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  #11  
Old 10-21-2014, 03:03 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
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A gascolator serves no useful purpose on FI equipped aircraft with return fuel layouts past the fuel filtering part which is more easily and less expensively taken care of with a simple filter than can easily be inspected/ cleaned. Unfortunately TC paints all installations with the same brush.

One fellow out here with an EFI equipped RV10 applied for an exemption under some different inspection text and was granted it after a short fly off time. I'll try to track down the details of it if I can.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 427.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #12  
Old 10-21-2014, 03:52 PM
Bevan Bevan is offline
 
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I did a gascolator on each side, one for each tank, mainly for ease of plumbing but also provides a seperate filter for each tank, right at the tank. Immediately prior to the gascolator, I have installed a mini ball valve for fuel shutoff during maintenance so I can remove the gascolator's bowl with minimal fuel loss due to siphoning. The ball valve is safetied open. I believe it was this one..

http://www.summitracing.com/int/part...2erl/overview/

Not flying yet so I cannot comment on how well it actually works but I am not anticipating any problems. It is all easily removable to revert back to the traditional way if needed. Not advocating anyone else do this without independant analysis. Be careful.

Bevan
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O-360-A1F6 (parallel valve) 180HP
Dual P-mags
Precision F.I. with AP purge valve
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Grand Rapids EFIS
Located in western Canada
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  #13  
Old 10-21-2014, 04:30 PM
Canadian_JOY Canadian_JOY is offline
 
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Location: Ontario, Canada
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Quote:
Originally Posted by Ironflight View Post
My memory might be completely failing, but I don't recall there being a gascolator on my Grumman Yankee, a U.S. Certified aircraft that I know was owned by many Canadians.That might possibly be an avenue to explore.
There is no gascolator per se in the Grumman 4-seater AA5-series aircraft either. They do have low point drains (sumps) in each wing root, and the electric fuel pump, located between the tank and the engine-driven fuel pump, has a filter screen which is cleaned annually or every 100 hours, whichever comes first. These engines have carbs rather than injection.
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  #14  
Old 10-21-2014, 06:01 PM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
A gascolator serves no useful purpose on FI equipped aircraft with return fuel layouts past the fuel filtering part which is more easily and less expensively taken care of with a simple filter than can easily be inspected/ cleaned.
I don't follow, perhaps I just don't understand fuel-injected systems.

As best I understand it, the fuel comes from the tank, goes through a filter (or gascolator), into the FI system, and there's a return line from the FI system back to the tank. The return line never supplies fuel *to* the FI system, it's just a return line. Your primary line *out* of the tank is filtered. So why can't that filter be a gascolator instead of an inline filter?
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  #15  
Old 10-21-2014, 06:12 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Snowflake View Post
I don't follow, perhaps I just don't understand fuel-injected systems.

So why can't that filter be a gascolator instead of an inline filter?
Exactly- good question for TC. With an EFI/ return type system, as soon as you turn the pump on without the engine running, 100% of the fuel is returned back to the tank at very high flow so fuel is immediately all mixed up with any water that might be in there. It all passes through the engine with no harm done. Any water present is always kept mixed and evenly distributed within the fuel due to the high return rates, even at full power due to excess pump capacity.

Of course, we should still have drains in the low points as RVs already have by design.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 427.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #16  
Old 10-21-2014, 07:40 PM
terrye terrye is offline
 
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Location: Vancouver, BC, Canada
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Default Gascolator "requirement" in Canada

There have been many references to "carb" and "fuel injection" systems especially in connection with the Canadian requirement for a "gascolator" in the fuel system.

I think it is important to distinguish the different types of fuel injection systems before saying a "gascolator" serves no purpose.

1. Bendix (Precision Airmotive) type fuel injection systems. Common on RVs. Demand sensed by venturi in servo. No fuel return to the tank.
2. Continental type fuel injection systems. Not common on RVs. Demand not sensed. Excess fuel returned to tank.
3. Automotive style. As Ross says, excess fuel returned to tank.

So in my view, whether we call it a "gascolator" or a fuel strainer/filter/drain is less important than its function. For a Bendix fuel injection system I think a fuel strainer/filter/drain is an important part of the fuel system since it removes particulate contamination and provides a preflight inspectable capability (drain or sumping).

For an automotive style fuel injection system, given the inherent mixing of fuel/water perhaps a filter only is sufficient. Of course the fuel tank quick drains should always be checked preflight.

Unfortunately the Canadian regulations do not distinguish between the different types of fuel injection, thus the requirement for a "gascolator".

For my system with Bendix fuel injection, I will have an Andair 70 micron gascolator in each wingroot to protect the pump, and a Falls Filtration 17 micron gascolator on the firewall to protect the injection servo.
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  #17  
Old 10-21-2014, 07:55 PM
jrs14855 jrs14855 is offline
 
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Default Gascolator

A point that has not been discussed is the inherent danger of many typical gascolator installations on older GA aircraft. I am talking about the glass and metal bowl style used on many Pipers thru at least the 60's. The typical firewall mounted gascolator was at the very bottom of the firewall, so as to be at the lowest part of the fuel system. In even a minor fender bender these gascolators could be damaged and now you had fuel running all over. Also the Piper style gascolators were inherently fragile and could come apart in flight. A lot of these gascolators found their way into early EAB aircraft.
Many years later the Pipers with fuselage tanks were found lacking in their ability to remove water from the tank. This was addressed by an AD which installs a quick drain in the bottom of the tank with a line running overboard.
I much prefer a tank drain and a race car type all metal filter that can be cleaned at regular intervals.
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  #18  
Old 10-21-2014, 09:31 PM
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rv6ejguy rv6ejguy is offline
 
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The liability of a gascolator has been experienced by a number of people with EFI systems on their aircraft where ethanol attacked the O-rings or gaskets on the gascolator and they were mounted on the inlet side of the pumps (maybe not a great idea). Air was introduced into the system, engines leaned out or full blown vapor lock caused the engines to stop. Certain pump designs like Bosch don't fancy air in them at all and may fail to reprime which is bad news either way. Air in an EFI system on the high pressure side is unacceptable and a lot more dangerous than some water mixed up in there.

