REFLECTOR: FUEL FEED & Vents

[Scott Derrick]

Scott,

An excellent answer.  I routinely run my tanks down to the 5-10 gallon 
range on a long trip. Extended descents, turbulence, steep turns that 
arn;t quite coordinated, will all unport a tank.  And whats gonna flow 
into the sump easier, air or fuel? 

I'll stick with the proven design.  Save my skin and Velocity's 
reputation...

Scott

Scott Baker wrote:

> Hello Keith,
>
> Regarding your question:
>
>> ..." I have never been able to identify a situation in which the sump
>> vent would do anything good for you (once the sump tank is filled the 
>> first
>> time).  Anyone got a scenario to the contrary?"
>
>
> I have wondered about a low fuel, prolonged descent with the nose 
> pitched down situation where the mains could become "unported".  If 
> this were to happen, and if the sump tank were not vented, then air 
> from the displaced fuel would be trapped inside the sump tank.  A 
> vented sump tank could easily purge itself and refill with fuel when 
> the aircraft reassumed a level flight attitude.
>
> The likelihood of unporting the fuel supply is not as rare as we might 
> think.  My older model C210 for instance, was placarded to warn the 
> pilot to land with at least one-quarter (1/4) tank of fuel to avoid 
> fuel starvation. Cessna designers installed two small "saddle tanks" 
> under the floor of the C210A the following model year.
>
> You pose a good question.  It's good to get a lot of clear thinking 
> heads to help brainstorm ideas like this before deciding upon a design 
> change - especially to something as important as the fuel system.  I 
> donno.  One thing I've learned about aviation is - whatever the 
> imagined unlikely event - it's probably going to happen!  Spins in a 
> Grumman with the wrong fuel tank selected = flameout.  Point my 1960 
> C210 downhill with low fuel = flameout.  Many twins call for the 
> selection of the "mains" for takeoff and landing to avoid the 
> possibility of fuel starvation.
>
> Just thinking out loud.
> SB
>
>
>
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