X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 15 Jun 2007 11:32:07 -0400 Message-ID: X-Original-Return-Path: Received: from [68.98.211.24] (HELO systems3.net) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTP id 2104510 for lml@lancaironline.net; Fri, 15 Jun 2007 11:00:15 -0400 Received-SPF: none receiver=logan.com; client-ip=68.98.211.24; envelope-from=cberland@systems3.net Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C7AF5D.CB532AA4" X-MimeOLE: Produced By Microsoft Exchange V6.5 Subject: [LML] Re: Boost Pump X-Original-Date: Fri, 15 Jun 2007 07:59:39 -0700 X-Original-Message-ID: <87C33F695961494D886EB3B6C8A476512F3A41@s3server.Systems3.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Re: Boost Pump Thread-Index: Aceu5bYr7RU4bypoRmeN+x8FgGwV2QAdLaKA From: "Craig Berland" X-Original-To: "Lancair Mail List" This is a multi-part message in MIME format. ------_=_NextPart_001_01C7AF5D.CB532AA4 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Bill Wade, you did an excellent job of describing the engine driven fuel pump operation. "Bill's question is: could the output of the two pumps combine and overwhelm the return line causing pressure and thus fuel flow to go out of limits?" Yes but not just because it overwhelms the return line. The pump sends fuel to the metering valve based on more functions than the just the relief valve pressure setting. If you increase the engine driven fuel pump inlet side fuel pressure, you will increase the fuel going to the metering valve. For all folks other than the ultimate "gear heads", I feel this is what needs to be remembered. While I may be considered a gear head, I am still a little fuzzy as to the exact interactions of all the pump features. The same fuzziness emulsions tubes created when trying to figure out what the part throttle fuel curve would look like in a carburetor. =20 For those who feel this is an unacceptable risk posed by the fuel injection design, let me pose this comparison. If you are flying very close to stall and you increase the angle of attack, the plane will stall and may create a life threatening event. Did the aircraft engineer design an unacceptable aircraft? I believe there are rules that must be followed to help insure safe flight. Don't turn the freaking high boost on during short final. Don't do a mag check on short final. Don't stall the airplane on short final. The list is quite long. Personally, I never change fuel tanks while I'm in the pattern. This irritates a lot of instructors. Craig Berland ------_=_NextPart_001_01C7AF5D.CB532AA4 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
Bill Wade, you did an excellent job of = describing the=20 engine driven fuel pump operation. "Bill's = question is:=20 could the output of the two pumps combine and overwhelm the return line = causing=20 pressure and thus fuel flow to go out of limits?"  Yes but not just because it overwhelms the return = line. =20 The pump sends fuel to the metering valve based on more functions = than the=20 just the relief valve pressure setting.  If you increase the engine = driven=20 fuel pump inlet side fuel pressure, you will increase the fuel going to = the=20 metering valve.  For all folks other than the ultimate "gear = heads", I feel=20 this is what needs to be remembered.  While I may be considered a = gear=20 head, I am still a little fuzzy as to the exact interactions of all the = pump=20 features.  The same fuzziness emulsions tubes created when trying = to figure=20 out what the part throttle fuel curve would look like in a=20 carburetor.
 
For those who feel this is = an unacceptable risk=20 posed by the fuel injection design, let me pose this comparison.  = If you=20 are flying very close to stall and you increase the angle of attack, the = plane=20 will stall and may create a life threatening event.  Did the = aircraft=20 engineer design an unacceptable aircraft?  I believe there are = rules that=20 must be followed to help insure safe flight.  Don't turn the = freaking high=20 boost on during short final.  Don't do a mag check on short = final. =20 Don't stall the airplane on short final.  The list is quite = long. =20 Personally, I never change fuel tanks while I'm in the pattern. =20 This irritates a lot of instructors.
Craig = Berland

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