Return-Path: Sender: (Marvin Kaye) To: lml Date: Sun, 04 Aug 2002 17:48:41 -0400 Message-ID: X-Original-Return-Path: Received: from imo-m02.mx.aol.com ([64.12.136.5] verified) by logan.com (CommuniGate Pro SMTP 4.0b6) with ESMTP id 1681902 for lml@lancaironline.net; Sun, 04 Aug 2002 17:41:56 -0400 Received: from Sky2high@aol.com by imo-m02.mx.aol.com (mail_out_v33.5.) id q.16c.119e58c4 (1320) for ; Sun, 4 Aug 2002 17:41:53 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <16c.119e58c4.2a7ef9a1@aol.com> X-Original-Date: Sun, 4 Aug 2002 17:41:53 EDT Subject: Re: [LML] Fuel feed practice/plumbing X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_16c.119e58c4.2a7ef9a1_boundary" X-Mailer: AOL 8.0 for Windows US sub 40 --part1_16c.119e58c4.2a7ef9a1_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 8/4/2002 3:37:43 PM Central Daylight Time, ian.crowe@sympatico.ca writes: > If you draw from both tanks at once what happens if for any reason one tank > loses its fuel before the other? Ian, Not quite the case you further described. Some of us use both wing pumps simultaneously to keep the header tank full, some even automatically (i.e. float switch) so the pumps turn off before pushing fuel overboard. The header is the only source for fuel to the boost pump (if injected) and the engine driven pump. Benefit - no selector to turn "off" or to "both" or to even switch from wing to wing every so often. Generally, the wing tanks are emptied evenly - thus no lateral re-trim requirement. Also, as Lancair recommended, the header is full for landing and takeoff. If there is a catastrophic electrical failure, you will have one hour to find an airport with the full header fuel. If only one wing or pump fails, you can fill from the other via manual pump switch. Most of us, upon detecting a fuel problem in flight will land and fix it rather than take the risk of "finishing" the trip short of our final destination (I hate the word final). Some of us also used check valves so that no fuel could go back into the wing from the header. Those who use the very complicated process of drawing fuel from each wing (using the engine pump) and who did not build a slosh tank in the wing are in danger of unporting the wing draw at a bad moment -- never a concern with the header unless you are working on the last 2 gallons of fuel in the airplane - yes, we also pump each wing down to the last cup of fuel. The pumps don't care if they run "dry" for a short while. Scott Krueger LNC2 - N92EX --part1_16c.119e58c4.2a7ef9a1_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 8/4/2002 3:37:43 PM Central Daylight Time, ian.crowe@sympatico.ca writes:

If you draw from both tanks at once what happens if for any reason one tank
loses its fuel before the other?


Ian,

Not quite the case you further described.  Some of us use both wing pumps simultaneously to keep the header tank full, some even automatically (i.e. float switch) so the pumps turn off before pushing fuel overboard.  The header is the only source for fuel to the boost pump (if injected) and the engine driven pump.  Benefit - no selector to turn "off" or to "both" or to even switch from wing to wing every so often.  Generally, the wing tanks are emptied evenly - thus no lateral re-trim requirement.  Also, as Lancair recommended, the header is full for landing and takeoff.  If there is a catastrophic electrical failure, you will have one hour to find an airport with the full header fuel.  If only one wing or pump fails, you can fill from the other via manual pump switch.  Most of us, upon detecting a fuel problem in flight will land and fix it rather than take the risk of "finishing" the trip short of our final destination (I hate the word final).  Some of us also used check valves so that no fuel could go back into the wing from the header. 

Those who use the very complicated process of drawing fuel from each wing (using the engine pump) and who did not build a slosh tank in the wing are in danger of unporting the wing draw at a bad moment -- never a concern with the header unless you are working on the last 2 gallons of fuel in the airplane - yes, we also pump each wing down to the last cup of fuel.  The pumps don't care if they run "dry" for a short while.

Scott Krueger
LNC2 - N92EX
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