experimental designation (home built from plans or kit, occasionally from "scratch") allows the builder a very free reign.

[Murray Parr]

As much as I like to believe I am an expert, I chose to stick with what Rotax recommends! It's hard to believe but I think they know a bit more than me....
-I have the coarse filter in the tank. Anything coarser than that will wreak havick in the rest of the system.
-Then the gascolator low on the firewall which I sump before first flight of each day and after adding any fuel.
-Then an aluminum cased fine metal mesh filter with enough volume to have partial blockage and still supply fuel.
-All my fuel lines have AN fittings and are Teflon anti-static infused. I don't wish to replace rubber lines every 5 years as this is asking for a leak I believe; others may believe something different and that's ok.

I know you can be very careful with fuel hygiene etc. but if I was to ever land at a place where petrol sniffing is a problem (I don't understand it but yes, it is a thing) in a community, I can't control what the offenders may do whilst syphoning fuel from my tank. I plan on going nowhere near those places for that very reason but can't always be sure nobody has messed with anything in your absence.

[Skippydiesel]

Hi Murray,

-I have the coarse filter in the tank. Anything coarser than that will wreak havick in the rest of the system.
So you have a filter (intank strainer) that you may get to see every few years, at best. It could be holding insect bodies, flakes of paint, tank sealer, bits of windblown vegetation, etc - one day all these "bits" may combine to prevent adequate fuel flow to the engine - Good system? - I think not, when an excellent alternative exists, the inline filter located where you can check it before each flight.

-Then the gascolator low on the firewall which I sump before first flight of each day and after adding any fuel.
Good system/installation but costly, heavy and a fiddle to inspect/service.

-Then an aluminum cased fine metal mesh filter with enough volume to have partial blockage and still supply fuel.
Why would you follow the gascolator (assuming appropriate micron gauze filter) with a second filter ? - you are introducing unnecessary complexity, weight, purchase & servicing cost. You may also be stressing your fuel pump(s) due to additional flow restriction, without practical benefit.

-All my fuel lines have AN fittings and are Teflon anti-static infused. I don't wish to replace rubber lines every 5 years as this is asking for a leak I believe; others may believe something different and that's ok.
Given that most rubber hose installations, markedly reduce the number of mechanical joins required, methinks the chance of a leak is also markedly reduced ie you have it the wrong way round.

[daleandee]

As much as I like to believe I am an expert, I chose to stick with what Rotax recommends! It's hard to believe but I think they know a bit more than me....

Hello Murray,

I have three screens in my system with the first being the fuel tank finger strainer, then a gascolator screen, and the third is in the Marvel Schebler carb I have on my Corvair. I don't know but perhaps the Rotax carbs have fuel screens also. I use AN6 fittings on high quality fuel lines. It makes for a professional installation as opposed to barbed fittings, screw clamps, & cheap automotive hose and filters. Perhaps it's overkill but many experimental aircraft accidents are caused by loss of engine power and that's usually the fault of a poorly designed fuel or electrical system. It cost a bit more up front but years ago I learned that, "for a few pennies more you can go first class."

I'm also very dilligent about fuel sources (hygiene) and the gascolator is part of that program. I do a fuel flow test at every condition inspection. I used to have (it walked away recently) a long tube that had a curve in it so I could reach in and drain the tank by siphoning out fuel from the sump (kinda like a vacuum). I've never found trash in my tank but that won't prevent me from looking for it.

As I stated earlier, builders can do what they like with their builds but I just prefer to try and get as close to the old time tried and proven methods that have worked for decades in certified airplanes. I have a lot of "experimental" in my EX-AB airplane so I like to add as much professional as I can ...

Best,

Dale
3.0 Corvair/Tailwheel

[Skippydiesel]

Multiple, in line filters, should be avoided.

Simple physics - every filter on a line/pipe presents as a restriction/resistance to fuel flow.

The ideal would no filters at all. This is impractical - with the best will/care, some contamination will always occur (hopefully a filter will prevent its entry to the metering system)

Every filter, constriction and curve, in the fuel reticulation system, causes a reduction in flow.

The more restriction, the harder downstream pump(s) will have to work to deliver the fuel, to the metering system.

Passing fuel through consecutive, in line filtration, is not only unnecessary, it goes against the principles of filtration (more is not necessarily better), hydraulics, minimising complexity and weight.

Rotax fuel filtration standard is 70-100 micron - this can easily be achieved by passing the fuel through one appropriately sized filter. If you are concerned about filter blockage (& you should be) choose a filter with a large surface area (usually a bigger filter) that can accommodate more contamination before blockage occurs.

Having all your fuel go through one filter introduces a potential failure (critical) point. Should that filter block in part or whole, so the engine will be starved of fuel.

The best systems, have supply redundancy ie two supply lines, both with appropriate filters.

Small (often Rotax powered) aircraft can achieve this level of redundancy by having two separate supply systems (preferably from diffrent tanks or at least 2 pick up points). Efficient, light weight, leak proof, low cost screen, in line, filters can be installed on both lines.