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From: William R. Bayne [mailto:[EMAIL PROTECTED]
Sent: Sunday, December 11, 2005 9:54 PM
To: Ed Burkhead
Subject: WRB Re: [COUPERS-FLYIN] Header tank question
RLYFLYIN
Hi Glen,
Ed is 100% correct. I envy his clarity and brevity.
The original "cork on a stick" has no frame of reference by which the pilot would be aware of your described difference between "full" and "slightly less than full". I presume, therefore, that you have the "Rain-Pruf" type with the exterior protective tube; and further presume that someone has marked the "full in flight" level from which the slightest drop becomes evident.
The specified fuel pump moves WAY more fuel than the engine can burn at any power setting. Even after it is throttled by the 1/16" orifice in the pump outlet fitting, there is excess fuel pumped by design as a safety "fudge factor". When the engine is operating, the "normal" fuel level maintained is determined by the "standpipe", or height of the open end of a fuel line near the top of the fuselage tank interior through which excess fuel is returned to one or both wing tanks (depending on the tanks and lines installed).
If the noted difference were significant, it could be that someone has removed the restrictor fitting from your plane or enlarged the hole in it to compensate for a worn-out pump. The fuselage tank standpipe can be bent or partially obstructed. Any of these conditions would amplify the difference in level after shutdown. Other than the (rather common) "ramp drip" loss out of the carburetor (avoidable if you shut the engine down by turning off the behind-panel fuel valve and running the carburetor dry), excess fuselage tank fuel returns to the wing tanks.
Regards,
William R. Bayne
<____|-(o)-|____>
(Copyright 2004)
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On Dec 11, 2005, at 8:32 PM, <[EMAIL PROTECTED]> wrote:
My header tank quantity indicator (cork on a stick) works fine. I shows full when the tank is full and shows appropriately less as fuel in that tank starts to burn off. If the plane sits overnight with a full header tank, the indicator will show slightly less then full the following morning. As soon as I start the engine ( and the fuel pumps starts working), the indicator goes back up to show a full tank. If some fuel leave the header tank overnight, where does it go?
Thanks.
Glen Davis CFII
Grumman Tiger N70GD
1946 Ercoupe N3103H
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