REFLECTOR: Vent Check Valve No-Yes

[Scott Derrick]

Of course not!  Do you smell fuel in a Cessna, Piper, Beechcraft, etc... 
  Their fuel vents don't have one way valves.

If you smell fuel in the cabin you have a leak!  Nothing to do with that 
one way valve.

Scott
-------- Original Message --------
Subject: Re: REFLECTOR: Vent Check Valve No-Yes
From: Mike Dawson <medawson250 at yahoo.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Date: 03/13/2011 01:42 PM

> Without the check valve in the vent line don't you get that fuel smell permeated in the interior. That is what it is for, let the air in , keep the gas out!
>
> --- On Sun, 3/13/11, Scott Derrick<scott at tnstaafl.net>  wrote:
>
>> From: Scott Derrick<scott at tnstaafl.net>
>> Subject: REFLECTOR: Vent Check Valve No-Yes
>> To: "Velocity Aircraft Owners and Builders list"<reflector at tvbf.org>
>> Date: Sunday, March 13, 2011, 11:42 AM
>> I'm not too sure about the vent check
>> valve that has been added to the kit.
>>
>> The general description of the vent system is to plumb all
>> vents, L&R tanks and sump into a block high on the cabin
>> side of the fire wall.  A feed line is plumbed into the
>> same block that travels down to the bottom of the fuselage
>> and is  positioned or set up to apply positive pressure
>> to the vent system in flight.  Mime is plumbed to a
>> little NACA scoop on the bottom of the fuselage.
>>
>> At some time after 2000,  a one way valve was added to
>> the feed line to only allow air into the system. Why?
>> I'm assuming it was to prevent fuel from leaking out of the
>> vent system in case of an accident or something?  Or
>> was there a different reason?
>>
>> I bought a valve recently and have yet to add it as I've
>> flown the plane for 600 hours with nary a problem with the
>> fuel system.
>>
>> The problem with adding this valve is it prevents pressure
>> from escaping the system.  Fuel tanks are vented to
>> allow air in and to allow vapor out when the fuel expands
>> from heat. We've all filled up an airplane, parked it on the
>> ramp, only to discover it puked a puddle of fuel onto the
>> ramp as the cool fuel heated up in the sun.
>>
>> Now that valve won't let that happen, and if your system is
>> tight you will be pressuring it as the fuel heats up. Is
>> that a problem?  I don't know..  A couple of
>> months ago I calibrated my fuel tank sensors, adding fuel
>> into each tank in 5 gallon increments until full. I had
>> planed on flying immediately after words but something came
>> up.  I pushed the plane back into the hanger but the
>> sun was shining in on the plane. I was futzing with
>> something on my workbench when I heard dripping.  I
>> looked arouns and saw a stream of fuel dripping from the
>> bottom of the fuselage!   Just like I've seen
>> from Bonanzas, Cessnas, etc..  I got all excited and
>> looked into the cabin thinking I would find a cabin full of
>> fuel, nothing.  I looked under the fuselage and could
>> then see it was coming out of the vent  It then
>> stopped.  I popped a fuel cap and left it un compressed
>> so anymore pressure wouldn't build up while the tanks were
>> completely full!  Now if I had that vent in there, the
>> pressure would have built up, and up?
>>
>> How high, I don't know.
>>
>>
>> Scott
>>
>> --
>> Stand porter at the door of thought.
>> Mary Baker Eddy
>>
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>
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