Return-Path: Received: from [65.33.163.242] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 4.3c1) with HTTP id 741236 for flyrotary@lancaironline.net; Wed, 16 Feb 2005 07:55:55 -0500 From: "Marvin Kaye" Subject: Re: [FlyRotary] Re: Vapor Lock To: "Rotary motors in aircraft" X-Mailer: CommuniGate Pro WebUser Interface v.4.3c1 Date: Wed, 16 Feb 2005 07:55:55 -0500 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Transfer-Encoding: 8bit Jim Sower wrote: """ I have a canard, but I will have a Facet pump near (and below) the wing tanks to PUSH the fuel through the filter and fuel flow transducer. I don't want the HP pumps to SUCK through the filters and etc. for fear of vaporizing the fuel. """ This doesn't make any sense to me, but perhaps I'm missing something. The HP pumps are capable of moving LOTS more fuel than a Facet pump. Consequently, it seems to me that the HP pumps would actually be drawing fuel through the Facet pump when they're switched on, simply because the Facet can't keep up with what's being drawn out of the sump tank by them. Additionally, a return system needs 2 flow transducers, one for the feed line and one for the return... then the display instrument's electronics deduct the return flow from the feed flow to properly calculate actual through-the-injectors instantaneous flow data. (The EI fuel flow instrument uses an FFDM-1 (fuel flow differential module) to do the job, GRT EIS does it itself, as do other flow instruments with both feed and return inputs.) As long as the filters are rated to flow as much fuel as the HP pumps are capable of pushing I don't see that (vapoization) as an issue. The filter elements do need to be kept clean, and are a replace-at-annual item.