I could care less if the airplane wing and nozzle are at ground, just that they are at the same potential before fuel flows or caps are removed. So if it's a fuel truck on rubber wheels or a stationary fueling island, the clamp needs attached first. Then, I still want to see the closed fuel nozzle touching the wing skin before the cap is removed.
I don't think that your assumption was wrong. There might be a charge on the airplane or fuel truck. The fuel contacts the metal nozzle after passing through the filter. But who has ever seen a lineman blasted or running across the tarmac on fire screaming, "Gee, I wonder what caused that static discharge?"
Many small airports don't even carry Jet A. Even if they do, the fuel trucks and delivery rates are similar. Here again, you won't see them gounding anything, but just attaching a clamp from the truck to the aircraft.
Joe
