REFLECTOR: Vent Check Valve No-Yes

[Glenn Babcock]

The check valve goes on the alternate vent inside the cabin.  You put a T-fitting In the vent line and run one side out of the cabin, the other side in the cabin with the check valve.  It's a backup in case the exterior vent is clogged. I have this setup, works great. 

Regards,

Glenn


On Mar 13, 2011, at 3:59 PM, Scott Derrick <scott at tnstaafl.net> wrote:

> 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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> 
> -- 
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