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Gascolator locations

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dan(at)syz.com
Guest

Posted: Wed Jun 10, 2015 12:50 pm Post subject: Gascolator locations

Hi everyone.



I'm in Canada, and stuck with an obsolete regulation that we require gascolators in homebuilt planes.  Though they're pretty much pointless in a low-wing fuel injected plane like the RV-10, I have no choice but to put one in.  I've done as much research as I can in trying to decide exactly where would be the "best" place to do so, but wanted to post my observations and thoughts here in case anyone can find something I've overlooked, or can assuage any of the potential pitfalls I see in different scenarios due to your own experience.  No matter where I install it, the specific gascolator I am considering is the Andair GAS375 - as it seems to be one of the better constructed.



I see three locations where they can be installed - in the wing roots, in the tunnel, or on the firewall.



Firewall:  Advantage - relatively straightforward to install there.  Disadvantages - If an O-ring or something starts to leak, it would spray fuel around the engine compartment under pressure (are potential leaks of this sort a real possibility to consider?).  That can't be a good thing.  Also, under the hot cowling, would it cause an increased potential for vapour lock?  It may also not be the true "lowest" point in the fuel system, which the regulations also specify.



Tunnel:  Two options here - adding it as another device in the tunnel, or replacing the fuel filter already there with the gascolator.  On first glance, replacing the fuel filter seems to be the way to go since the addition of the gascolator wouldn't be adding a new point of failure - just replacing one.  Though when I checked with Van's about this, they recommended against it - they would rather see the recommended filter still in place, and the gascolator added elsewhere.  In any case, whether adding the gascolator on its own, or replacing the existing filter, an advantage would be that it should be less likely to contribute to vapour lock, provided that tunnel heat isn't excessive.  Disadvantages - there is still the possibility of spraying fuel under pressure if it were to fail, and in the tunnel seems just as bad (if not worse) than the engine compartment.  Secondly, the fuel drain for the gascolator would be in the vicinity of the exhaust pipes.  I've had first-hand experience with fuel tank drains leaking and dribbling due to debris that ended up getting into the seal.  If it were to dribble fuel into the hot exhaust gases, again that can't be a good thing.



Wing roots:  Advantage - they'd be cool out there so wouldn't contribute to vapour lock.  Also, if they started leaking (either through O-rings failing or the drain dribbling), it's less of an issue.  Plus, since there would have to be two, if one did start to leak in a spectacular fashion, there is the redundancy of two, so at least the fuel in one of the wings would stick around.  And they wouldn't be pressurized there, so leaks should be less dramatic.  Disadvantages - Cost would be twice as much, since two would be needed.  There would be no way to shut off the fuel prior to the gascolators for cleaning the filter, so the tanks would have to be drained to do so (I wouldn't want to introduce yet another point of failure by installing shutoff valves before them)  Also, the gascolator would have fuel sucked through it rather than pushed through it, so it would be under a small amount of negative pressure rather than positive pressure (more so when the filter starts to get dirty) - would this cause potential problems with air possibly be introduced through the drain port?  Or is the seal and spring on the drain port more than strong enough to maintain a seal against the outside even when being sucked up with the negative pressure?



I hate having to install a gascolator in the first place, and it doesn't help to have not come up with a clear winner with regards to location.  Any advice anybody could give would be greatly appreciated.  Am I overlooking anything, or equally, overstating the likelihood of certain failure scenarios?



Thanks!



Dan

---

Dan Charrois

President, Syzygy Research & Technology

Phone: 780-961-2213

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carl.froehlich(at)verizon
Guest

Posted: Wed Jun 10, 2015 1:51 pm Post subject: Gascolator locations

Before I understood gascolators I put an Andair gascolator on my first

plane, an RV-8A with an IO-360 engine.  I mounted it using a piece of angle

on the lower left corner of the firewall such that a push drain valve

(identical to the ones on the wing tanks) on the bottom of the gascolator

could be accessed with the cowl on (the cowl had a 1/2" hole for this

purpose).  The angle held the gascolator off the firewall enough such that

the drain valve was forward of the lower cowl attach hinge.  The bottom of

the drain valve was just inside the cowl so a standard sump glass with a

sump rod could sump the gascolator.  12 years of flying and I never had an

issue or a problem with vapor lock.



