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From: "Paul" <sqpilot@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-726146@logan.com>
Subject: Re: [FlyRotary] Re: Vapor lock
Date: Sat, 12 Feb 2005 13:19:39 -0600
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Hi, Dale...I don't think you missed anything....It appears it was I who 
missed something....like a vent from the top of the surge tank to one of the 
main tanks.  Now it is even MORE unanimous....I need to install that vent. 
Thanks for your input and confirmation of what others are suggesting, Dale. 
Paul need a vent Conner
----- Original Message ----- 
From: "Dale Rogers" <dale.r@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, February 12, 2005 8:55 AM
Subject: [FlyRotary] Re: Vapor lock


> Paul,
>
>   There a piece missing from this puzzle.  Help me understand.
>
>> If I were returning fuel to one of the main tanks, I would think that 
>> venting the sump would be appropriate, but since I am sending fuel undere 
>> pressure back into the sump tank, I am concerned that once the sump tank 
>> is full, the additional fuel pumped back into the sump tank would take 
>> the path of least resistance....out the vent instead of back up the fuel 
>> line into the tank?
>>
>
>   When you first power-up your fuel system, you have a
> full header tank (or at whatever level remaining in the
> mains, if there's overlap).  You have an empty return line
> from the regulator to the header tank.  As soon as your
> fuel pressure exceeds the regulator setting, fuel begins
> pushing air out of the return line, into the header tank,
> creating a "head" pressure against the mains.  At some
> point, fuel pumped out of the tank equals what's coming
> back - until you start the engine.  Now less fuel is
> coming back than is being pumped out, and the difference
> should be made up from the mains.
>
>   However ... you have bubble of air and vaporized fuel
> in the header tank - only as long as the head pressure of
> the mains exceeds the pressure in the header tank, will
> fuel flow from the mains to the header tank.  Heating the
> fuel will increase the pressure of the bubble.
>
>   I suspect that the header tank should be vented back to
> the mains.
>
>   What did I miss?
>
> Dale R.
> COZY MkIV #1254
>
>
>
>>>  Homepage:  http://www.flyrotary.com/
>>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>
>
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