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MD-RA Inspection Services Fuel System Requirements

kearney

kearney

Well Known Member
Hi

Attached is a TCCA Advisory Circular dealing with fuel system & amateur built aircraft. It codifies the old C52E Fuel Systems into an advisory circular. I am told that MD-RA Inspector training will be updated to reflect this document. Hopefully it will eliminate much of the angst builders have had regarding fuel systems.

Of particular note is that it formally states gascolators / fuel strainers are not mandatory.
 

Attachments

  • AC 549-001 - ISSUE 01 - AMATEUR-BUILT AIRCRAFT FUEL SYSTEMS.pdf
    187 KB · Views: 102
In particular, if you're not using a Gascolator:

4.6 Gascolator alternatives
(1) In some aircraft designs, installation of a ‘gascolator’ as a unit may not be possible or practical.
(2) Other means of achieving the necessary capabilities of the Fuel Strainer or Filter Assembly may
be employed if, for reasons of practicality, the builder chooses to develop an alternate design that
performs the same functions and meets the intent of this guidance.
(3) The builder of the aircraft should be prepared to demonstrate that whatever means are employed,
an adequate supply of filtered fuel, free of water and sediment, to the engine is assured, and that
there are sumps and drains that will allow the capture, detection, and removal of contaminated
fuel prior to flight, with reasonable ease.
(4) Readily accessible and serviceable in-line filters of sufficient capacity, together with separate
water drains at low points, may be employed.
(5) Paper filter elements are not acceptable, unless they are rated by their manufacturer for airborne
aviation fuel use.
Click to expand...
 
Thanks for posting this Les and being tenacious in getting them to move on this.

Keith
 
Seems to me a gascolator remains the easiest way to meet the intent...
And the requirement to be "accessable" precludes the wing root location some use
 
Mike, the RV10 and 14 werent designed for the use of gascolators. The 7, 8, 9 were. Because there is a tunnel, it means a fairly significant modification.

Tom
 
mvs163 said:
Seems to me a gascolator remains the easiest way to meet the intent...
And the requirement to be "accessable" precludes the wing root location some use
Click to expand...

Most of the affected aircraft in Canada are EFI equipped.

Gascolators are not the most compatible setup for EFI engines operating at 50ish psi. The screen is generally too large to adequately protect the pumps and injectors (70-120 micron is common). We recommend 35-40 micron.

Water passes through the larger mesh at these pressures and very high fuel flow rates too. As such, we've never recommended gascolators with our systems as they don't serve much of a purpose here and many not designed for these pressures.

Our recommendation is to pre-flight sample at the lowest points, which are the tank drains on RVs and use proper high pressure, serviceable filter's designed for the task. Follow our recommended service intervals and cautions.

SDS will pass 1 million flight hours collectively in 2024. Haven't had a single report from the field where water in the fuel has caused any running problems with the recommended fuel system and procedures.

Components used on carbed engines may not be suitable with EFI. It's a different beast.
 
mvs163 said:
Seems to me a gascolator remains the easiest way to meet the intent...
And the requirement to be "accessable" precludes the wing root location some use
Click to expand...
Gascolator. I concur with the idea that it meets intent easily.
Accessible as in to sump fuel pre-flight? No different from sumping the tanks or the firewall mounted. Seconds to do.
In order to inspect the screen filter? Taking the lower wing root cover off during your annual, also not too a big job.
Taking the seats and seat pans out to inspect the aileron pushrods etc during annual. That is a big job. :)
 
mvs163 said:
Seems to me a gascolator remains the easiest way to meet the intent...
And the requirement to be "accessable" precludes the wing root location some use
Click to expand...
No less accessible than the firewall. I have to drop my lower cowl to service mine, if I had one in each wing root i'd have to pull the wing root fairings to service them. Once that was done, servicing would be the same.

Preflight checks wouldn't be any harder either, you have to reach the back corner of the tank anyway to drain fuel to check it, the gascolator drain would be right there beside it.

Is there some other servicing difficulty you had in mind with the wing root location?
 
