From: RWolf99@aol.com
Message-ID: <75.1bba462e.28e4b8f0@aol.com>
Date: Thu, 27 Sep 2001 13:16:32 EDT
Subject: Re:  6' Fuel Probes
To: lancair.list@olsusa.com
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In a message dated 9/26/01 10:46:04 PM, Jim McKibbin wrote:

<<On September 23, 2001 Rob Wolf suggested drilling a hole in the standpipe to
vent it.....I must respectfully disagree with this suggestion. This is 
tantamount to
venting the fuel system inside the cockpit! >>

Jim -

Thanks for your very detailed response on this issue.  While reading it, it 
became clear that y'all are talking about a standpipe EXTERNAL to the fuel 
tank.  I had thought that you were talking about a standpipe INSIDE the fuel 
tank.  With the standpipe inside the tank, there's no problem with fuel 
vapors from the standpipe vent hole.  Obviously, we can't vent the fuel tank 
to the inside of the plane.  Sorry for the misunderstanding and I hope nobody 
follows that suggestion.

But you're absolutely right about one thing -- the top of the standpipe needs 
to be vented to the same pressure as the ullage (gas space) in the fuel tank. 
 This can only be done by venting the top of the standpipe back into the fuel 
tank or it's own corresponding vent line, since all the other approaches 
introduce unacceptable errors.

The obvious solution (to me, anyway) is to vent the top of the external 
standpipe back into the fuel tank.  Hard to imagine how this could be done 
without setting up a siphon.  Maybe a bulkhead fitting on the inboard rib of 
the fuel bay, with a long aluminum tube along the top surface of the wing out 
to the filler cap area.

I suppose you could have one master fuel vent, plumbed to each tank and to 
the standpipes, but that seems like a lot of complexity to me.  Isn't the 
standard system good enough?  A capacitance probe angled upwards from the 
inboard lower portion of the tank?

- Rob Wolf
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