REFLECTOR: Grounding Point

[Scott Derrick]

Jim, heard you had an unfortunate cylinder failure?

All OK now?

Scott

At 03:49 PM 10/28/2004, you wrote:
>My fuel caps are fastened by a 6"-8" chain to the apex of a 3" x 1.5" 
>triangular piece of Al to prevent the cap from departing the airplane 
>(through the prop :o).  I fastened another 12" piece of chain to the 
>center of the base of the cap retainer so it dangles to the bottom of the 
>fuel tank.  The retention mechanism cannot but be in contact with the 
>metal filler neck, nor can the fueling nozzle.  I just clip the ground 
>cable to the chain.
>Added a little hunk of chain to the mandatory cap retention mechanism .... 
>Jim S.
>
>Gilles Gratton 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: <mailto:reflector-bounces at tvbf.org>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 <mailto:cjensen at dts9000.com><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: <mailto:reflector-bounces at tvbf.org>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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