Snowflake said:
In particular, if you're not using a Gascolator:
Click to expand...
Should be interesting to see how readilly accessable is interpreted...
As RV rs we tend to think we're the centre of the universe but I seem to recall other companies, Zenair I think, supplying a small container that has a quick drain at the lowest part of the system that could be drained easily.
I have a very nice piece from Flyboys Accessories in my latest RV located in the belly that does what a gascolator does. It can be drained and the filter can be removed without draining the fuel or having extra fuel shutoff valves in place.
I don't like gascolators on the lower firewall for fire reasons...
Wipe the gear off and the gascolator is the next thing to hit the ground.
Modern aircraft companies like Diamond find ways to protect the gascolator in the event of a crash.

I'm just not getting the gascolator fight logic...
Carry on
 
Jetmart said:
Ross are you saying most aircraft in Canada are fuel injected or specifically EFI?
This surprises me.
Click to expand...

I am saying that most of the builders having issues with MDRA and the fuel system failing inspection have been EFI equipped.
 
mvs163 said:
So no 10s or 14s have gascolators ?
Click to expand...

AFAIK, gascolators are not required in the US or most other countries, only Canada. That may tell you something. Do we see more fuel/ water related accidents in aircraft outside Canada?

This is just dogma which doesn't hold up in a technical discussion regarding EFI differences from carbs and mechanical FI.

As far as servicing/ inspection, takes not much longer to remove the wing root fairings as removing the lower cowling.
 
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Mike---not as originally specified by Vans. Not in the plans, nor a provision for one. All the engines specified for the 2 models were injected.

Tom
 
Rob---its more the vertical height of the gascolator, as least from our plumbing perspective. Our theory for the root filters was a redundant backup by filtering each tank. This eliminated that part of the single filter blockage potential. Yes we still have a post filter FWF to protect the injectors in case of a pump failure.
So far----after several years, we havent heard of any.

Tom
 
Gascolator Requirement

There have been several RV10's and an RV14 that have passed inspection, using only inline filters, after appeal to Transport Canada Civil Aviation. These appeals only took days. The real reason MD-RA Inspection Services does not want to approval these installs is that they perceive a liability issue on the part of inspectors.

Gascolators are 100+ year old technology that cannot, will not work as designed when installed in a low wing aircraft unless installed below the wing. They represent a significant point of failure when installed in a pressurized fuel system.

The most recent email I received from TCCA states : Please find attached the new TCCA Advisory Circular, AC 549-001, which came into effect on October 1st. This new AC will be used to further update the MD-RA Delegate training material that will be used during the next MD-RA delegates training session and MD-RA Inspection Service will be removing their MDRA C52 document from their website in the coming weeks. With the publication of AC 549-001, the discussions between amateur aircraft builders and our MD-RA delegates regarding the use of gascolators, or substitutes, should be simplified.

I suspect & hope this issue is now over and that inspectors will accept any airworthy fuel system that is fit for purpose.

If anyone has an issue with an inspection regarding this issue, PM me and I will help them through the appeal process.
 
I might add here that MDRA was often (but not always) requiring that the filters be modified with a drain. Since the filters are usually 1-2 inches higher than the wing tank drains, they serve no useful purpose in trying to sample for water there.

Water is heavier than fuel and it doesn't flow uphill. The only ways you'd get water in the fuel is through the tank first, either through condensation, a leaky cap O-ring with rain or water in the fuel when the tank is filled. You can sample for this water at the tank drain provided.

The whole filter drain requirement was illogical. MDRA/ TCCA wasn't interested in any technical discussion on the matter.
 
GOFT said:
Taking the seats and seat pans out to inspect the aileron pushrods etc during annual. That is a big job. :)
Click to expand...

Funny, that's exactly what I did yesterday and the day before, along with the aft of baggage wall inspection. Not an easy job for a big guy who doesn't bend and contort like he did in his youth.

Front of firewall gascolators aren't that bad to inspect on a 9, that's on my list for the next week or so.

