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  #1  
Old 08-04-2020, 08:06 PM
kearney kearney is offline
 
Join Date: Dec 2006
Location: Canmore, Alberta, Canada
Posts: 55
Default Gascolators, physics and Canada

Canadian builders may be pleased to learn that:

"Ottawa TCCA HQ has agreed the requirement of the exemption for a “gascolator” can be met by a device that functions OR by a system that is designed to separate water and particulate contamination from fuel. "

This means that a gascolator "device" need not be installed if the fuel system will separate water and contaminants. This is of significance for RV builders who have high pressure fuel systems.

As gascolators in RVs will always be located higher than the lowest point in the fuel system (the tank outlet), they cannot remove water from fuel (pre-flight) unless the laws of physics are repealed and water flows uphill....

Also, the filter media in gascolators is small (a few square inches) and too coarse (110+ microns)to protect injectors.

The fuel tank drain and properly sized inline filters meet the requirements and are now deemed acceptable under either the Exemption to CAR 549 or CAR 549.

For me this was quite important as most gascolators cannot withstand the fuel pressures in systems with electronic fuel injection. No can it adequately protect the injectors from sediment fouling.
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RV10 C-GCWZ Sold and now vacationing in Tulsa
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  #2  
Old 08-04-2020, 11:26 PM
Bevan Bevan is offline
 
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Location: BC
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That’s great news Les,

Can you point us to the supporting documentation in case a local inspector “hasn’t got the memo”?

May we assume this rule is retroactive for flying aircraft previously inspected?

Bevan
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Dual P-mags
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Grand Rapids EFIS
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  #3  
Old 08-05-2020, 05:46 AM
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rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
Posts: 6,094
Default

I'm certainly pleased with this as it never made sense on EFI equipped low wing aircraft. Thanks for all your work in aid of getting them to see the light.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 449.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #4  
Old 08-05-2020, 08:36 AM
kearney kearney is offline
 
Join Date: Dec 2006
Location: Canmore, Alberta, Canada
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Quote:
Originally Posted by Bevan View Post
That’s great news Les,

Can you point us to the supporting documentation in case a local inspector “hasn’t got the memo”?

May we assume this rule is retroactive for flying aircraft previously inspected?

Bevan
Bevan

The quote above came from an email I received from TC yesterday. If you run into issues with MD-RA you can use the "dispute resolution" mechanism that MD-RA was required to publish after my inspection battle with them last year. You will find it on their home page. At least now we can go to the real regulatory authority - Transport Canada.

As to previously inspected aircraft, I am not qualified to opine on what you can or cannot do.

Just for clarity, my read of what Transport Canada requires is effective filtering and the ability to separate out water. In a high wing airframe, a gascolator may be the only option if fuel freely flows from the tank outlet down the firewall to the engine.

Cheers
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RV10 C-GCWZ Sold and now vacationing in Tulsa
RV10 C-GROK Flying
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  #5  
Old 08-05-2020, 08:41 AM
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Snowflake Snowflake is offline
 
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Location: Sidney, BC, Canada
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Quote:
Originally Posted by kearney View Post
As gascolators in RVs will always be located higher than the lowest point in the fuel system (the tank outlet), they cannot remove water from fuel (pre-flight) unless the laws of physics are repealed and water flows uphill....
Unless water in the tank on a previous flight was sucked up and carried to the gascolator, where it sat until the next flight.
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  #6  
Old 08-05-2020, 01:11 PM
Ralph Inkster Ralph Inkster is offline
 
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Quote:
Originally Posted by Snowflake View Post
Unless water in the tank on a previous flight was sucked up and carried to the gascolator, where it sat until the next flight.
Which may apply for Carb and (most) Mechanical FI systems - low volume fuel flows would collect water & retain it in the gascolator to some extent, plus what ever settles out in the bottom of the tanks.

Les is not suggesting gascolators are no longer useful or required in carb or mechanical fuel injection installations. He is just noting that TC now acknowledges that gascolators can be exempted if it is not workable in installations like EFI, as long as provisions are in place to purge water accumulated in the lowest location (tanks).

With Hi Volume / Hi Pressure full return EFI systems, the best pre-flight procedure would be to check for water accumulation at the tank drains. Later, as soon as the fuel pump is engaged, whatever small water accumulations in the system plumbing would immediately be purged back into the tank, diluted harmlessly in the (hopefully) many gallons of fuel there.

