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The information below is from the Shell Oil Company. Grounding is important
however it is more important that the two containers be electrically
connected, that is to say BONDED rather than simply grounded.
Ted Stanley
Q.Whenever fuel is poured, pumped or moved from one container to another, a
static charge is generated. The same principle is in effect when you walk
across a carpet in the winter and get a shock from a doorknob. The charge
level and the distance that can be jumped or arced depend on several
factors-pump rate, temperature, humidity and the containers. Static electricity is the reason why a ground wire is always connected to
commercial airliners and transport trucks whenever fuel is being
transferred. When you transfer fuel into your car or light aircraft, the
hose has a built-in ground wire that acts as an electrical path to
dissipate any static charge. As an added precaution, there is usually an
excessively rich air/fuel ratio in the fill pipe, which will not burn. There are two primary areas where a pilot should exercise caution when
transferring fuel. First is draining an aircraft tank. For example, if
you're draining a wing tank, you should always connect a jumper cable from
the plane to the fuel container. This will dissipate the charge and
eliminate the chance of a spark jumping from plane to container, causing a
fire. Remember when you're draining fuel, there can be enough air
circulation so that the air/fuel ratio is in the burnable range. The second area of concern is the filling process. Many FBOs use a ground
wire when filling an aircraft. But in some cases, fuel is transferred from
a drum or can into an aircraft. Here, a jumper wire is a good safety
precaution to ensure that the charge is dissipated. If you use a metal
funnel with metal cans, make sure that the can, funnel and plane are always
touching during transfer. With metal containers, the electrical charge is dissipated to the
conductive container where it can be discharged by a ground wire or
contact. In plastic containers, there is no good electrically-conductive
path to dissipate the charge. Although some people put metal strips into
the plastic container, I would recommend the use of metal containers with a
good jumper wire. It's the safer way to go.
LML website: http://www.olsusa.com/mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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