AVIATION
Do Airplanes get hit by Lightening in the Sky?
There are two types of electricity: dynamic, involving moving currents used in daily life, and static, a stagnant current potentially hazardous for aviation.
When embarking on flights, you likely observe the small rods extending from the trailing edges of aircraft wings. While some may mistake them for antennas or sensors, they serve a crucial purpose known as ‘Static Wicks.’ Understanding static electricity is essential before delving into static wicks. There are two types of electricity: dynamic, involving moving currents used in daily life, and static, a stagnant current potentially hazardous for aviation. Static electricity results from the attraction of unlike charges due to friction.
What is Static Electricity?
Everyday scenarios, such as rubbing a comb through hair, demonstrate static electricity. When you rub your shoes on the carpet, your body accumulates extra electrons, leading to a shock when touching objects. In the context of aviation, static electricity can pose problems, interfering with electronics, communication systems, and navigational equipment. To mitigate these risks, aircraft are equipped with safety features like static dischargers (wicks), lightning protection, and grounding.
One significant threat is lightning strikes during flight, capable of disrupting the aircraft’s electrical and communication systems, potentially causing irreparable damage. Static wicks play a crucial role in preventing such issues. They feature a sharp carbon point, creating a gradient that facilitates the release of static charge into the atmosphere, reducing radio interference and surface charge accumulation. However, wicks may not completely discharge an aircraft, emphasizing the need for earthing during refueling on the ground.
Understanding the science behind static electricity distribution is crucial. Uniform or blunt surfaces distribute charges evenly, while pointed or irregular surfaces accumulate charges. Static dischargers on aircraft, positioned on aerodynamic surfaces, have pointed ends. As the aircraft interacts with atmospheric particles during flight, friction induces static electricity, which is then discharged through the wicks into the atmosphere. On the ground, most aircraft discharge static electricity through the nose landing gear.
In the rare event of a lightning strike, static wicks ensure the safe discharge of high voltages, although they may melt or burn. These wicks are strategically placed on control surfaces like ailerons, flap track fairings, rudders, and elevators.
Distinguishing static discharge from St. Elmo’s Fire is crucial. While static wicks handle typical static discharges, St. Elmo’s Fire is a rare phenomenon involving a bright plasma discharge from pointed objects. It appears as a blue light beam, often seen on the nose cone or wingtip during storms. St. Elmo’s Fire is distinct from cockpit static discharges, and witnessing it, even for pilots, is infrequent.
The BA Flight 9 incident in 1982, involving a British Airways 747 encountering volcanic ash, produced St. Elmo’s Fire due to intense friction with ash particles. Generally uncommon during travel, capturing a photo of St. Elmo’s Fire on a wingtip during a storm is a unique opportunity.
