I have a very similar problem on my Legacy. If the tanks are full, fuel leaks out of the left vent, with the airplane sitting on level ground. I bought a replacement Andair check valve, but before installing it, I tested and it flowed a decent trickle of fuel in the "checked" direction (regardless of how the valve was oriented); so I conclude that they don't completely seal. And I don't think you'd want them to, because the pressure would have to get out some way when the fuel heats up...
Further conclude that the purpose of the check valves is to prevent major outflow during yaw maneuvering.
Now, if someone can tell me why the fuel always seems to flow from my right tank to my left, with the plane parked on level ground, even with the fuel selector OFF, I'd be very interested!
On Jan 31, 2012, at 6:22 PM, Bill Bradburry wrote:
Re: [LML] Legacy fuel vent check valves.
Jim, N249B is in the paint shop as well! I was just thinking that if the check
valve doesn’t stop the flow of fuel in the wrong direction, what useful
purpose does it serve? I don’t see the need for it otherwise??? Bill B
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Jim Frank
Sent: Tuesday, January 31, 2012
6:47 PM
To: lml@lancaironline.net
Subject: [LML] Re: Legacy fuel
vent check valves.
Bill,
When I take off and my fuel tanks are full, I get fuel venting out of the wing
tips when the airplane yaws in turbulence. Right tank more than left
tank. Stops when I burn off about 5 gallons or so. I ask another
Legacy builder about this and he had the same issue. I figured it
was normal.
Jim
N23XF
(in the paint shop)
On 1/31/12 3:30 PM, "Bill Bradburry" <bbradburry@bellsouth.net> wrote: I am
concerned that the fuel vent check valves may be installed backwards or are
leaking. The fuel tanks seem to vent ok and I have not seen any problems
along those lines, but fuel runs out of the vents in the wing tips any time I
get much over a half to three quarters of a tank.
Anyone else having this problem or have advice?
Bill B
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