wings_level Posted February 2, 2020 Report Share Posted February 2, 2020 So I’ll start by saying that we all know flying into known icing is a no no. But sometimes you may inadvertently get into an icy situation especially this time of year. I was flying along and started picking up rime ice. Pilot tube froze, so pitot heat fixes that problem. Leading edge was icing pretty good too. However as I was descending to get out of the ice, I started smelling fuel. So I look around and wow, fuel streaming out the trailing edge of right wing. Now, the right wing was full of fuel, but not overfull. Fuel was not coming from the cap, coming from underneath. I was feeding from the left wing, not the right. When I landed, sure enough blue stains under the flap and some had made its way on top of the flap. The plane has fuel bladders. Bladders about 9 years old. This has never happened before. Lost maybe 3-5 gallons from the leaking right tank. Filled the left tank and headed home. Stayed at low altitudes to keep everything warm. No ice heading home and no more fuel leakage. Wonder what caused the leakage? Could fuel vent have iced over creating a vacuum in that tank, but then how did it leak out? And I wasn’t pulling any fuel from that tank. Didn’t notice any signs of the bladder collapsed. Why did it not leak heading back? Things I am pondering. Open to any ideas you smart folks may have. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted February 2, 2020 Report Share Posted February 2, 2020 At altitude the tank pressure would be higher than ambient, so the fuel will be under pressure if the vent is not working. I would fill and let it sit on the ground, look for dripping. Tom Quote Link to comment Share on other sites More sharing options...
wings_level Posted February 2, 2020 Author Report Share Posted February 2, 2020 6 minutes ago, ArtVandelay said: At altitude the tank pressure would be higher than ambient, so the fuel will be under pressure if the vent is not working. I would fill and let it sit on the ground, look for dripping. Tom Thanks Tom. I didn’t fill it back up, but I have checked for drippings on the floor after letting it sit for a while. Nothing. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted February 2, 2020 Report Share Posted February 2, 2020 22 hours ago, wings_level said: Thanks Tom. I didn’t fill it back up, but I have checked for drippings on the floor after letting it sit for a while. Nothing. That may just mean the leak is at the top of the tank. 1 Quote Link to comment Share on other sites More sharing options...
kortopates Posted February 3, 2020 Report Share Posted February 3, 2020 That's a pretty serious leak if you can see it streaming out. I've only seen that much coming out of a cocked cap but realize yours is coming from elsewhere. You should be able to at least eliminate the vent as a possible source by following the blue stain and if not the cap or vent you likely have a real leak somewhere. And apparently a big one but hopefully just from the top of tank as Tom suggest since it stopped on it's own with still a lot of fuel in the tank.Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
0TreeLemur Posted February 3, 2020 Report Share Posted February 3, 2020 (edited) On 2/1/2020 at 6:27 PM, wings_level said: So I’ll start by saying that we all know flying into known icing is a no no. But sometimes you may inadvertently get into an icy situation especially this time of year. I was flying along and started picking up rime ice. Pilot tube froze, so pitot heat fixes that problem. Leading edge was icing pretty good too. However as I was descending to get out of the ice, I started smelling fuel. So I look around and wow, fuel streaming out the trailing edge of right wing. Now, the right wing was full of fuel, but not overfull. Fuel was not coming from the cap, coming from underneath. I was feeding from the left wing, not the right. When I landed, sure enough blue stains under the flap and some had made its way on top of the flap. The plane has fuel bladders. Bladders about 9 years old. This has never happened before. Lost maybe 3-5 gallons from the leaking right tank. Filled the left tank and headed home. Stayed at low altitudes to keep everything warm. No ice heading home and no more fuel leakage. Wonder what caused the leakage? Could fuel vent have iced over creating a vacuum in that tank, but then how did it leak out? And I wasn’t pulling any fuel from that tank. Didn’t notice any signs of the bladder collapsed. Why did it not leak heading back? Things I am pondering. Open to any ideas you smart folks may have. Wow. Weird. I had an acquaintance with a Bo that would leak fuel out of the cap when it was full, until it got down far enough to break some kind of siphon. The fuel smell created by that action was really strong in the cabin, and you could see the fuel streaming out from under the cap. What you are describing is much weirder than that. I'm a fluids guy, and I cannot think of what would cause that. A minuscule chance that somehow the ice changed the flow of air around the wing enough to pressurize the some volume inside of your wing, which would squeeze the fuel bladder from the outside. That sounds crazy to me, because I know that the wing is open to the cabin, do the inside of the wing and the inside of the cabin should be at the same pressure. A blocked vent would not pressurize a fuel cell. With no fuel being pulled from it, there would be no vacuum created either. Hmmmm. Edited February 3, 2020 by 0TreeLemur clarity, detail. Quote Link to comment Share on other sites More sharing options...