Two other recommendations:

- plumb the fuel system with the inline filter in the tunnel per plans.

While the filter in the Andair gascolator meets the specs for the fuel

system, it is after the fuel pump and small compared to the inline fuel

filter.

- get an Andair gascolator - if you have to have it then get one that is

well made (so you can worry less about leaks and such) 



Carl



--

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kearney

Joined: 20 Sep 2008
Posts: 563

Posted: Wed Jun 10, 2015 3:00 pm Post subject: Re: Gascolator locations

Hi Dan



I have felt your pain.....



This is what I installed prior to getting TC permission to ditch my gascolators.



http://www.aircraftspruce.com/catalog/appages/usher.php



I used these as they were a) cheap, b) simple and c) easy to install. I still have my mounting brackets - they are your if you want them.



<rant>

 IMNHO opinion, gascolators serve no purpose in a low wing a/c unless the laws of physics are repealed and water can flow up hill Gascolators, in our application function as little more than gas bombs when placed in high heat areas or as a source of vapour lock when placed on the suction side of the fuel pumps



<rant>



Anyway,  what I did to get past the MDRA inspection was to install the gascolators in the wing roots. Using the user gascolators I installed plugs, not quick drains as I did not want risk the suction lifting the drain and introducing air into the fuel system. I mounted the plugs so I had access to them under neath the wing through the bottom wing root faring. I never planned to remove the plugs as any water would be removed using the tank sumps, which were the lowest point in the fuel sumps. But I did have access to them which met the requirement of the CARS exemption that MDRA requires you meet.



I would not place the gascolator on the firewall as it only serves to introduce a volume of fuel in an aluminum container that would easily melt if there was an engine fire.



For similar reasons, I would not use the tunnel. If I could I would have kept all fuel lines out of the cockpit but in the -10 that is not possible. Fire in the cockpit is the only thing about flying that scares me.



As the Usher gascolators  have screens, you could use them as  as additional fuel filters located in the wing roots. I would not use quick drains on them for the reason noted above.



Cheers



Les



Postscript for those south of the 49th parallel....



In Canada, amateur built aircraft are inspected by MD-RA, an agency delegated inspection authority by Transport Canada (our FAA equivalent). There inspection process is based on Appendix A of CARS 549.01. This appendix exempts amateur built aircraft from the requirements of 549.01 but does require installation of a gascolator. It would be interesting to see what MD-RA would do if confronted with an electric aircraft - how would you install a gascolator and where? 

When I swapped my Subaru engine for an IO-540, I was reinspected and my CofA reissued. In this case the inspection was done by Transport Canada and not MD-RA. For this inspection, I conformed my a/c to the requirements of CARS 549.01 and not the exemption. As a result, I was not required to have gascolators as they are only required by the exemption.  Unfortunately this option is not available to builders getting their initial inspection done as all initial inspections are done by MD-RA and they only use the exemption.

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glastar(at)gmx.net
Guest

Posted: Thu Jun 11, 2015 1:26 am Post subject: Gascolator locations

2nd try

     

     

     On 11.06.2015 09:14, Werner Schneider       wrote:

     

      	  Quote: 	
		                Hi Dan,

       

       in the UK there is a 10 flying with a gascolator in the setup       before the fuel pump

       

       [img]cid:part1.08070806.02010807(at)gmx.net[/img]

       

       He has several 100 hrs without any issue, I plan to do the same       just will have the Andair pump instead.

       

       Makes inspection a bit easier as well.

       

       Cheers Werner

       

       On 10.06.2015 22:47, Dan Charrois         wrote:

       

        	  Quote: 	
		            	  Quote: 	
		  --> RV10-List message posted by: Dan Charrois <dan(at)syz.com> (dan(at)syz.com)



Hi everyone.



I'm in Canada, and stuck with an obsolete regulation that we require gascolators in homebuilt planes.  ....



