Cockpit window static discharge is something that airline passengers don’t get to experience.
And that’s too bad. You are indeed missing out on a spectacular sight!
Watching this static discharge dancing across the windows of the flight deck is a fairly frequent experience for airline pilots.
Before you panic
Your initial reaction learning about this may be with concern or even fear but relax.
Static discharge is not dangerous. As a matter of fact, it’s totally harmless!
Let’s look further into this stunning show of display that pilots sometimes get to enjoy…
What causes Cockpit Window Static Discharge?
In simple terms, it’s caused by a large amount of static electricity buildup around the windows.
The buildup, in turn, causes an electrical discharge.
That electrical discharge then manifests as a light-show on the window surface.
Can you explain this further?
First, an easy to imagine scenario:
We have all experienced static discharge in our daily lives.
These discharges can be seen as “sparks” in a dark room, they are heard as a crackle-sound, and they come with an “electrical” smell.
Let’s say you remove your blankets from your dryer after wash and dry.
You forgot to insert a dryer sheet prior to dry to avoid static cling.
Now turn off the light and shake your blanket.
As the excess static discharges, you can see the harmless sparks, hear the sound of the discharge, and sometimes smell the electrical reaction.
Now to your airplane:
Static electricity builds when an airplane is flying through the sky.
The static electricity is caused by the air and precipitation which surrounds the airplane. The air and precipitation are constantly rubbing the skin of the airplane, causing friction.
The friction, in turn, creates an electrical charge, or static electricity.
Precipitation consists of rain, snow, ice, or dust particles.
Why doesn't static discharge show in cabin windows?
Cockpit windows face the oncoming wind and surrounding particles head-on, creating a rapidly producing discharge friction effect.
Cabin windows are on the side of the airplane, causing less friction, which is not enough to produce the static discharge effect.
Static Wicks minimize the effects of static discharge
Airplane wings static discharge wicks.
Static dischargers, also called static wicks or static discharge wicks, are installed on the back of the wings and the tail.
The static charge is continuously eliminated with the help of the small. pointed wicks.
The wicks prevent problem-free operation of radio communications equipment and onboard navigation electronics during precipitation. This disturbance is called precipitation static, or p-static.
The static wicks are designed to discharge the static (electrical friction) buildup into the air.
The charge is discharged through the wicks because they contain sharper metal points than what is found anywhere else on the airplane.
The wicks will not work unless they are properly bonded to the airplane.
Every part of the airplane must have a conductive path to the dischargers. Otherwise, they would be useless.
Although the wicks are mounted on the wings and on the tail the origins of the path are located on every door, access panel, navigation lights, antennas, cowls, control surface, and in other places.
How long have airplanes had static wicks?
Military airplanes were the first to be equipped with static wicks during World War II in the 1940s.
A joint Army-Navy team, led by Dr. Ross Gunn of the U.S. Naval Research Lab came up with the discovery, then installed the static wicks on military aircraft.
Why do the windows spark if we have static wicks?
The majority of the airplane skin is connected to the static wicks.
Metal is needed to create a bond or a connection for electrical continuity, such as the static discharge system.
The windows are made from a glass-type, and they do not bond or connect with the static wicks.
Therefore the precipitation static build-up on windshields is not neutralized by the static wicks.
Precipitation static is produced from things like clouds, heavy rain, and snow.
Therefore, the window precipitation static is left to discharge on its own.
Cockpit Window Static Discharge for You to see!
The video shows static discharge in the cockpit windows of a Boeing 767. This clip was filmed while I was on the cockpit jump-seat of a South American airline en route to Buenos Aires, Argentina.
There were plenty of highly charged thunderstorms in this area, located above the Andes Mountains on a “red-eye” summer night flight.
Play the video below
Cockpit Window Static Discharge Video B767 © 2008 Captain Les
St. Elmo's Fire
There is another phenomenon occurring in the air, which is often confused with window static discharge, because of its apparent similarity in visual presentation.
This other phenomenon is called St. Elmo’s Fire.
St. Elmo’s Fire will be discussed in my next article, to be published in January.