Staying grounded – the importance of grounding while refueling

Grounding an aircraft when refueling is a safety measure to prevent any electrical current from creating a spark that could ignite the fuel. The grounding process creates an electrical connection between the aircraft and the ground, which neutralizes any static charge that may have built up on the aircraft’s surface. This ensures that any fuel that may accidentally come into contact with an electrical source will not ignite. Additionally, grounding the aircraft also helps to prevent fuel spills and leaks by ensuring that the aircraft’s fuel system is properly grounded and not damaged.

The flow of fuel in the fuel hose and inside the aircraft creates static electricity. If the static isn’t discharged by proper grounding a spark can be created between metal parts as the static is looking for a discharge point. Of course, a spark can cause an explosion. It’s a bigger hazard in avgas equipment due to the volatility of gasoline but even jet fuel can ignite even though it’s not as volatile.

At large airports that serve airlines, they used to connect a ground cable from the pumping unit to the aircraft and another cable was connected to a grounding point. But there was a problem: many airliners were refueled in inclement weather. If lightning should strike the jet during refueling, the path to the ground could increase the damage to the airliner, especially to the electronics.

A number of years ago the airline industry changed its fueling procedure, eliminating the second ground cable that connected the refueling unit to a ground terminal. Now, they just connect the aircraft to the refueling unit in a process called bonding.

When refueling an avgas-powered aircraft, a grounded hose is also used. But avgas has a lower vapor pressure than mogas and refueling is usually in a higher air current area. This means that the nozzle to the tank neck has a greater possibility of being in the right air-to-fuel ratio to support combustion. For safety’s sake, a ground or bonding connection is required to dissipate the charge. One of the biggest concerns for general aviation aircraft is where to connect the grounding or bonding cable. On some certified aircraft, there is a designated grounding terminal. Usually, it is on the landing gear, but sometimes it is on the exhaust.