As a side note & yet to be tested, it's questionable how much water would be retained in a gascolator when continually subjected to a High Volume Full Flowing fuel stream, if the turbulent flow through the gascolator might mix & syphon what ever water was in the bowl and carry it back to the tank anyway.
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  #7  
Old 08-05-2020, 02:24 PM
kearney kearney is offline
 
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Location: Canmore, Alberta, Canada
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Quote:
Originally Posted by Ralph Inkster View Post
Which may apply for Carb and (most) Mechanical FI systems - low volume fuel flows would collect water & retain it in the gascolator to some extent, plus what ever settles out in the bottom of the tanks.

Les is not suggesting gascolators are no longer useful or required in carb or mechanical fuel injection installations. He is just noting that TC now acknowledges that gascolators can be exempted if it is not workable in installations like EFI, as long as provisions are in place to purge water accumulated in the lowest location (tanks).

With Hi Volume / Hi Pressure full return EFI systems, the best pre-flight procedure would be to check for water accumulation at the tank drains. Later, as soon as the fuel pump is engaged, whatever small water accumulations in the system plumbing would immediately be purged back into the tank, diluted harmlessly in the (hopefully) many gallons of fuel there.

As a side note & yet to be tested, it's questionable how much water would be retained in a gascolator when continually subjected to a High Volume Full Flowing fuel stream, if the turbulent flow through the gascolator might mix & syphon what ever water was in the bowl and carry it back to the tank anyway.
Ralph - Exactly!!

By the way, I did the science on gascolator operation last weekend. I mixed 1 gal of avgas and a couple of cups of water. Shook it up and then ran it through an ACS "high pressure" gascolator. After running the full gal through the gascolator, it retained only a small amount of water. I repeated the experiment after letting the water settle out - same result. In any event, a gascolator holds only a trivial amount of water. The closed loop fuel system means any water is swept back into the tank and is mixed with fuel. It is not meant to be a gas/water fuel separator IMHO.
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  #8  
Old 08-05-2020, 04:23 PM
Bevan Bevan is offline
 
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Ralph, I would like to know more details about how you did the test. Flow rate through gascolator is my main question. What type of gascolator (filter material) was used. For example, I use Andair gascolators which have a 75micron filter element which I believe is to help strip off the water. I would think flow rate has a lot to do with the success of that.

If the water is shaken up with the fuel as you say, then immediately put (pumped?) through a line to the gascolator, I can could see why the water may not seperate out. But is this a realistic scenario?. What we’re trying to avoid is a slug of water in the bottom of the tank making it’s way to the engine. The volume of the gascolator is to allow the water to seperate out as it passes through. The filter material helps to. All in theory anyway as I understand it.

Bevan
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RV7A Flying since 2015
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 : 08-05-2020 at 04:25 PM. Reason: Added a word for clarity.
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  #9  
Old 08-05-2020, 05:44 PM
kearney kearney is offline
 
Join Date: Dec 2006
Location: Canmore, Alberta, Canada
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Quote:
Originally Posted by Bevan View Post
Ralph, I would like to know more details about how you did the test. Flow rate through gascolator is my main question. What type of gascolator (filter material) was used. For example, I use Andair gascolators which have a 75micron filter element which I believe is to help strip off the water. I would think flow rate has a lot to do with the success of that.

If the water is shaken up with the fuel as you say, then immediately put (pumped?) through a line to the gascolator, I can could see why the water may not seperate out. But is this a realistic scenario?. What we’re trying to avoid is a slug of water in the bottom of the tank making it’s way to the engine. The volume of the gascolator is to allow the water to separate out as it passes through. The filter material helps to. All in theory anyway as I understand it.

Bevan
Hi Bevan

So there were two tests at about 34 GPH. The first had fuel mixed with water and shaken (not stirred per JB!). This simulated getting a partial tank of contaminated fuel. The second test allowed fuel to sit for 30 minutes and the water to settle out.

In both cases the gascolator collected minimal water. The filter media was about 6-7 square inches and 110_ microns. If you google fuel/water separators they have filters that are under 10 microns.

Gascolators are not fuel / water separators. What they do do is allow water to collect and be detected when located in the lowest part of the fuel system. They serve no purpose other than a fuel filter when installed in a low wing aircraft such as an RV. In my PA28 that I flew for 19 years, I only detected water when draining the tank and never in the FWF gascolator.

PS: Where are you located? I am in Springbank. We should meet sometime and swap lies.
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RV10 C-GCWZ Sold and now vacationing in Tulsa
RV10 C-GROK Flying
RV10 # 3 - under construction

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  #10  
Old 08-05-2020, 07:29 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Bevan View Post
What we’re trying to avoid is a slug of water in the bottom of the tank making it’s way to the engine.

Bevan
Draining the tanks before flight would eliminate this possibility.

With EFI systems and the high return fuel flow (99% return at idle), any water in the system is completely mixed with the fuel within a few minutes. 35-40 gph are typical pumping rates with these systems.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 449.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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