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Slight fuel leak - top of header tank

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The fuel lines coming into the header tank each have very slight leaks at the fittings. We tightened up the fittings, which will hopefully stop the leaks. What I'm wondering, is there any sort of O-ring or washer inside the fittings that might need to be replaced? I've looked through the manuals and don't see anything regarding these fittings. (This photo is not of my airplane, but the fittings at the top of the header look the same)

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The blue nuts are a standard aircraft "B" nut for a flared fitting. They do make a special soft aluminum gasket for these fittings, but they are not normally used. The only place I have used them before is on a aircraft air conditioning system.

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My A&P mentioned the O-rings, and I thought he meant inside those fittings. However, he was referring to O-rings between the header tank and the nuts (as you can see from these photos). Fuel is weeping from between the O-rings and nuts, but no joy on info regarding these O-rings in the manual. I wish FD had fuel shut-off valves above the header tank because, of course, my tanks are full! 🤬

O-RING

E7232E68-20E1-4EE9-AB47-A880056C35F3_1_105_c.thumb.jpeg.9d49d1e77ea673be13760b2a6496abd3.jpeg

 

BULGING O-RING (possibly from tightening the fittings - don't know)

FA4FCA13-9B3D-4613-AB82-B05295BB51B6_1_105_c.thumb.jpeg.dc26807bec3cbffbb2a6ff56d5c58377.jpeg

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I think you can shut off both tanks by removing the red selector (a nut holds it on), then using a pair of pliers, make another turn on the valve and both tanks are shut off.  I saw this done.  If Tom or Roger could confirm this simple technique I’d feel better about suggesting it to you.

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8 hours ago, AGLyme said:

I think you can shut off both tanks by removing the red selector (a nut holds it on), then using a pair of pliers, make another turn on the valve and both tanks are shut off.  I saw this done.  If Tom or Roger could confirm this simple technique I’d feel better about suggesting it to you.

That’s exactly what I did at the last Annual. Works a treat.

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1 hour ago, AGLyme said:

Takes 1 minute.  Essentially there is a hidden shutoff in the valve.

I ran by the hangar and removed the selector in order to see what you're referencing. And you guys aren't just woofin' - there it is. Now I need to determine what size/type O-rings to get. Judging from the stains on the header tank, fuel has been slowly weeping out at least two and perhaps all three spots for quite a while. I sometimes get a slight fuel odor in the cockpit, while in flight, but I've been chalking it up to "airplane smells." It must've been the leaking fuel. 

IMG_4094.thumb.jpeg.afc01c18d4e72186fab95e3361c9a0dd.jpeg

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You do not need to remove the handle from the selector, just loosen the center screw enough to rotate the handle past the raised collar.

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7 hours ago, ct9000 said:

You do not need to remove the handle from the selector, just loosen the center screw enough to rotate the handle past the raised collar.

From an outsider that has no experience with this specific issue.  This maybe true, but I would NOT recommend this option, As I could see the possible failure modes of this, Such as not remembering to tighten the handle back down. Leaving the handle off is a good poke-yoke for preventing any issues with this practice. Just an opinion.

 

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On 11/24/2020 at 5:28 AM, Skunkworks85 said:

From an outsider that has no experience with this specific issue.  This maybe true, but I would NOT recommend this option, As I could see the possible failure modes of this, Such as not remembering to tighten the handle back down. Leaving the handle off is a good poke-yoke for preventing any issues with this practice. Just an opinion.

 

I hear ya but there is not a likely chance of leaving the screw loose because when you finish work on the system you can get no fuel through till you turn it back on at which point the handle is loose so you do up the screw.

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I’ve seen it done.  It’s no biggie to take it off.  I recall that the AP had to take my cover off to get to the valve with his pliers. I can see Skunk’s point, like putting the oil cap on the pilots seat.  Or never placing any tool or rag on the engine compartment lest one forgets.

Yesterday was a major milestone for me.  I went to one of those industrial hair cutting “salons” (my barber was closed) and the nice “hairdresser” said “good news, you get a senior discount”.  Dammit... Anyway these little tricks we play on ourselves can save a life.  I read a report on one of the big flying forums that a pilot forgot the gust lock... not good.

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Human beings are human beings... we try the best we can... at the end of the day, we need checklists and best practices (i.e. learning from others' calamities)  

PS, I lost my truck keys...

 

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There is no way that a properly designed, procured & installed o-ring can fail in this manner. An o-ring always sets in a gland of some type, even if it's just a chamfer around the lip of a bore. It's never just squeezed between flat surfaces. I hope that's not what's been done here.

Mike Koerner

FA4FCA13-9B3D-4613-AB82-B05295BB51B6_1_105_c.thumb.jpeg.dc26807bec3cbffbb2a6ff56d5c58377.jpeg

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Something failed because two of the three have been weeping fuel for months or longer. I only just now discovered it at annual. The header tank was stained from fuel varnish, and the area around those O-rings was damp. Like I mentioned before, I occasionally thought I smelled fuel in the cockpit, especially after the plane had sat for a while. At no time since purchase has any tightening been done on the fittings until AFTER discovering the leak last week. And even then it was just a nudge, hardly any tightening at all. Tightening seems to have resolved one of the fittings, but not the other. 

Perhaps the key is in what you said: "Properly designed, procured & installed."  Maybe something didn't wasn't done properly.  Been through this before: I had brake a fluid leak and a fuel leak in my new Aerotrek A240 back in 2013. The brake fluid leak was due to a tiny burr in a fitting which slowly chewed into the gasket. The fuel leak was from a poorly-installed gasket on the header tank. 

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