Lightning strikes on airplanes is a phenomenon that occurs with a relatively high frequency; and it is calculated that on average a commercial airplane will be struck by lightning every thousand hours of flight. Knowing that in 2019 there were more than 37 million flights in the world, according to data from the International Civil Aviation Organization, it can be estimated that around 300 planes are hit by lightning every day.
That is why one of the requirements taken into account when designing aircraft is the need to withstand the impact of lightning. But how do aeronautical manufacturers manage to make aircraft resistant to these meteorological events?
A physical explanation
The principle that makes aircraft resistant to lightning strikes is known as the Faraday cage. Michael Faraday was a 19th century physicist and chemist whose advances in electricity and magnetism have enabled significant achievements in science.
This scientist built the first Faraday cage in 1836. The cage consisted of a metal box that was placed in the presence of an external electric field and in which it was shown that the resulting electric field inside the box was zero. Since there is no electric field inside the cage, any object or device located inside will not be affected.
Applying this same principle to the aircraft, the outer skin of the aircraft will behave like a Faraday cage so that the interior of the cabin, the fuel tanks and the electronic equipment will be protected. For this, it is necessary that the outer surface of the plane is very good conductive, as is the case with the aluminum surfaces traditionally used in airplanes. In the case of the use of composite material, increasingly used in aeronautics, it is necessary to add metal meshes (usually copper or aluminum) that are added to the surfaces of these materials in order to improve electrical conduction. Finally, some electricity dissipaters are placed at the end of the wings allowing the energy received to be evacuated.
It is for all the above explained that passengers will most likely not realize that lightning has struck the plane in which they are traveling or, at most, they will perceive a rapid flash. From an aircraft operational standpoint, none of the flight systems should be affected and, if any damage occurs, it will be minor. Aeronautical operating protocols establish that when a lightning strike occurs, a ground control check must be carried out to confirm that the aircraft is able to continue flying.
Other examples of Faraday cages
This physical principle used in airplanes is also used in many other devices in our daily lives. Thus, microwaves also behave like Faraday cages. In this case, what is important is to protect ourselves from the high frequency radio waves that are used to heat the food. The walls of the microwave, made of metallic material, will contain the field generated inside and will prevent the exposure of said field from taking place outside the appliance.
Elevators are another everyday example that works on the same principle. These are usually made of metal forming a box that seals the interior from the external electromagnetic waves, a phenomenon that explains why on many occasions we cannot talk on the phone inside.
Finally we can talk about the example of cars and, more specifically, in the metallic chassis. When lightning strikes a car , the electrical energy will circulate on the surface as it happens with airplanes, so that, if we are inside with the windows rolled up, nothing will happen to us.