Annuals, so much fun.
 
kearney said:
Gascolators are 100+ year old technology that cannot, will not work as designed when installed in a low wing aircraft unless installed below the wing.
Click to expand...
Nonsense. In a low-wing aircraft fuel has to flow uphill to the engine from the pickup in the tank, yes. A gascolator placed anywhere along that slope will trap any water that gets to that point on the slope. The gascolator doesn't know if it's above, below, or beside a fuel tank, just what comes in the inlet and what goes out the outlet...
 
mvs163 said:
I don't like gascolators on the lower firewall for fire reasons...
Wipe the gear off and the gascolator is the next thing to hit the ground.
Click to expand...
Only if the gascolator sticks out of the fuselage. Mine is fully inside the lower cowl, I preflight it by popping a 1-1/8" hole plug out of the cowl and pushing a fuel test tube up to the drain... It works great.
 
Snowflake said:
Nonsense. In a low-wing aircraft fuel has to flow uphill to the engine from the pickup in the tank, yes. A gascolator placed anywhere along that slope will trap any water that gets to that point on the slope. The gascolator doesn't know if it's above, below, or beside a fuel tank, just what comes in the inlet and what goes out the outlet...
Click to expand...

I believe Les was talking about EFI installations here as that is the focus of all this work. Gascolators don't trap much water at 45 psi. We know, we tested it on a rig.

The idea is to drain any water that may be in the tanks, pre-flight. Easily done with the Van's provided quick drains.

The other difference with EFI is the high fuel return rates. Any water remaining in the system is simply mixed up with the fuel and goes through the engine in small, homogeneous quantities. Causes no running issues.
 
Lets try a thought experiment.

Assume I fly to Kosh land and tie down. Assume the standard KOSH monsoon occurs and I get a **** ton of water through a leaking gas caps.

Scenario # 1.

If I sample my gascolator first, I will draw water from the tank into one of the fuel lines (there is no "both" on the fuel selector valve"). I will see no water in the gascolator sample (unless I draw a ton of water from the tank to the gascolator and them the whole fuel line is contaminated).

If I then sump the tank drains, I will remove all the water in the tanks but the water in the fuel line from one of the tanks s will remain contaminated.

If I have a Airflow Performance injection system I will need to run all the water though the engine before it starts.

Scenario # 2. Same as above but I change fuel tanks before I start engine. In this case no water was drawn into the engine and everything is normal. However, if I change tanks again in flight, the slug of water in the fuel lines will enter the engine. The engine will stop making power until all the water is processed through the engine.

Scenario # 3. Same as above except I have a duplex fuel valve and a return line to the fuel tank. As before I drain gascolator then sump tanks.

As soon as the fuel pump is started (before startup), any contaminated fuel in the lines and/or gascolator will be swept back to the fuel tank and mixed with the fuel. It will be a trivial event.

If the contaminated fuel line is selected in flight, the same thing happens. It is unlikely that it will be even noticed.

Scenario # 4.

Same as above but there is no gascolator. When tanks are sumped, all water is removed. There is no water in fuel lines as water does not travel uphill unless fuel is being circulated. No impact on startup or flight with either mechanical or electronic injection.

Other Info

I did a bench test with a gascolator and a known amount of contaminated fuel. A gascolator does not separate water from fuel - the percentage of water in the fuel matched the percentage in the "tank".

Further, after introducing water in the tank, no water made it to the gascolator, before circulating fuel, as the gascolator inlet was higher than the tank outlet. Water does not run uphill.

Conculsions

A gascolator in a mechanical injection system makes the risks associated with water contamination worse not better. Unless fuel is moving, the gascolator will never see water in the fuel tank.

Gascolators serve no purpose in low wing aircraft.

Please tell me where my logic is flawed.
 
kearney said:
Scenario # 1.

If I sample my gascolator first, I will draw water from the tank into one of the fuel lines.
Click to expand...
Correct. Which is why you'd never sample the gascolator first. Always sample the source first, ie. the tanks. I don't know why this would even come up.

