Mailing List flyrotary@lancaironline.net Message #22814
From: David Leonard <wdleonard@gmail.com>
Subject: Re: [FlyRotary] Re: will EFI pumps pump air
Date: Tue, 31 May 2005 09:50:51 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>

 > How does this give you redundancy? If either pump fails, you end up without access to that tank's gas.  
True, but that's not an immediate emergency, just a reason to land soon. Redundancy of fuel supply to the engine was what I was after. Anything happens to one supply - fuel contamination, leak in lines, blocked filer, failed pump etc. and you have a spare system.
John

Its not an emergency unless you have already used most (or all) of the fuel in that tank.  You may think that you never plan to run a particular tank empty.  So how much are you ALWAYS going to leave in each tank?  Probably 1/2 hour at a minimum.  That would be about 4 gal.   Which means you now have 8 gal of unusable fuel.  Or, to look at it another way,  that is 1/2 hr. of effective range you would otherwise have if you were to run the 2nd tank empty.
 
You also have to always remember to stop using that tank when there have about 4 gal left.  I find it very easy to get distracted and forget to switch exactly when I intended.  It will also be difficult to know when you have only 4 gal left, you will be conservative and usually leave more fuel than that.  This will further reduce your effective range and mean that you are carrying around 4 extra gallons of fuel (24#) EVERYWHERE you fly for the life of the plane....
 
I like to use up the fuel in my 2nd tank early while still en route, then I maximize the fuel in the tank I use while in the approach and landing phase.
 
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