O corpo exterior condutivo
Quase todas as aeronaves têm corpos de metal, a corrente elétrica flui pelo metal exterior.
Aeronaves com casco composto podem ter materiais condutores adicionados aos compósitos para fornecer um caminho para o raio. Isso é tipicamente uma malha de metal.
Algumas aeronaves compostas menores, desprovidas desse tipo de provisão, simplesmente não podem voar perto de nuvens ou em qualquer lugar onde haja risco de raios.
foto da Boeing - veja as referências
A superfície condutora externa atua como uma gaiola de Faraday impedindo que as altas tensões e correntes afetem o interior.
uma foto de Faraday por Antoine Taveneaux
It is estimated that on average, each airplane in the U.S. commercial fleet is struck lightly by lightning more than once each year.
Initially, the lightning will attach to an extremity such as the nose or wing tip. The airplane then flies through the lightning flash, which reattaches itself to the fuselage at other locations while the airplane is in the electric "circuit" between the cloud regions of opposite polarity. The current will travel through the conductive exterior skin and structures of the aircraft and exit off some other extremity, such as the tail. Pilots occasionally report temporary flickering of lights or short-lived interference with instruments.
Every circuit and piece of equipment that is critical or essential to the safe flight and landing of an aircraft must be verified by the manufacturers to be protected against lightning in accordance with regulations set by the Federal Aviation Administration (FAA) or a similar authority in the country of the aircraft's origin.
De Scientific American - O que acontece quando um raio atinge um avião?
Planes are now built to absorb 250,000 amps, whereas the average strike generates 32,000 amps.
"It only gets really serious when the radome [nose cone] is struck, the only part of the plane's shell not made of metal, as this is where the radar is located. But nose cones have special lightning conductors for just this reason."
De The Guardian - Se você estiver preocupado com relâmpagos atingindo o seu avião?
The 787 flight test team gathered the unexpected data last month after one of the Dreamliner test aircaft was struck by lightning. Unlike traditional aluminum aircraft where the entire aircraft is conductive, on a composite airplane the charge from a lightning strike would find its way to the conductive parts such as wiring or hinges. In order to avoid the risk of the charge damaging these kinds of parts, Boeing had to add conductive material to the composites in order to provide a pathway for lightning strikes.
De Boeing 787 aguenta Lightning Strike
Outras referências