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Date: Sat, 12 Apr 2008 10:41:24 -0400
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From: Thomas O'Grady <ogrady@gci.net>
Subject: Re: [LML] Re: IVP fresh air valve
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I cannot speak for all installations, but my fan does very little on  
the ground.  On the other hand, I get a lot of air once I'm flying, so  
the pressure recovery from the NACA duct must be pretty good.   
Actually, it is too much when it is below zero outside, until the  
pressurization kicks in.

On decent, it is easy to tell when the vent pressure exceeds the turbo  
output and the flapper opens with a pop.  If the flapper does not seal  
well, you will never pressurize.  It only takes a tiny leak to bleed  
off several psi.

Tom O
N241DM

On Apr 11, 2008, at 6:44 PM, Bill Wade wrote:

> I looked at the IV/IV-P Handbook but still have some questions-
>
> Does the NACA vent/blower provide good ventilation or would it be  
> wise to build in another source as well?
>
> Does the flapper valve do a good job of sealing the duct in  
> pressurized mode- especially if you change over in flight- or would  
> it be helpful to install a positive valve of some sort?
>
> Thanks very much-  Bill Wade  IV-P
>
> --
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