Scenario # 2. Same as above...
Click to expand...
Same answer.

Scenario # 3. Same as above except I have a duplex fuel valve and a return line to the fuel tank. As before I drain gascolator then sump tanks.
Click to expand...
Same answer.

Scenario # 4.

Same as above but there is no gascolator. When tanks are sumped, all water is removed. There is no water in fuel lines as water does not travel uphill unless fuel is being circulated. No impact on startup or flight with either mechanical or electronic injection.
Click to expand...
Yes, this is correct.

Other Info

I did a bench test with a gascolator and a known amount of contaminated fuel. A gascolator does not separate water from fuel - the percentage of water in the fuel matched the percentage in the "tank".
Click to expand...
Was this on a high-pressure injected system, or a carbureted system?

Please tell me where my logic is flawed.
Click to expand...
See above.
 
Snowflake said:
Correct. Which is why you'd never sample the gascolator first. Always sample the source first, i.e. the tanks. I don't know why this would even come up.
Click to expand...

I agree, test source first - the tanks. If I remove all water from the tanks, how does water get into the gascolator mounted on the firewall?

I parked a PA28 outside form 19 years. I never found water in the gascolator. I often found water in the tanks (PA-28 gas caps would leak).

Water will never, ever get into a gascolator on a low wing aircraft if the water is removed from the tanks first.

As for my bench test, I was circulating fuel with a high pressure electric pump. I wanted to see if water would separate out of the circulating.

What value does a firewall mounted gascolator provide?
 
kearney said:
I agree, test source first - the tanks. If I remove all water from the tanks, how does water get into the gascolator mounted on the firewall?
Click to expand...
It doesn't... If you get it all. Did you forget to rock the wings and wait for water to run down to the drain first? Was there enough water there that your fuel test tube filled completely, and you mistook that for a full tube of gas? There are lots of reasons you *don't* get all the water out of the tanks even when sumping them first.

I parked a PA28 outside form 19 years. I never found water in the gascolator. I often found water in the tanks (PA-28 gas caps would leak).

Water will never, ever get into a gascolator on a low wing aircraft if the water is removed from the tanks first.
Click to expand...
I flew a hangared wooden homebuilt for a few years, that occasionally did have water in the gascolator. It also had a behind-the-firewall gas tank with a vent/pressure tube that pointed forwards in to the airstream, perfect for picking up water if you flew through some rain. It was a low wing aircraft... So... never say never. Further, you could drain the water from the tank, drain the water from the gascolator, go fly through rain, and afterwards drain water from the gascolator.

rv6ejguy said:
As I have stated several times in this thread, we are talking about EFI systems operating at around 50 psi here, not carbs.
Click to expand...
Les keeps using blanket statements like "all low wing aircraft" and talking about PA-28's which don't have EFI, so not everyone is talking only about EFI.
 
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Snowflake said:
Les keeps using blanket statements like "all low wing aircraft" and talking about PA-28's which don't have EFI, so not everyone is talking only about EFI.
Click to expand...

In the context of MDRA inspections related to failing inspections where no drains were installed on filters, 100% have been EFI projects to my knowledge.
 
Snowflake said:
It doesn't... If you get it all. Did you forget to rock the wings and wait for water to run down to the drain first? Was there enough water there that your fuel test tube filled completely, and you mistook that for a full tube of gas? There are lots of reasons you *don't* get all the water out of the tanks even when sumping them first.

Les keeps using blanket statements like "all low wing aircraft" and talking about PA-28's which don't have EFI, so not everyone is talking only about EFI.
Click to expand...
Okay my bad - I'll be specific. I'll stick with low wing aircraft like Van's design, with fuel injection.

In my opinion, a firewall mounted gascolator is not only useless but dangerous. If it leaks you risk a FWF fire. Also, in the case where you don't get all the water out of your tanks, it will not detect the remaining water unless you draw water from the tanks to the gascolator and then out the gascolator. Water will not get to the gascolator unless fuel is moving.

