X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from wproxy.gmail.com ([64.233.184.195] verified) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 986832 for flyrotary@lancaironline.net; Wed, 15 Feb 2006 20:16:07 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.233.184.195; envelope-from=russell.duffy@gmail.com Received: by wproxy.gmail.com with SMTP id i28so61740wra for ; Wed, 15 Feb 2006 17:15:23 -0800 (PST) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:from:to:subject:date:message-id:mime-version:content-type:x-priority:x-msmail-priority:x-mailer:importance:in-reply-to:x-mimeole; b=IFCcIUG7LuyjSibLdOOrmyo65RRfYusKoq/ZdlQERGeL45hS8Uw9SZX4vcQEbW/7mQWe9/7gQtpe16/CxB/fRVeSawodeEtsAgheY+Aj0iLmVfSqTF1nxb+dfkxZ7/QcRzJqJWnGyelO/Mq8xsANKfAwLx7L1kdk8OH84aeSNPo= Received: by 10.54.77.15 with SMTP id z15mr309449wra; Wed, 15 Feb 2006 17:15:22 -0800 (PST) Return-Path: Received: from rd ( [65.6.194.9]) by mx.gmail.com with ESMTP id 26sm276325wrl.2006.02.15.17.15.22; Wed, 15 Feb 2006 17:15:22 -0800 (PST) From: "Russell Duffy" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Fuel return line Date: Wed, 15 Feb 2006 19:15:22 -0600 Message-ID: <000401c63296$76046300$6101a8c0@rd> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0005_01C63264.2B69F300" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670 This is a multi-part message in MIME format. ------=_NextPart_000_0005_01C63264.2B69F300 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable 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. =20 =20 Will this work? Or am I missing some obvious cavitation/starvation = problem? =20 =20 Hi Chris, =20 Returning fuel as you suggest is mighty tempting, but fight the = temptation :-) =20 =20 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. =20 =20 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 :-) =20 Rusty (RV-8 QB arriving Tuesday) =20 =20 =20 ------=_NextPart_000_0005_01C63264.2B69F300 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
My plan is to copy = Tracy's fuel system=20 with one tank feeding the other, and the second tank feeding the engine = with a=20 return line.  But today I looked at one of the drawings Vans = sent me=20 (DWG 31A for the RV-8).  It is for the RV-8A, so I had ignored it=20 before.  It shows the return line from the engine (or pump) = connecting back=20 to the feed line just after the tank selector valve.  This seems to = me like=20 an easier answer. I wouldn't have to add a second pump to move fuel = between=20 tanks, and the return line would only have to go to the valve, instead = of all=20 the way to the wing. 
 
Will this work?  Or am I = missing some=20 obvious cavitation/starvation problem? 
 
 
Hi Chris,
 
Returning fuel as you suggest is mighty = tempting, but fight=20 the=20 temptation  :-)    
 
A few people have been successful with using a = small header=20 tank in that general location in the fuel system, and then return fuel = to=20 that.  I think most everyone on the list would agree that you're = MUCH safer=20 if you return to the tank itself.  = Not only is the fuel heated some, but there's evidence that air = bubbles=20 will form in the line downstream from the regulator.  Also, if a = little bit=20 of water got in the line, it's better to send it back to the tank, where = it will=20 take a few minutes to get back to the=20 pickup.  
 
Tracy's system is simple, and probably as = good as any,=20 but it's not without it's drawbacks.  The more you think about it, = the more=20 you'll realize there's at least 100 different ways to make the fuel = system, and=20 none are perfect.  You can really drive yourself nuts thinking = about=20 it :-)
 
Rusty (RV-8 QB arriving=20 Tuesday)   
 
  
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