I see three locations where they can be installed - in the wing roots, in the tunnel, or on the firewall.

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trigo(at)mail.telepac.pt
Guest

Posted: Thu Jun 11, 2015 12:28 pm Post subject: Gascolator locations

Dan



Can you "install" the gascolator outside the fuel circuit, just for regulation purposes?...



It seems but it is not a joke!



Carlos



Enviado do meu iPhone



No dia 10/06/2015, às 21:47, Dan Charrois <dan(at)syz.com> escreveu:



 	  Quote: 	
		   

 

 Hi everyone.

 

 I'm in Canada, and stuck with an obsolete regulation that we require gascolators in homebuilt planes.  Though they're pretty much pointless in a low-wing fuel injected plane like the RV-10, I have no choice but to put one in.  I've done as much research as I can in trying to decide exactly where would be the "best" place to do so, but wanted to post my observations and thoughts here in case anyone can find something I've overlooked, or can assuage any of the potential pitfalls I see in different scenarios due to your own experience.  No matter where I install it, the specific gascolator I am considering is the Andair GAS375 - as it seems to be one of the better constructed.

 

 I see three locations where they can be installed - in the wing roots, in the tunnel, or on the firewall.

 

 Firewall:  Advantage - relatively straightforward to install there.  Disadvantages - If an O-ring or something starts to leak, it would spray fuel around the engine compartment under pressure (are potential leaks of this sort a real possibility to consider?).  That can't be a good thing.  Also, under the hot cowling, would it cause an increased potential for vapour lock?  It may also not be the true "lowest" point in the fuel system, which the regulations also specify.

 

 Tunnel:  Two options here - adding it as another device in the tunnel, or replacing the fuel filter already there with the gascolator.  On first glance, replacing the fuel filter seems to be the way to go since the addition of the gascolator wouldn't be adding a new point of failure - just replacing one.  Though when I checked with Van's about this, they recommended against it - they would rather see the recommended filter still in place, and the gascolator added elsewhere.  In any case, whether adding the gascolator on its own, or replacing the existing filter, an advantage would be that it should be less likely to contribute to vapour lock, provided that tunnel heat isn't excessive.  Disadvantages - there is still the possibility of spraying fuel under pressure if it were to fail, and in the tunnel seems just as bad (if not worse) than the engine compartment.  Secondly, the fuel drain for the gascolator would be in the vicinity of the exhaust pipes.  I've had first-hand ex!

 perience with fuel tank drains leaking and dribbling due to debris that ended up getting into the seal.  If it were to dribble fuel into the hot exhaust gases, again that can't be a good thing.

 

 Wing roots:  Advantage - they'd be cool out there so wouldn't contribute to vapour lock.  Also, if they started leaking (either through O-rings failing or the drain dribbling), it's less of an issue.  Plus, since there would have to be two, if one did start to leak in a spectacular fashion, there is the redundancy of two, so at least the fuel in one of the wings would stick around.  And they wouldn't be pressurized there, so leaks should be less dramatic.  Disadvantages - Cost would be twice as much, since two would be needed.  There would be no way to shut off the fuel prior to the gascolators for cleaning the filter, so the tanks would have to be drained to do so (I wouldn't want to introduce yet another point of failure by installing shutoff valves before them)  Also, the gascolator would have fuel sucked through it rather than pushed through it, so it would be under a small amount of negative pressure rather than positive pressure (more so when the filter starts to get d!

 irty) - would this cause potential problems with air possibly be introduced through the drain port?  Or is the seal and spring on the drain port more than strong enough to maintain a seal against the outside even when being sucked up with the negative pressure?

 

 I hate having to install a gascolator in the first place, and it doesn't help to have not come up with a clear winner with regards to location.  Any advice anybody could give would be greatly appreciated.  Am I overlooking anything, or equally, overstating the likelihood of certain failure scenarios?

 

 Thanks!

 

 Dan

 ---

 Dan Charrois

 President, Syzygy Research & Technology

 Phone: 780-961-2213

- The Matronics RV10-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

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