Therefore, a gascolator is not a substitute for properly sumping tanks.

Further, if the water is only in one tank and the selector is on the other tank, even drawing fuel from the tank to the gascolator and out the gascolator doesn't help as the gascolator only "sees" the uncontaminated tank.

A gascolator will not tell me if I have introduced water into my tank before flight. If the gascolator tells me there is water in my fuel after a flight then it is telling me the water was not sufficient to be hazardous. Of course if the amount of water was hazardous during a flight, that might be of interest to the NTSNB / TSB accident investigators.

Gascolators use drains sealed using O-Rings. IF I get a leaky O-Ring I will get air in my fuel lines (it is on suction side) or spray fuel (it is on the pressure side). Why risk either scenario when a gascolator provides no value.

Lastly, when I bench tested a gascolator - a closed loop test with an electric fuel pump moving 50 GPH, I found the percentage of water / fuel in the gascolator matched the percentage in the fuel. The gascolator did not strip water out of the fuel.
 
kearney said:
Okay my bad - I'll be specific. I'll stick with low wing aircraft like Van's design, with fuel injection….

….Lastly, when I bench tested a gascolator - a closed loop test with an electric fuel pump moving 50 GPH, I found the percentage of water / fuel in the gascolator matched the percentage in the fuel. The gascolator did not strip water out of the fuel.
Click to expand...

Les, considering that this website and thread is geared towards RVs and the majority of fuel injected RVs use mechanical injection (with no return line) at lower pressures and fuel flows than EFI, would you say that a gascolator (with an internal filter which I thought was there for the purpose of stripping fuel) would not strip fuel any significant amount of water from the fuel at the much slower flow rate of 8gph when mounted on the suction side of the fuel system?

Bevan
 
Bevan said:
Les, considering that this website and thread is geared towards RVs and the majority of fuel injected RVs use mechanical injection (with no return line) at lower pressures and fuel flows than EFI, would you say that a gascolator (with an internal filter which I thought was there for the purpose of stripping fuel) would not strip fuel any significant amount of water from the fuel at the much slower flow rate of 8gph when mounted on the suction side of the fuel system?

Bevan
Click to expand...

Bevan

The key question, in my mind, is what is the purpose of the gascolator. In the installations we have been discussing, it won't detect water in fuel before flight. If it is to remove water in flight, that is a different purpose - one for which I have found no data. The screen won't separate water from fuel - it is far to course for that purpose. If it is to separate water inflight, how does it accomplish this? Perhaps others smarter than me can explain the physics...
 
Not a water seperator

To my understanding, a gascolator acts primarily as a gravity collector for water and small particles of sediment and relies mostly on dwell time to fulfill its function.
They are considered functional for gravity feed, low fuel flow systems such as found on high wing aircraft.

A gascolator is not meant to be a water/fuel separator when fuel is flowing through. (though one might test this at 8 - 15 GPH?)
Even less so when the fuel flow is driven through it at 50ish GPH such as when a EFI system demands it, and that was demonstrated.
To this day, the MDRA do not seem to appreciate the different particularities of a EFI system and insists on applying their interpretation of TC's requirements on a widespread basis.
 
riseric said:
To this day, the MDRA do not seem to appreciate the different particularities of a EFI system and insists on applying their interpretation of TC's requirements on a widespread basis.
Click to expand...

That's it in a nutshell. The gascolator serves no useful purpose with regards to trapping water on EFI equipped installations and drains on filters not located at the lowest points of the system also serve no useful purpose for draining water, pre-flight.
 
Bevan said:
Les, considering that this website and thread is geared towards RVs and the majority of fuel injected RVs use mechanical injection (with no return line) at lower pressures and fuel flows than EFI, would you say that a gascolator (with an internal filter which I thought was there for the purpose of stripping fuel) would not strip fuel any significant amount of water from the fuel at the much slower flow rate of 8gph when mounted on the suction side of the fuel system?
Click to expand...
There is at least anecdotal evidence that it works in low-flow systems such as those driving a carbureted engine, as it should.
 
kearney said:
I prefer verifiable data. Anecdotal "evidence" is subject to confirmation bias.
Click to expand...

