Pilots see static discharges dancing on their windscreens fairly often. As a passenger, you might be surprised or even concerned at the display. It can be very impressive, but it’s completely harmless. Let’s take a closer look at one of the coolest light shows that pilots experience on the flight deck!
As an aircraft flies through the sky, air and precipitation rub against the aircraft’s skin causing a buildup of static electricity. The same thing happens when you rub a balloon on your hair. When this electrical charge is strong enough, it can cause static on aircraft radios, interfering with communications. In typical conditions, the charge is continuously dissipated by small, pointed static discharge wicks mounted to the trailing edges of the wings and tail.
When aircraft fly through high altitude, ice crystals (cirrus clouds), heavy rain, or snow, the static discharge wicks don’t dissipate the precipitation static that builds up on the nose section of the aircraft. The static eventually discharges on its own, providing a fascinating web-like display on the windscreen.
St. Elmo’s Fire & BA Flight 9
St. Elmo’s fire is a type of luminous plasma discharge from a pointed object. This electrical discharge is called a corona discharge. It occurs spontaneously and naturally in fields that carry a high voltage. Contrary to popular belief, cockpit static discharges are not the same as St. Elmo’s Fire. Unlike the frequency of the cockpit window static discharge phenomenon, St. Elmo’s Fire is a very rare sight seldom seen by anyone, including pilots.
St. Elmo’s fire typically looks like a beam of bright blue light coming out from a pointed object, such as the nose cone or even the wing of an airplane. The color results from mainly the nitrogen and oxygen which our atmosphere consists of. The history of St. Elmo’s fire dates back to ancient Greek sailors. Hence, the glow was named after St. Erasmus, who is the patron saint for sailors.
In 1982, a British Airways 747 flew into a volcanic ash cloud from an erupting volcano over Jakarta. As a result, the aircraft experienced a quadruple engine flameout as a result of the volcanic ash building up within the engines. The immense friction from the ash particles in contact with the aircraft’s skin at high speed, created the St. Elmo’s Fire effect which, in itself, is harmless.
Unfortunately, as a passenger, you probably won’t see static discharges. If you are flying on a stormy night, however, you might catch a glimpse of St. Elmo’s Fire on a wingtip similar to the photo above. If you see it, be sure to take a photo because it’s certainly a rare catch!