X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao07.cox.net ([68.230.241.32] verified) by logan.com (CommuniGate Pro SMTP 4.3.2) with ESMTP id 965472 for flyrotary@lancaironline.net; Fri, 27 May 2005 12:54:34 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.32; envelope-from=ALVentures@cox.net Received: from BigAl ([68.7.14.39]) by fed1rmmtao07.cox.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with ESMTP id <20050527165349.WFDE1367.fed1rmmtao07.cox.net@BigAl> for ; Fri, 27 May 2005 12:53:49 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: No fuel return for RX-8 six port Date: Fri, 27 May 2005 09:53:51 -0700 Message-ID: <000001c562dc$a8df49a0$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C562A1.FC8071A0" 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 V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C562A1.FC8071A0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable If for any reason one strake is reluctant to transfer, I can de-select = the tank that's transferring OK and suck fuel from the reluctant tank (this would be impossible if the sump were vented). =20 Both "suck" and "reluctant" are relative terms since the head pressure between the strake and the sump is quite small - 0.3 psi with full = strakes, 0.1 when empty. That's why I believe sumps should be a closed system .... Jim S. I'd say what works for you is what works. But before adding potential problems of electric valves, the requirement to use them, and the = potential for air or vapor locked in the sump tank, I would determine why I had "reluctant" gravity. There has got to be a reason, you just haven't = found it yet. You have a good 'work around' that you are willing to manage, = and that's fine; I just wouldn't generalize that to be the best approach in = all cases. =20 You also said: Your sump basically recycles completely every 4 minutes = or so. Your fuel could be really REALLY hot just when you begin your = takeoff roll. Do you have any reason to believe this; like any measurement? There is always some fresh fuel coming from the mains. How much heat is the fuel line really picking up? With a 3 gallon sump and a 30 gph pump the = recycle is clearly less than once every 6 minutes. Yeah, if I was on the = taxiway more than 20-30 minutes I might be concerned. By then I'd probably have turned off my engine a few times while I waited. I'll plan on getting = some temp measurements on my sump tank temp and we'll see. BTW, my comment about a power runup before takeoff was to bring fresh = cool fuel into the sump before takeoff. And as soon as I apply full power = for takeoff roll the fuel temp in the sump tank is going down. (Very little recycle, fuel flowing in from the mains) If there were to be an issue, wouldn't I know it at the beginning of the takeoff roll? Paul's issue = in the earlier version was not just pumps higher than the sump, but also restrictive flow into the sump. I have no objection to returning fuel to the mains; that's fine. I'm = not at all convinced that is a requirement that needs to be backfit. I'm headed of on vacation in the morning for about 10 days, so you can = say anything about me that you want:-). Al >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0001_01C562A1.FC8071A0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

If for any reason one strake is reluctant to = transfer, I can de-select the tank = that's transferring OK and suck = fuel from the reluctant tank (this would be impossible if the sump were = vented). 

Both "suck" and "reluctant" are relative terms since = the head pressure between the strake and the sump is quite small - 0.3 psi = with full strakes, 0.1 when empty.

That's why I believe sumps should be a closed system .... Jim S.

I’d say what = works for you is what works.  But before adding potential = problems of electric valves, the requirement to use them, and the potential for = air or vapor locked in the sump tank, I would determine why I had = “reluctant” gravity.  There has got to be a reason, you just haven’t = found it yet.  You have a good ‘work around’ that you are = willing to manage, and that’s fine; I just wouldn’t generalize that to = be the best approach in all cases.

 

You also said:  Your sump = basically recycles completely every 4 minutes or so.  Your fuel could be = really REALLY hot just when you begin your takeoff roll.

Do you have any reason to believe this; like any measurement?  There = is always some fresh fuel coming from the mains.  How much heat is the fuel = line really picking up? With a 3 gallon sump and a 30 gph pump the recycle is = clearly less than once every 6 minutes.  Yeah, if I was on the taxiway more = than 20-30 minutes I might be concerned. By then I’d probably have = turned off my engine a few times while I waited. I’ll plan on getting some = temp measurements on my sump tank temp and we’ll see.

BTW, my comment about a power runup before takeoff was to bring fresh cool = fuel into the sump before takeoff.  And as soon as I apply full power for = takeoff roll the fuel temp in the sump tank is going down. (Very little recycle, = fuel flowing in from the mains) If there were to be an issue, wouldn’t = I know it at the beginning of the takeoff roll?  Paul’s issue in the earlier version was not just pumps higher than the sump, but also = restrictive flow into the sump.

I have no objection to returning fuel to the mains; that’s = fine.  I’m not at all convinced that is a requirement that needs to be = backfit.

I’m headed of on vacation in the morning for about 10 days, so you can say = anything about me that you wantJ.

Al

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