When you were 5 years old and shuffled your feet across the carpet in anticipation of zapping your sister with an electrical shock, you were building up static electricity. Friction is an efficient way to help build the transfer of electrons, and thus static electricity.
Just as you shuffled your feet, an airplane also builds up static electricity as it flies through the air. We don’t think of a smooth aluminum surface as being a player in friction, but aircraft are subjected to huge amounts of it as they fly. That friction, in combination with the environment in which an airplane operates, means our little aircraft build up quite a lot of static electricity.
When it comes to staying safely in the air, none of this really matters. But most airplanes have miles of electrical wiring inside their skins, and sensitive electrical equipment such as the communication and navigation radios. A static wick works like your finger did to dissipate that electricity. Except instead of transferring it to your sister, it simply transfers it back to the atmosphere.
Static electricity isn’t the only reason airplanes have static wicks. They are also excellent at dissipating the electricity from a lightning strike, another reason aircraft usually don’t have to worry too much about such a thing.
The FAA’s aircraft certification regulations don’t require static wicks per se, but they do require a way to dissipate energy. In most cases, that means we have the wicks, which can be easily seen on the trailing edge of the wings and the empennage. In fact, you’ve probably been scraped by one already.
The static wicks are often riveted directly to the skin to make metal contact. They are generally wider where they connect to the airplane than at the end, which is why they’re also found on the trailing edge of aircraft surfaces. Electricity likes to collect near sharp edges.
If a wick breaks off it may not mean the end of the flight. Check to ensure the minimum equipment list doesn’t require them, and speak to a mechanic if in doubt.
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