REFLECTOR: Fuel Flow Rate

Brett Ferrell reflector at velocityxl.com
Fri Jun 23 16:25:32 CDT 2006


Pat - I'm simply aghast.  ;-)

Actually, I think I said it would *probably* be OK, but didn't want to try 
it, but I appreciate the data, that makes me feel better.  As I say, I'd 
worried ever since seeing a steel tank crushed at work, and reading about 
accidents like this one:
http://www.aopa.org/asf/asfarticles/2003/sp0305.html

Glad to hear that it probably won't affect any of us.

Brett

----- Original Message ----- 
From: "Pat Shea" <xl340hp at yahoo.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Friday, June 23, 2006 4:19 PM
Subject: Re: REFLECTOR: Fuel Flow Rate


>- Scott Derrick <scott at tnstaafl.net> wrote:
>
>> Hmmm..  I wonder?
>
> -- alventures at cox.net wrote:
>
>>> Not to worry.  Vapor lock would occur long before
>>> the sump would be damaged.
>
> --- Chuck Harbert <c.harbert at comcast.net> wrote:
>
>>>> I now also think that it would be a bad idea not
>>>> to vent the sump because you could collapse it >>>
> from the suction of the pump.
>
>
> If you cap off the sump vent line the sump can still
> vent via both fuel strake vents. In this
> configuration, there is a "suction" scenario where
> nearly empty strakes can't keep up with sump's gravity
> flow rate - but the resulting slight vacuum in the
> sump is certainly nothing that's going to compromise
> the structural integrity of the sump.
>
> I performed the following extreme test ('cause I
> wanted to know): I capped off ALL three vent lines and
> let the fuel flow out downstream of the sump until it
> stopped. I then turned on the electric fuel pump and
> sucked 4 gallons of fuel out of the system.  I had
> tapped a vacuum gauge into the system which read about
> 3.5 in/hg. I'd estimate this is 5-10 times more vacuum
> a sump would see just from being non-vented. Brett is
> cringing right now...
>
> This scenario is comparable an airplane (say a spam
> can) where a vent line becomes fully obstructed and
> the mechanical or electric fuel pumps suck fuel from a
> tank until they just can't suck no more. Of course,
> Velocity's are a step ahead in this regard since we
> have an alternate fuel vent line w/ a check valve.
>
> However, vapor lock is a whole other issue whenever
> your sucking fuel. Oh, and then there's the sump air
> pocket from un-ported strake pickups to deal with
> too...
>
> Pat
>
>
>
>
>
>
>
>
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