Have you ever looked at the back of a plane wing and seen a row of small metal spikes? They’re officially called static wicks, and they play an important role in keeping your flight safe. But, what are they exactly?
Well, these small needles discharge static electricity. Without them, the build-up of static electricity could cause some serious problems! Often falsly compared lightning conductors, static wicks are not actually used for lightning protection. Infact, if an aircraft is hit by lightning, they will often burn up and fall off!
Here’s a brief overview of what those little metal rods protruding from the aircraft wings are, why they are needed, and how they work!
Why does a plane need spikes on the wings?
A plane requires static wicks to help it combat a byproduct of flying through the atmosphere — static electricity. Have you ever rubbed a balloon against a wool jumper, or shuffled along thick carpet, then noticed a small sharp shock when touching something? That’s static electricity, a by product of the friction generated by rubbing the material together.
When aircraft speed through the air, a similar effect occurs along the fuselage, with static electricity gradually accumulating on the outer surface.
When static builds up, it can cause all sorts of problems:
What would happen without static wicks?
Without static wicks — sometimes referred to as static discharges — the aircraft would gradually attain an increasing static electric charge as it passes through the air. When flying through air with precipitation, such as ice or rain particles, this static charge can increase even more rapidly through a process known as triboelectric charging.
This charge cannot build up forever, and once the charge is large enough — based on a range of factors — it will look to discharge itself back to the surrounding atmosphere. The charge will look for the easiest route. This is usually the thinnest part of the aircraft, such as the wingtips and tailplane. The resultant discharge of energy can result in a loud bang, heating, and even visible sparks.
How do static wicks work?
Static wicks are typically made of a combination of graphite, and conductive metal, typically copper or aluminium. They’re placed at key points on the wing, like the wingtips and trailing edges.
They are designed to be more attractive to static energy, than any of the other aircraft extremities such as antenna, wingtips, or flight controls. As the plane moves through the air, the wicks help to discharge any static electricity that has built up from the friction of the plane moving through the air.
By providing an easy route for static electricity to flow out from the aircraft, static discharges continuously allow static to dissipate back into the atmosphere. They ensure that the aircraft’s static build up is minimal, preventing the large build up of charge, and the subsequent uncontrolled static shock discharge.
Do all planes have static wicks?
Yes, all commercial aircraft have static wicks. They’re required by aviation authorities, such as the Federal Aviation Administration (FAA) in the USA or EASA in Europe, to get a plane’s certification.
Before each flight, pilots will check the static wicks during their walk around, ensuring there are sufficient numbers remaining. Any broken or damaged static discharges are noted and engineering will replace them.
What happens if a static wick falls off?
If a static wick falls off, it’s not a huge deal. As they are deliberately slender, and attached to the extremities of the aircraft, it’s actually fairly common for them to become loose and fall off during flight.
Equally, while static wicks aren’t designed as lightning rods, when aircraft get hit by lightning it is pretty common to find many of the metal rods charred and damaged.
There are normally around 15-20 static wicks on all commercial aircraft. This is a significantly higher number than required, ensuring that in the case of damage, there is always a sufficient number to perform their task correctly.
Rarely, this can mean that aircraft might even begin a flight without all the static wicks. Commercial aircraft can fly with some static dischargers missing for a set number of flights before they are required to be replaced.
So, there you have it — the mystery of the static wicks solved! Now you know just what those metal rods are and why they’re on plane wings. Next time you fly, take a look out the window and see if you can spot them attached to the back (trailing edge) of the wing!
When static electricity builds up on an object, it looks for the quickest way to dissipate. Aircraft collect a static electric charge while flying through the air. The metal rods on the wings provide a gradual low-resistance path, so the static discharges through them continuously.
This keeps the charge on the airframe from building up to dangerous levels, and dissipating with a bang.