REFLECTOR: Fuel venting issue

[Brett Ferrell]

There was a ATP incident where the wing tanks crushed due to blocked 
vents that I've posted previously, but here is a different article from 
ASF, and a quote "/On some Cessnas there is also an alternate vent in 
the fuel cap that opens to allow air through when a vacuum is applied to 
the tank/"
http://www.aopa.org/asf/asfarticles/2003/sp0305.html
http://www.faa.gov/ats/afss/newyork/ACFTOPS.htm

B

Scott Derrick wrote:
> these valves are made for liquid.  one way valves can seep a bit, and 
> you would never know, except in this case... its only held closed by a 
> very small spring.
>
> I'm trying to think of another plane that has a fuel vent open to the 
> cabin and can't.  The failure mode of  this valve is potentially  
> catastrophic!
>
> Anybody know of any certified or experimental plane that has this 
> configuration?
>
> Was this added because somebody crashed?
>
> Can Scott Baker explain the reasoning behind this change to the plans 
> and why Velocity thinks this is a safe thing to do?
>
> Scott
>
> Brett Ferrell wrote:
>> Then it's a good thing it's not open to the cabin.  The check valve 
>> only allows air from the cabin into the tanks....
>>
>> B
>>
>> Scott Derrick wrote:
>>> I have a hard time feeling good about having a fuel vent line open 
>>> to the interior of the cabin...
>>>
>>> Scott
>>>
>>> Alex Balic wrote:
>>>> The check valve is located inside the plane and above the level of the fuel
>>>> in the tanks (right up at the roof- it T's into the vent system, so fi the
>>>> external vent fails, it will open and allow air into the tanks from the
>>>> cabin- but not let fuel/fumes out into the cabin.
>>>>
>>>> -----Original Message-----
>>>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>>>> Behalf Of David Staten
>>>> Sent: Sunday, July 01, 2007 12:49 PM
>>>> To: Velocity Aircraft Owners and Builders list
>>>> Subject: Re: REFLECTOR: Fuel venting issue
>>>>
>>>> If the check valve is on the same line that is theoretically blocked by 
>>>> ice or mud, how is it able to prevent ANYTHING? An obstructed vent is an 
>>>> obstructed vent.
>>>>
>>>> Dave
>>>>
>>>> Brett Ferrell wrote:
>>>>
>>>>   
>>>>> The check valve is actually there to prevent tank collapse should the 
>>>>> vent line become blocked (by say a mud-dauber or ice accumulation).  
>>>>> I've seen a 15,000 gallon steel tank collapse by a plugged vent, and 
>>>>> it's not pretty...
>>>>>
>>>>> B
>>>>>           

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