Drain tank before flight.
Drain gascolator before flight.
Fly in known rain conditions.
Land, find water in gascolator.

Only opening to the fuel system was on the vent tube on the fuel cap.

Do you have any *other* suggestions where the water could come from?
 
Snowflake said:
Drain tank before flight.
Drain gascolator before flight.
Fly in known rain conditions.
Land, find water in gascolator.

Only opening to the fuel system was on the vent tube on the fuel cap.

Do you have any *other* suggestions where the water could come from?
Click to expand...

Interesting and food for thought, but not EFI equipped.
 
Snowflake said:
Drain tank before flight.
Drain gascolator before flight.
Fly in known rain conditions.
Land, find water in gascolator.

Only opening to the fuel system was on the vent tube on the fuel cap.

Do you have any *other* suggestions where the water could come from?
Click to expand...
The question as to where the water came from is a red herring. I would certainly agree it came from the tank given the specifics you state.

What was not demonstrated was whether or not the gascolator worked. By this I mean did it separate and retain water from the fuel in a greater concentration than found in the circulating fuel. In my bench tests I found that the % water in the gascolator never exceeded the percentage in the circulating fuel.
 
Canadian Fuel Drain Update

We've received no useful responses to our concerns and questions about this topic from TCCA, despite numerous Email exchanges. They've ignored and refused to have any reasonable technical discussion on the matter.

We'll soon be updating our SB page with a Safety Bulletin, the gist of it being we that don't approve modifications to our fuel filters with drain fittings. We don't want to be held responsible when unapproved fuel drains, not designed for high pressure fuel systems are installed.

We consider them a possible hazard on the inlet side if air is introduced on the inlet side of the pump and a possible fire hazard FWF when fitted to the high pressure filter.

These cannot serve the purported function that MDRA and TCCA assert in the locations typically possible on RVs.

Les Kearney has done testing on the factory tank quick drains and these are highly effective in eliminating water from the fuel system pre-flight. IMO that's all that's needed here and that's working just fine on EFI RVs in the rest of the world as we approach 1 millions flight hours in 2024. TCCA doesn't care about facts, they intend to shove this down our throats.

I'll be publishing some of the correspondence we've had with TCCA early next year as time permits so you can see what has transpired over the last 4 years on this topic.

This unfortunately leaves Canadian builders trapped between us and MDRA/ TCCA. If you want to fly EFI you may have to install the drains and assume responsibility jointly with TCCA if anything happens. We won't be on the hook for this. Unfortunate it's come to that. We tried our best to reason with the powers that be.
 
I was researching gascolaters this morning and found this. Based on my experience as an A&P, I think I see a lot of misinformation here. For example -

1. They don't work on low wing aircraft - Where does this thinking come from? Obviously they can catch water and dirt on the way from the tanks to the pumps. They're not there to be the lowest point in the system i.e. below the tanks and etc. But they will catch stuff along the way, speaking from experience emptying them. Water is separated by gravity, not the screen in the gascolater as Kearney claimed. The reservoir provides a place for water to collect while the screen filters out large particles. If the fuel system needs further filtering, that must be provided by a filter/screen down the line typically found in the carburetor or injection system (typically two more screens before the injectors).

2. 50psi in the gascolater..Where does this come from? I've always seen the gascolater before the engine pump, not after. I've never seen an installation where it's subjected to pressure. Why would anyone do that in a light airplane? That sounds like trouble to me. Why? Because pumps typically have check valves and a small piece of pro-seal, rubber, whatever can keep it from working. I've seen this in NTSB reports.

3. Won't work/not needed with EFI.. What's fuel injection got to do with this? Lots of low wing production aircraft have gascolaters..Cirrus for example. Are we saying the engineers at Cirrus don't know what they're doing with over 9000 aircraft delivered?

