What Should Pilots Do When Lightning Strikes?
Pilots are often faced with extreme weather patterns, such as thunder, lightning, wind, and more. While such flying conditions place fear in passengers, pilots are trained to act promptly, making quick maneuvers or abrupt touchdowns, if necessary. In this blog, we will cover lightning strikes in particular, diverting the fear and misconceptions associated with them.
Lightning strikes, though scary, do not pose a danger to the aircraft or passengers aboard. Even with direct lightning strikes, they do not penetrate the cabin or affect the engine and fuel tanks. In fact, when an aircraft is struck by lightning, the electrical charges travel the length of the fuselage and exit through the static wicks at the trailing edges of the flaps or tail.
To better understand why this happens, the analogy of the Faraday cage outlines this phenomenon perfectly. Faraday was a scientist who discovered that, if you place electricity through a metal cage, regardless of how strong or how high the voltage is, whatever is inside the cage will remain protected from the electricity. The airplane cabin is similar to the Faraday cage; thus, pilots and passengers are safe in the aircraft during a lightning strike. The plane itself may have some small burn marks on the fuselage skin at the point of impact, but no serious damage.
Upon landing, pilots must report the strike to engineers and a thorough inspection should be carried. This is important to keep in mind as each aircraft in the US commercial fleet is struck lightly by lighting more than once each year on average. Smaller business and private planes are less likely to be struck due to their size and because they generally avoid weather that is conducive to lightning strikes. This is wise considering aircraft can trigger lightning when they are flying through a heavily charged cloud.
In this instance, the lightning flash originates at the aircraft and extends away in opposite directions. Typically, the lightning attaches itself to an aircraft extremity, like the nose tip or wing tip. As the airplane flies through the lightning flash, the strike reattaches itself to the fuselage at other sections while the plane is in the electric “circuit” between the cloud regions of opposite polarity. The current will travel through the conductive exterior skin and structures and exit through an extremity.
Within the cabin, passengers and crew may see a flash of light and hear a loud noise. Pilots may report temporary flickering of lights or sudden interference with instruments, but nothing more serious than this. Careful lighting protection systems are engineered into aircraft and their sensitive components to ensure everything runs optimally.
Moreover, engineers design aircraft skin with aluminum, which is an excellent conductor of electricity. With no gaps or clearances in this conductive path, engineers can ensure that the lightning current will remain on the exterior of the aircraft. Some modern aircraft may be composed of advanced composite materials, which are not as conductive as aluminum.
Modern planes, such as passenger jets, have numerous computers and miles of wires that control many aspects of the aircraft. To protect them from damage in a strike, lightning protection engineers must ensure that surges or transients cannot reach the sensitive equipment inside the aircraft. These transients are called lightning indirect effects, and careful ground shielding, grounding, and surge suppression devices can mitigate the problems caused by them.
Another main area of concern is the fuel system, where even the tiniest spark can result in an explosion. With this in mind, engineers ensure that the fuel tanks are amply protected with a thick aircraft skin that can withstand extreme temperature fluctuations. Meanwhile, the structural joints and fasteners must be tightly designed to prevent sparks. Furthermore, access doors, fuel filler caps, vents, pipes, and fuel lines must also be protected. In the case of radar, conductive enclosures are not optimal; thus, diverter strips are applied along the outer surface of the radome to protect this area.
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