Obviously, if we are using ethanol laced mogas, we want to make sure all seals are ethanol compatible. If gascolators must be used, we recommend that are the high pressure type mounted downstream of the pumps. We recommend filters placed upstream of the pumps to keep junk out of the pumps.

The main causes of water in the fuel are leaking caps with the aircraft parked outside and aircraft parked outside for long periods with partially filled tanks and large daily temperature variations causing condensation. For aircraft parked indoors, the chances of getting any substantial amounts of water in the tanks or system are practically nil. Mogas and avgas from the pumps is well screened for water prior to pumping.

I have something close to 20,000 hours in cars and aircraft with EFI, never a water issue in all that time and I live in a climate which can have massive daily temperature variations. Have never found water sumping my aircraft either.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 427.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #19  
Old 10-21-2014, 10:42 PM
Bevan Bevan is offline
 
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Default My gascolator is much more than a water separator.

I actually don't mind having the gascolator in place. It serves multiple purposes but the 70 micron cleanable and easily inspectable filter of the Andair unit is a nice form factor for a filter, which I need upstream of the aux fuel pump anyway. The water separating and sumping abilities are additional features that may or may not be useful one day.

As long as the gascolator does not intruduce new risks such as letting air in (deteriorating O-ring) and absorbing heat, I guess I can live with it.

Putting the gascolator in the wing roots solves the heat problem, minimizes the risk of O-ring failures, and allows me to check the filter without making any fuel drips in the cockpit.

Bevan
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RV7A Flying
O-360-A1F6 (parallel valve) 180HP
Dual P-mags
Precision F.I. with AP purge valve
Vinyl Wrapped Exterior
Grand Rapids EFIS
Located in western Canada

Last edited by Bevan : 10-21-2014 at 10:45 PM. Reason: spelling
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  #20  
Old 10-22-2014, 08:14 AM
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riseric riseric is offline
 
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Thanks for all the great inputs!!!

Sorry for the long post...
Don't be mistaken, I'm not on an anti-gascolator campaign...

Just trying to reason the why and how instead of blindly doing something.
For what I understand, a gascolator is a very good element to have as a water separator and filter.

My issue is that with the 10 micron uncloggable filter after the boost pump (to protect the injectors) , I don't see the use of a gascolator (with a 70 micron mesh) FWF. Not to mention that with the 8's engine mount, there is not that much space on the lower firewall...

So I understand putting 1 before the boost pump to catch the debris that went through the fuel pick-up mesh in the tank.
That means just after the selector, in the cabin. Not my preferred solution, more on this further down.
Hence my planning on putting 1 in each wing root as Bevan and others did.
But that implies increasing the complexity of the system, and I'd like to avoid that.

As for water, I can see 4 possible ways (there may be more) that it can pollute the fuel.
- Condensation in tanks (removed by draining pre-flight)
- Leaky fuel caps when parked outside in rain (removed by draining, cured by changing caps)
- Contamination while refueling (this is always a risk, of course mitigated by draining afterwards)
- Condensation in the remainder of system (IMO, this is unlikely to happen as all the system should remain primed with fuel, especially if check valves are installed)

Gascolator in the cabin:
The main (new) issue here is this heads-up I got from Robert Paisley of Protek (flyefii):
It would be best to use a positive locking drain valve on the gascolator. You don't want a push-to-open valve in the suction side of the fuel system. These can get sucked open by the pump and cause air to enter the system.

The Protek boost pump continuously delivers approx 30 GPH.

If I remember correctly, (memory tends to fade after some years... :roll eyes
on some Piper aircraft there was this drain valve that had to be ¼ turned before it was possible to push in. I assume this is what Robert is talking about.

In the cabin, with the gascolator near the floor, I believe it would be awkward to operate while catching the fuel for inspection.
Maybe I'm wrong here and over-thinking it...

On the regulatory side, I may understand where the gascolator requirement comes by reading from the Normal, Utility, Aerobatic And Commuter Category Aeroplanes:
(only (a) & (b) are relevant here...)

523.997 Fuel Strainer or Filter

There must be a fuel strainer or filter between the fuel tank outlet and the inlet of either the fuel metering device or an engine driven positive displacement pump, whichever is nearer the fuel tank outlet. This fuel strainer or filter must:

(a) Be accessible for draining and cleaning and must incorporate a screen or element which is easily removable;

(b) Have a sediment trap and drain except that it need not have a drain if the strainer or filter is easily removable for drain purposes;


The magic words here are : draining, easily removable, sediment trap, drain, drain purposes.

There doesn't seem to be a waiver for this in the Amateur-Built Aircraft chapter (549).
I didn't see any...
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