4. Draining the tanks will get all the water out of the system.. Totally not true. Water gets trapped in seams, pockets, bulges, whatever in tanks and in low places in fuel lines and valves. Then in flight, motion moves the water around. Numerous crashes in Cessnas for example have been caused by this problem driven primarily by leaky fuel caps. Yes they're not RVs but the principle is the same and the RV caps are similar in design to the Cessna Shaw and Wisco caps. If you want to prove it to yourself, add a known amount of water to one of your tanks and then try to drain it all out at the sumps (as the NTSB has demonstrated). Don't forget, water gets in by condensation as well and you can have condensed water drops clinging to the top surface of the tank which won't get into the gas until the gas is sloshed around.

5. Gascolaters provide no value - Doing aircraft mx I find sediment, pieces of rubber, pro-seal, paint chips, and water in gascolater bowls as well as in carburetor bowls. They obviously work or they'd never have anything in them.

6. Gascolaters increase risk by possible failure of the o-ring/leakage etc. Certainly possible. But high quality units (Steve's for example) minimize this risk, seal tightly, and protect the o-ring. They're also metal and crashworthy. But aviation is all about management of risks. The gascolater does trap crap and water to some extent and that's a fact verified by cleaning them out. That provides a benefit. Does that benefit outweigh the very small risk? That's up to you. Obviously Cirrus, Robinson Helicopter, and others believe so. Maybe they're wrong..
 
Trimetric - Welcome
Based on your experience with conventional, I am meaning fuel systems used in certified aircraft, your thoughts are valid.
The situation that prompted this discussion involves a fuel system that is similar to a modern automotive fuel injection system. The fuel after the fuel pump (usually in the foot well) is brought up to 40 to 50 psi with a hi pressure/hi volume pump and maintains that up to all the electronic fuel injectors at each intake port and what isn’t used in the engine is released through a pressure relief valve & flows back into the tank. These systems are flowing at more than 30 gph, so up to 2/3 of the fuel flowing through the system returns to the tank.
The issues discussed here is that Transport Canada and it’s delegate inspection service MD-RA can’t or won’t adapt to the circumstances created in this newer type of fuel delivery system. Gascolators are prone to leaking at these high operating pressures and the moment these hi volume fuel pumps are activated, any functional value of water collection a gascolator may have are flushed away.
Yes, gascolators have a purpose in conventional fuel systems, with one way fuel flow, but in a full circulating flow situation, it doesn’t make sense as long as there is provision to drain fuel samples from the lowest spot ( & on a RV, that is the tank).
For studying full flow EFI systems, refer to Racetech SDS or EFII System 32 installation manuals as they are the 2 only suppliers of these systems, other than a few builder custom examples.
 
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Ralph Inkster said:
The issues discussed here is that Transport Canada and it’s delegate inspection service MD-RA can’t or won’t adapt to the circumstances created in this newer type of fuel delivery system. Gascolators are prone to leaking at these high operating pressures and the moment these hi volume fuel pumps are activated, any functional value of water collection a gascolator may have are flushed away.
Click to expand...
I think Trimetric's point was that the Gascolator (or gascolators) could be on the suction side of the pump, at lower pressure.
 
Snowflake said:
I think Trimetric's point was that the Gascolator (or gascolators) could be on the suction side of the pump, at lower pressur
Click to expand...
Full flow fuel systems would or should have in line filters both sides of the fuel pump, so crap in the line issues should be covered.
Water entrapment in the lines after the pump are flushed the instant the fuel pump is activated.
Drains in the lowest point prior to the pump should be used to address water issues, if you must, a gascolator near the fuel pickup would suffice - but the instant the pump is activated, that water in that gascolator would be sucked in & thru the circulated flow.
Again.. drain water out from lowest point before initiating pump.
 
