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Fuel vent scar


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Something strange happened to me yesterday. I took off from MGGT (5000 feet MSL), it was very hot, with full tanks (I have bladders installed) after take off to my surprise I saw that I was venting fuel! After about the longest 5 minutes of my life it stopped, but I landed as soon as possible. After I landed I checked and realized that the fuel had left the tank through the fuel vent....is this something to be expected with full tanks on a hot day? Or is there something I should check...

As usual any suggestions?

Oscar

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Left to my own, I fill my non-bladder tanks up to about ½" from the cap to leave expansion room. I've seen fuel drip from the vents on various high-wing planes. Thermal expansion is why the vents are there, and they help fuel exit through the pump, too.

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Might want to check your vents on the bottom of the wing. Insects have been known to build in and clog those. Some years ago a twin that had been sitting for a while took off. The vacumn in the tanks bought the airplane down. The pilot was lost and a valuable Mooney related business essentially ended with him.

Just blow in them lightly to see that they are clear. You might need a short length of plastic tube, unless you are acrobatic.

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Fuel tank vents on Mooneys and other planes are designed to keep the tank pressurized. This helps the engine pump to suck the fuel at altitude. The vent opening should be facing into the airstream so it can pressurize the tank in-flight. If the opening is facing to the back or to the side the vent will create suction that will pull out the fuel at the very top of the tank. Check the fuel tank vent opening alignment and the vent itself rigidity.

 

José 

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Fuel tank vents on Mooneys and other planes are designed to keep the tank pressurized. This helps the engine pump to suck the fuel at altitude. The vent opening should be facing into the airstream so it can pressurize the tank in-flight. If the opening is facing to the back or to the side the vent will create suction that will pull out the fuel at the very top of the tank. Check the fuel tank vent opening alignment and the vent itself rigidity.

 

José 

Jose,

Thank you for that tip. Indeed I see that my fuel vent is facing backwards! Is that even the case if you have bladders installed? 

 

Oscar

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Jose,

Thank you for that tip. Indeed I see that my fuel vent is facing backwards! Is that even the case if you have bladders installed?

Oscar

Oscar -- do you have bladders or wet wings? Either way the vents should be facing forward. If you have bladders, whomever did the installation but them on incorrectly. In addition, if you have bladders, there should be an anti-ice mast in front of the vent.

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Jose,

Thank you for that tip. Indeed I see that my fuel vent is facing backwards! Is that even the case if you have bladders installed? 

 

Oscar

Specially on bladder tanks it should be facing forward. Facing backward will create suction and possible collapse of the bladder. Unlike integral tanks bladders are just bags that need to be inflated to maintain maximum volume.

 

José  

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Oscar,

 

  My bladder vents face forward. My vents are under the leading edge, impossible to see from inside the airplane.

 

That's what I was thinking. However, after I posted my question about this above, I came to assume that he was seeing fuel leaking out around the filler caps. That's all I can figure. I thought the caps sealed better, but I guess maybe not.

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Fuel vented through the Bladder vents, not the filler caps. I checked the fuel marks after I landed. This is how they are installed in my plane. Does this look right to you guys?

 

Thanks

 

gallery_8898_13598_59292.jpg

No that's not right. They should face forward. Plus there is an AD to have an airfoil fuel deicer mounted forward of that vent as well
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I think that Jose and Chris are right, Oscar, in that your vents are installed backwards and that you don't appear to have ice masts installed in front of them.  I would call Myron at O&N and get his email address so that you can send this picture to him.  He will tell you what you need to do.  Myron's number at O&N is 570-945-3769. 

 

Jim

 

Thanks guys, will call them on Monday.

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The AD also includes removing the bladders and installing foam wedges under them. There is also a completely crazy hole to drill in the crankcase vent tube that they somehow managed to include in the AD. This AD has been around since the late 90's, scary that something this visible could have been missed this many times.

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The AD also includes removing the bladders and installing foam wedges under them. There is also a completely crazy hole to drill in the crankcase vent tube that they somehow managed to include in the AD. This AD has been around since the late 90's, scary that something this visible could have been missed this many times

 

I just installed the additional bladders, so I had the wedges installed under them. The fuel caps are also part of the AD, as well as the rods. But for bladders installed before 98.

 

here is the link to he AD:

Mooney Bladders

Mooney Bladder Airworthiness Directive & Service Bulletin Information

Airworthiness Directive 24-25-04 was issued effective January 21, 2005, based on our Mandatory Service Bulletin ON-100 dated February 1, 1998. A copy of the Service Bulletin is posted for your reference.

The Airworthiness Directive applies to Mooney bladder systems installed prior to February 1, 1998.

The parts required for compliance include the foam pieces with drains and hardware and the anti-ice masts with hardware. All bladders sold by O&N after February 1, 1998 incorporated these changes. These parts are available from O&N Aircraft for $500($250 for each component). For those desiring to purchase the raised fuel caps, they are available for $250 for both caps.

The raised fuel caps recommended in the Service Bulletin are optional. Purchasers of our kits have consistently requested the flush Shaw Aero fuel caps. At the time the Service Bulletin was written in 1998, O&N was not aware of the requirements for the Alternate Method of Compliance. As specified in the Airworthiness Directive, owners will need to insert the “Pilot Operating Procedures–Preflight Fuel System Check” in the Pilot’s Handbook.

To order Service Bulletin parts or if you have questions, please feel free to contact O&N Aircraft Modifications.

 

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/6FF2EEBA54075BB686256F65005B79BC?OpenDocument

 

 

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Oscar, the vent looks slightly bent backward. Is that piece of rubber hose or a tube?. If it is a hose it will bend backwards in the airstream possibly causing fuel syphoning even with the opening facing forward.

 

A quick fix without removing the bladder is by cutting another fishmouth hole facing forward. You can easlly do this with a Dremel tool cutting disk. Verify is not a loose vent by trying to rotate it. I find hard to believe that someone installed this the wrong way. Is the right tank facing backwards too?  

 

José 

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Oscar, the vent looks slightly bent backward. Is that piece of rubber hose or a tube?. If it is a hose it will bend backwards in the airstream possibly causing fuel syphoning even with the opening facing forward.

A quick fix without removing the bladder is by cutting another fishmouth hole facing forward. You can easlly do this with a Dremel tool cutting disk. Verify is not a loose vent by trying to rotate it. I find hard to believe that someone installed this the wrong way. Is the right tank facing backwards too?

José

It is aluminum and Believe it or not both face backwards! I will just call O&M on Monday to ensure that indeed they have to face forward and follow your advice about cutting the tube so they look forward.

I just can't believe it that four different mechanics in the US and two abroad did not catch this...thanks guys! This just proves once again that this is a great community

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Thanks guys. This is now very clear. Somebody at some point, most likely when I installed the two additional bladders simply messed up and put the vents backwards...so I am now rather pissed at them... but to fix it it seems to me that the way to do it is to cut a fish mouth into the vent so that they "look forward" .... no comments...

 

Thanks for your time and efforts, in particular Maurader and Bob for the pics, I really appreciate it !!! 

 

Oscar

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