Mailing List flyrotary@lancaironline.net Message #29233
From: Russell Duffy <russell.duffy@gmail.com>
Subject: RE: [FlyRotary] return lines
Date: Thu, 12 Jan 2006 16:37:55 -0600
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>
Message
OK! So what size? Already have 1/4" vent, 1/2" supply. Should the return be larger then supply, similar to oil return lines? Don't want to have to do it three times (like I usually do)
 
Hi Tom,
 
Yes, you need to run return lines, unless you have some sort of header tank that can be used for the return.  I believe we can probably all agree that it's best to go back to the tank though.  If you use a system like Tracy has, where you feed from only one tank, then you can return to only that tank as well.  If you think you might ever install a duplex valve to feed/return from both tanks, then you'd better install a return on both tanks now.  (You're welcome Rich <g>).
 
You can run the returns just through the root rib, but it's somewhat better to run them to the far outboard end, similar to the way Van has you run the vent line.  It gets the warmer fuel outboard, away from the pickup, and positions it in an air pocket, so there won't be any backpressure on the return line.  You can also run the pumps for a few minutes to aid in mixing the oil into the fuel if you're using premix.   
 
As for the size, there's no need for larger return lines than what you ran for the supply, though it certainly wouldn't hurt.  I'd run AN-6 size for all the fuel lines.   
 
Cheers,
Rusty (video's were cool Bob)
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