Is this a fuel leak or the aftermath of a fuel spill?

aloft

aloft

New Member
Caught this today during my preflight inspection. What do you make of it? Leaky wing tank or careless line guy?

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aloft said:
Caught this today during my preflight inspection. What do you make of it? Leaky wing tank or careless line guy?
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I would be a little concerned. On our 152s the fuel guys would spill over on every fill up because they couldn't seen in very well and nothing like this showed up. On our 172s they over fill occasionally and nothing like you show.

-Rob
 
v1valarob said:
Is it dried on like that? If so.... how did no one else catch it sooner?

-Rob
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I'm the only guy that flies that airplane, and it wasn't there yesterday (during preflight, anyway...I don't generally do a post-flight walkaround, though I suppose I should). Avgas evaporates quite quickly, and when it does, it leaves the dye behind.
 
aloft said:
I'm the only guy that flies that airplane, and it wasn't there yesterday (during preflight, anyway...I don't generally do a post-flight walkaround, though I suppose I should). Avgas evaporates quite quickly, and when it does, it leaves the dye behind.
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Anytime avgas is spilled on our planes it doesn't leave any dye behind, and if it does, it isnt as dark as your pictures above. The fact that its on the bottom of the wing just means it has to be some type of leak.

-Rob
 
I had the same problem with one of our 172s two weeks ago. From what I can see, it is mainly due to overfilling the tanks.
 
or from careless people putting cracks in the filler necks by not keeping the nozzle straight while refueling it.
 
SpiraMirabilis said:
I've has experience with a 172 wing tank that the bottom had a leak in it and it looked exactly like that.
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Seen this same exact thing except the culprit was a crack in the filler neck. When I caught this, the Mechanic removed the skin from the area around the filler cap and found the weld cracked where the filler neck was attached to the tank. From what I hear it is fairly common.
 
LoadMasterC141 said:
Seen this same exact thing except the culprit was a crack in the filler neck. When I caught this, the Mechanic removed the skin from the area around the filler cap and found the weld cracked where the filler neck was attached to the tank. From what I hear it is fairly common.
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It is fairly common, it happened to a couple of our 72s, I believe the cause was the neck getting nailed with the fuel nozzle over and over again, bound to happen after a couple in years in service, though if the line crew is super extra careful ; ) it wont.
 
I have had this exact problem in the 172 I fly. The A&P that checked it out said that it was caused by the tank being left completely full and temperature changes causing the fuel feeder gasket to seep fuel where it's mated to the tank. Just don't leave it sitting out topped-off or have them fill it to about an inch below top and it should take care of it.

Clean the area off and don't top it off until you're about to fly, and I bet you won't see it anymore. Granted that it's something which should get fixed at the next service interval, but it's probably not a critical safety issue. (at least in my case it wasn't) Still have it looked at first though.
 
Cracked filler neck, worn out sender gasket, cracked feed ports, mangled fittings. Lots of things cause those tanks to leak. The 172 tanks especially like to crack on the top in the very middle due to oil canning from the constant fill/burn and hot/cold cycles.

Also, every time I take a tank out I find at LEAST one fuel dipstick in it that's been "tumbled" smooth like a rock from rolling around for years.

If you dropped the dipstick in PLEASE let someone know.
 
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