Mailing List flyrotary@lancaironline.net Message #30262
From: Russell Duffy <russell.duffy@gmail.com>
Subject: RE: [FlyRotary] Fuel return line
Date: Wed, 15 Feb 2006 19:15:22 -0600
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>
Message
My plan is to copy Tracy's fuel system with one tank feeding the other, and the second tank feeding the engine with a return line.  But today I looked at one of the drawings Vans sent me (DWG 31A for the RV-8).  It is for the RV-8A, so I had ignored it before.  It shows the return line from the engine (or pump) connecting back to the feed line just after the tank selector valve.  This seems to me like an easier answer. I wouldn't have to add a second pump to move fuel between tanks, and the return line would only have to go to the valve, instead of all the way to the wing. 
 
Will this work?  Or am I missing some obvious cavitation/starvation problem? 
 
 
Hi Chris,
 
Returning fuel as you suggest is mighty tempting, but fight the temptation  :-)    
 
A few people have been successful with using a small header tank in that general location in the fuel system, and then return fuel to that.  I think most everyone on the list would agree that you're MUCH safer if you return to the tank itself.  Not only is the fuel heated some, but there's evidence that air bubbles will form in the line downstream from the regulator.  Also, if a little bit of water got in the line, it's better to send it back to the tank, where it will take a few minutes to get back to the pickup.  
 
Tracy's system is simple, and probably as good as any, but it's not without it's drawbacks.  The more you think about it, the more you'll realize there's at least 100 different ways to make the fuel system, and none are perfect.  You can really drive yourself nuts thinking about it :-)
 
Rusty (RV-8 QB arriving Tuesday)   
 
  
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