REFLECTOR: Grounding Point

[Jim Sower]

<...not any way for the charge to pass to the chain ...>
So how does it get go ground on a Cessna or RV?

BTW, in the interest of perspective or context, does anyone on this list 
have first-hand (saw it happen) or second-hand (personally knows a 
reliable first-hand witness) of a refueling fire caused by static charge 
on ANY airplane?  Or automobile, for that matter?

Inquiring minds need to know ... Jim S.

Alex Balic wrote:

>the fuel itself is non conductive, it is the charge that is stripped from
>the surface of the flowing fuel that builds up on the surface of the skin
>and metal parts that causes the problem, the metal chain in the fuel trick
>is not effective, since there is not any way for the charge to pass to the
>chain.
>
>-----Original Message-----
>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
>Behalf Of Scott Derrick
>Sent: Sunday, October 24, 2004 4:56 PM
>To: Velocity Aircraft Owners and Builders list
>Subject: RE: REFLECTOR: Grounding Point
>
>
>If an airplane has capacitive fuel sensors,  Doesn't that provide a ground
>path from the fuel in the tank to the exhaust pipe?
>
>Scott
>
>At 02:16 PM 10/24/2004, you wrote:
>  
>
>>We are talking retrofit here.  My plane has been flying (and refueling) for
>>4 years and I only clip the grounding cable to the nozzle for lack of a
>>better grounding point.  However I like the screen bit.  Would it work if
>>one was to shape a cylindrical screen that could be inserted in the fuel
>>    
>>
>cap
>  
>
>>opening at every fuel stop.  This cylinder could reach the bottom of the
>>tank and have a flange that would barely touch the top strake around the
>>fuel tank opening. The fuel nozzle would then  flow through that screen.
>>The only draw back would be to carry (and store ) this contraption to have
>>it on hand at every refueling stop.
>>Gilles
>>
>>-----Original Message-----
>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
>>Behalf Of Jim Agnew
>>Sent: 24 octobre 2004 14:43
>>To: Velocity Aircraft Owners and Builders list
>>Subject: RE: REFLECTOR: Grounding Point
>>
>>
>>The concept of a fire screen has been proven for many years in miners
>>    
>>
>lamps.
>  
>
>>A
>>fine mesh screen tube surrounding the filler inlet that goes to the bottom
>>of
>>the tank will prevent the passage of the flame front into the fuel tank
>>    
>>
>even
>  
>
>>if
>>the fuel vapors inside the fire screen tube ignite.  This screen does not
>>depend on grounding.
>>
>>Jim
>>
>>
>>--- Chuck Jensen <cjensen at dts9000.com> wrote:
>>
>>    
>>
>>>Mmmmmm. Alex's idea of first checking for continuity between the fueler
>>>      
>>>
>>ring
>>    
>>
>>>and the exhaust pipe is a good one.  If there is continuity, then
>>>      
>>>
>>executing
>>    
>>
>>>Al's idea of a drooping chain from the cap down into the fuel seems to
>>>assure there is a fuel-chain-exhaust-refueling stating ground (all this
>>>assuming there is fuel ring to exhaust continuity).  Richard's method,
>>>      
>>>
>>from
>>    
>>
>>>a Very Large Aerospace Company, appears to do the same thing, just
>>>      
>>>
>better
>  
>
>>>and with a higher degree of certainty.  Of course, if there's not
>>>continuity, then its back to the drawing board.  It's somewhat
>>>      
>>>
>comforting
>  
>
>>to
>>    
>>
>>>know that the incidence of Velos going off like Roman Candles is rare,
>>>      
>>>
>but
>  
>
>>>I'd hate to be the first data point.
>>>
>>>Chuck
>>>
>>>-----Original Message-----
>>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
>>>Behalf Of Richard Riley
>>>Sent: Sunday, October 24, 2004 11:44 AM
>>>To: Velocity Aircraft Owners and Builders list
>>>Subject: RE: REFLECTOR: Grounding Point
>>>
>>>
>>>We went around and round on this topic on one of the canard mailing
>>>      
>>>
>lists
>  
>
>>a
>>    
>>
>>>few months ago.  Following all the suggestions, I talked with a fuel
>>>      
>>>
>>system
>>    
>>
>>>designer at the Very Large Aerospace Company where I work and came up
>>>      
>>>
>with
>  
>
>>>the following for my plane...
>>>
>>>The fuel cap ring is attached to a coarse brass screen, shaped in a
>>>      
>>>
>tube,
>  
>
>>>that goes from the fuel cap ring to bottom of the tank.  It is attached
>>>      
>>>
>by
>  
>
>>>a brass ball chain to the fuel drain, and to a brass bolt in the
>>>      
>>>
>outboard
>  
>
>>>fuel bulkhead.  That bolt is then attached by a wire to the engine, and
>>>therefor to the exhaust pipes.
>>>
>>>Most of the static charge in refueling is created by the fuel falling
>>>      
>>>
>from
>  
>
>>>the nozzle to the surface of fuel in the tank.  The brass screens strips
>>>that away.  No matter what the level of the fuel, it's pierced by the
>>>      
>>>
>>chain
>>    
>>
>>>going to the fuel drain.  And then the whole thing is electrically
>>>      
>>>
>bonded
>  
>
>>>to the engine block.  If the fuel truck attaches the ground strap to the
>>>exhaust pipe, all the potential is equalized.
>>>
>>>
>>>At 09:21 AM 10/24/04, Al Gietzen wrote:
>>>      
>>>
>>>>I guess there are different views on this, but I see little relation
>>>>        
>>>>
>(as
>  
>
>>>>in maybe "none") between grounding the exhaust pipe, and refueling
>>>>safety.  The static charge buildup is between the nozzle and the fuel
>>>>(surface); or the nozzle and the potential existing static charge on
>>>>        
>>>>
>the
>  
>
>>>>surface of the strake due air friction.  So have a metal chain or cable
>>>>        
>>>>
>>>>from the cap ring hanging into the fuel, and keep the nozzle against
>>>      
>>>
>the
>  
>
>>>>ring; and, if you have just landed, wipe the surface of the strake with
>>>>        
>>>>
>a
>  
>
>>>>damp cloth before contacting the nozzle to the ring.
>>>>
>>>>Anyway, that's my take; but I've been wrong once before in my lifeJ.
>>>>
>>>>Al
>>>>Subject: REFLECTOR: Grounding Point
>>>>
>>>>I didn't find a direct reference in the archives, so I was still
>>>>        
>>>>
>>wondering
>>    
>>
>>>>if the exhaust pipes is an adequate grounding point when refueling?  I
>>>>always assumed it was but I'd hate this to be a FireBall Falacy.
>>>>
>>>>Chuck
>>>>__
>>>>

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