REFLECTOR:RE:check valves

[Pat Shea]

The current vent system: All three tanks vented thru a
common manifold mounted high up on the forward side of
the firewall.  

The only benefit I see from the check valves between
the mains and the sump is preventing the transfer of
fuel from one main tank to the other. Although this
can happen, as the factory demonstrated w/ a 'rigged'
cap, one of the caps REALLY needs to be leaking. 

They are not going to help one of the issues that
started this thread which is uneven fuel flow from the
mains and the resulting useless fuel in the fuller
tank when the lower tank runs dry. Al's analysis of
the head pressures involved is right on. The current
gravity system is simple, just not very positive. The
last time this thread went around someone suggested
placing electrically operated valves between the mains
and the sump. The valves would require power to close
and failed open. The idea was that these valves could
be used to manage uneven fuel levels. Of course they
add both fuel management complexity and additional
failure points to the fuel system... 

In terms of the sump fuel warnings - has anyone looked
(or had someone else look) at the sump fuel level in
flight while the warning light is coming on? It might
help the discussion if we actually knew there was air
in the sump, how much, and in when. I suspect this is
more of a sensor issue than a safety one.

Pat

--- alventures <alventures@msn.com> wrote:

> Before analyzing what might be bad about the idea,
> I'd be interested in
> knowing what benefit there could be.
> 
>  
> 
> Al




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