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tank vent and drain taps

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kheindl(at)msn.com
Guest

Posted: Sun Jun 23, 2013 4:36 am Post subject: tank vent and drain taps

Having recently re-arranged/replaced all fuel lines, vent lines and sight tube I am still at odds with two items:



1. What exactly is the reason again for having the tank vent in the airstream instead of a static position? Are we doing this because everybody else has always been doing it or is there a real safety aspect ? I have been given six reasons, but none of them make sense to me and there is no proof. A static vent can handle any air flow in and out of the tank. I don't see the need for pressurization, especially since this must be miniscule, in a pump driven system. Maybe in a gravity fed fuel system it might make sense, or where there are two fuel tanks. Some of you have moved the vent to the bottom of the fuselage, where it could easily be clogged by mud or insects. It has happened twice to my pitot tube.

2. Why has no PFA/LAA or other inspector ever pointed out the fact that the drain tap arrangement is completely useless ? There would have to be an awful lot of water in the tank before any of it would show up in a drain cup.

But it could get to the engine in a steep descent. The obvious reason is the high point of the fuel exits and the high barb fitting on the taps themselves. This would be especially so in a mono. The only sensible installation would be flush fitting taps in the tank itself. I am tempted to remove that plumbing  and use the tap on my mini-gascolator .

Karl

 		 	   		  

  [quote][b]

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frans(at)privatepilots.nl
Guest

Posted: Sun Jun 23, 2013 5:48 am Post subject: tank vent and drain taps

On 06/23/2013 02:36 PM, Karl Heindl wrote:



 	  Quote: 	
		   1. What exactly is the reason again for having the tank vent in the

 airstream instead of a static position? Are we doing this because

 everybody else has always been doing it or is there a real safety aspect

 ?


	


I think it is the first. Especially when you have the tank vent

connected to the cobra, there is no risk of sucking the fuel out of the

tank even if there would be a negative pressure.



 	  Quote: 	
		   I don't see the need for pressurization, especially since this

 must be miniscule, in a pump driven system.


	


In our soft tanks pressurization is even harmfull. It may cause the tank

to jam the aileron control, or abrasion of the tank when it repeatedly

expands, or other bad things. Best thing would be a neutral or slightly

negative pressure (the latter helping to keep fuel fumes out of the

cockpit). Like you said, we don't have gravity fuel feed like Cessna's

but we are dependant on a fuel pump anyway.



 	  Quote: 	
		   2. Why has no PFA/LAA or other inspector ever pointed out the fact that

 the drain tap arrangement is completely useless ? There would have to be

 an awful lot of water in the tank before any of it would show up in a

 drain cup.


	


I never got any drop of water out of these drains, and have never heard

of anyone else who got any water out of it.

(If anyone has, I would like to hear about it, and also whether this

water showed up in the gascolator as well).



Instead, I think the drains and associated plumbing are increasing the

risk of leaks, and are a hazard during an accident: if the gear is

ripped off the next thing to contact the ground and be ripped off are

the fuel drains, and together with the unavoidable sparks this will for

sure trigger a fire. And the drains can not be closed with the fuel

valve so there is nothing you can do about it.



The next time I will have maintenance on the fuel plumbing I will take

the drains out. It is just a matter of judging the safety advantages

against the safety disadvantages, and to my judgement the latter puts

more weight in the equation here.



The only things I found them useful for is for draining the entire tank

for maintenance and inspection (I have valves that can be locked in the

open position) and to fill the bottle of my camp stove. But all this can

also be accomplished by other methods.



Avoiding water in the tank can also be accomplished by refueling after

each flight so there is only little air left in the tank. Having said

that, I was surprised after the winter stop in an unheated barn with

only a little fuel in the tanks that despite all the temperature cycles

(and associated "breathing" of the tank) and our wet climate that no

water at all condensed in the tank, not a single drop!



Also, how is this arranged with cars? I have never seen a car with a

fuel drain, but yet water in the fuel seems to be unheard off (obvious

causes of forgetting to put the cap on the tank not counting). What's

the story here?



 	  Quote: 	
		   The obvious reason is

 the high point of the fuel exits and the high barb fitting on the taps

 themselves.


	


I have copper tubes inside the tank running to a position lower than the

fuel outlet for the engine. So in theory it could work.



Frans

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ptag.dev(at)tiscali.co.uk
Guest

Posted: Sun Jun 23, 2013 3:00 pm Post subject: tank vent and drain taps

Hi! Franz/all.

I can confirm that Once in particular when parked overnight at ZelamZee in a

particularly violent down pour I emptied about half a litre of water from

one of my water drain taps .

Since then I have tried to ensure that the whole tank filler cap is blanked

off by tape especially the lock.

I do have a mop out access hole in the tank top and most winter grounding

periods I drain out and mop out to ensure both tanks are started with a

clean charge of fuel. I have also occasionally had small amounts of water

show depending on the level parking of the aircraft too.

Regards

Bob Harrison G-PTAG



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frans(at)privatepilots.nl
Guest

Posted: Mon Jun 24, 2013 1:48 am Post subject: tank vent and drain taps

On 06/24/2013 12:59 AM, Bob Harrison wrote:

 	  Quote: 	
		   

 

 Hi! Franz/all.

 I can confirm that Once in particular when parked overnight at ZelamZee in a

 particularly violent down pour I emptied about half a litre of water from

 one of my water drain taps .

 Since then I have tried to ensure that the whole tank filler cap is blanked

 off by tape especially the lock.

 I do have a mop out access hole in the tank top and most winter grounding

 periods I drain out and mop out to ensure both tanks are started with a

 clean charge of fuel. I have also occasionally had small amounts of water

 show depending on the level parking of the aircraft too.


	


Ok but in your case it seems that the water is due to rain water

invasion via the fuel cap.

I'm more concerned about water condensation in the tank, but as fas as

my experience goes in our rather wet climate, this doesn't seem to be a

problem in the Europa.



Frans

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ptag.dev(at)tiscali.co.uk
Guest

Posted: Mon Jun 24, 2013 5:54 am Post subject: tank vent and drain taps

Yes Frans, that is as near correct as can be. I'm confident that my two mini

gascolators would cater for condensation ...no problem.

Regards

Bob Harrison.



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