Snowflake said:
I think Trimetric's point was that the Gascolator (or gascolators) could be on the suction side of the pump, at lower pressure.
Click to expand...
Has anyone measured what's the "succion" value prior the fuel pump?
Mine has a measured flow of ~200 litres/ hour, that's ~50 gallons/hour.
With a Gascolator before the pump, I would be worried that the Gascolator's drain spring give ever so slightly in that "succion" and let air in.
And it would still not seperate water from fuel when flowing at that rate.
The main issue here is not disputing a Gascolator's role in gravity fed fuel systems or low pressure/flow fuel systems, but the fact that MD-RA's reps won't acknowledge that in a high pressure/flow recirculating system, a Gascolator can't/won't function as designed.
 
It was mentioned earlier in this thread but some may have missed it…
A gascolator will not separate water from fuel at higher system pressures and flow rates that are common in modern fuel injection systems.
This was tested and confirmed when the Rotax 912iS redesign was being engineered for the RV-12iS. That is why it has no gascolator.
 
Hi Trimetric - welcome to the zoo!

i will respond to your post and points and comments in order. First off though I will set out a few key data Points.

a. We are talking about electronic fuel injection systems in RV type aircraft systems
b. In the RV10 there is a continuous flow of 40-50 geh to the engine of which 30+ is returned to the originating tank via a duplex fuel valve.
c, The system uses electric fuel pumps located before the engine. There is no mechanical pump.
d. In-line filters with 40 micron filter media are used. Gascolators typically use 80-100 micron media.
e, I have never claimed gascolator screens separate water. If something I wrote implies that it was a mistake.
f. Transport Canada explicitly requires gascolators to be located at the lowest point of the fuel system. Fortunately this is. It enforced

Responding to your points

1. The point of a gascolator is to remove water before flight- not during flight. water will not migrate uphill.. Therefore it will not function as designed in a low wing aircraft when located above thefueltankoutlet.

2. The fuel pressure in these systems is 45-50 psi driven by dual electric fuel pumps.

3. TheCirrus uses MECHANICAL fuel injection not electronic.

4. I have done exactly as you suggest. The trivial amount of what left after draining was not a risk to safe flight. I have demonstrated that as well. I have video proof demonstrating this. In short, the tank drains are 100% effectivein removing water.

5. When i line filters are installed,the gascolator screen is not required. As the gascolators screen is smaller it is less tolerant to contamination that in line filters with a larger media surface area.

6. Risk management suggests that installing a device is an environment for which it was not designed, in which it adds no incremental value is not prudent.
 
I’d like to add another data point to this discussion,

Last year I mixed some water in gas and ran the mixture through a gascolator. The percentage of water in the gascolator matched the percentage in the source. This demonstrates that the gascolator does not remove water from fuel.

i have yet to hear anyone provide an explanation as to how a gascolator strips water from fuel. I do agree that whatever water is in the gascolator when the flow stops will settle as it will in the fuel tank.
 
kearney said:
I’d like to add another data point to this discussion,

Last year I mixed some water in gas and ran the mixture through a gascolator. The percentage of water in the gascolator matched the percentage in the source. This demonstrates that the gascolator does not remove water from fuel.
Click to expand...
Wouldn’t this mean that the gascolator did remove the water? (Or maybe I am not understanding what you meant to say)

A gascolator actually will separate water from fuel if the flow rate is low enough. That is one of the reasons they were commonly incorporated into aircraft fuel systems. They just can’t do it on a high pressure / high volume flow.
 
rvbuilder2002 said:
Wouldn’t this mean that the gascolator did remove the water? (Or maybe I am not understanding what you meant to say)

A gascolator actually will separate water from fuel if the flow rate is low enough. That is one of the reasons they were commonly incorporated into aircraft fuel systems. They just can’t do it on a high pressure / high volume flow.
Click to expand...
In my test the proportion of the water in the gascolator matched water in source container. In other words the gascolator did not separate any additional water. I suspect the flow rate would have to be quite slow to allow water to settle out but I have no empirical data in that regard.

in any event, the purpose of a gascolator is to allow detection of water BEFORE flight. How would water get into the gascolator before flight if it is higher than the tank outlet. That is the question that Recreational Aviation Services Inc will not answer (They control MD-RA inspectors).
 
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