Shiny moose Posted February 3, 2020 Report Share Posted February 3, 2020 If i overfill my tanks i will loose fuel out of the fuel caps (I have locking fuel caps) and it comes out of the lock tumbler. A bit strange to see until i realized what was happening. Check your orings on your caps, theres a guy on here selling kits Quote Link to comment Share on other sites More sharing options...
skydvrboy Posted February 3, 2020 Report Share Posted February 3, 2020 @wings_level Perhaps it's a silly question, but were you flying coordinated? I had fuel pouring out of a wing once when it was completely full and I was doing a hard slip to give my son a better look at a military base we were flying over. I wouldn't think that would happen unless you were intentionally in a hard slip though, not in a normal flight profile. Quote Link to comment Share on other sites More sharing options...
EricJ Posted February 3, 2020 Report Share Posted February 3, 2020 4 hours ago, 0TreeLemur said: A blocked vent would not pressurize a fuel cell. With no fuel being pulled from it, there would be no vacuum created either. Hmmmm. A blocked vent also prevents a tank from depressurizing when moving to lower pressure or higher temperature. It doesn't take much to start pushing fluid out elsewhere. Quote Link to comment Share on other sites More sharing options...
0TreeLemur Posted February 4, 2020 Report Share Posted February 4, 2020 1 hour ago, EricJ said: A blocked vent also prevents a tank from depressurizing when moving to lower pressure or higher temperature. It doesn't take much to start pushing fluid out elsewhere. Going up, fuel cools and shrinks- potentially decreasing pressure inside the bladder, but not much if at all. Climbing causes air in the tank to expand, and increases pressure inside the bladder, which is a greater effect. The result would be increased pressure in the gas phase inside the bladder. But... a hypothetical rime ice plug on a vent tube would easily pop off in response to this pressure inside the bladder. That's why it seems to me that a more likely explanation is that somehow air on the outside of the bladder expanded, squeezing it, and causing fuel to leak out of the bladder. Just a WAG with 0.0 data units to support it. Quote Link to comment Share on other sites More sharing options...
carusoam Posted February 4, 2020 Report Share Posted February 4, 2020 Be on the search for connectors between the fuel cells... they are rubber hoses held together with hose clamps... Find out who the manufacturer of the system is, find a drawing of the parts list.... Chase down what isn’t connected properly any longer... There are pics of bladder installs around here... that’s where I learned about Mooney bladders... Flight into known icing is OK... when equipped with a Mooney/TKS FIKI system... Blocked fuel vents can cause some serious problems... the wings start to get oil canned as the fuel gets drawn out... relieving the vacuum...? Possibly opening the fuel drain? Noticing the problem during pre-flight... if the tank shows signs of pressure or vacuum when checking the fuel level... this is an obvious no-go... obvious now... There are several Mooneys that have gotten updated tank vent protectors... a mast that blocks ice from jamming into the vent tube... see if your bladder STC came with the vent protector mast device... FIKI systems have heated vents, I believe... Modern Mooneys have a recessed vent, less like to accumulate ice this way... PP thoughts only, not a mechanic... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
rbridges Posted February 4, 2020 Report Share Posted February 4, 2020 11 hours ago, carusoam said: There are several Mooneys that have gotten updated tank vent protectors... a mast that blocks ice from jamming into the vent tube... see if your bladder STC came with the vent protector mast device... I was wondering what that was for. I figured it had something to do with pitot air flow. 1 Quote Link to comment Share on other sites More sharing options...
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