Lightning protection of aircrafts

When you fly to the East, it gets dark quickly. Landing in Surgut was in complete darkness. It was light only dead ahead. Continous lightning flashes meant there was a thunderstorm front near. The passengers sighed when the undercart finally touched the concrete slabs of the runway. Flights furing a thunderstorm are a must-have element of almost each adventure movie or fiction. This is quite consistent. A modern aircraft meets a lightning every 2000-3000 flying hours. It is not a rare thing to meet lightning, especially if to consider that there are thousands of large aircrafts in the sky around our planet every day. The accidents are rare, because a modern air plane is quite resistant to lightning and is able to stand attack of a powerful lightning discharge. Even an amateur will notice a different approach to lightning protection of air crafts and onground facilities. Lightning can be averted from any facility on the ground surface with the help of lightning rods. But you cannot put a lightning rod near an aircraft in the sky. It wo't make sense if to install it on the nose or on the tail of the airplane. Lightning current, captured by a lightning rod, will still flow along the fuselage and all the possible troubles will happen. It is reasonable to study the mechanism of a lightning strike into an airplane in a more detail and clarify the consequences of such a strike.

1. The mechanism of lightning attraction to an airplane

We must start with a hypothesis of Gold. Almost half a century ago, he quite reasonably supposed that a plasma channel, forming from the top in the electric field of the atmosphere predetermines the point of a lightning strike into an on-ground structure.

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2. Start of lightning from air crafts

It is ascertained that with the increase of the object height above 200 m, the number of downstream lightnign strikes into it (they start from a thunderstorm cloud) do not increase. But the number of upstream lightning, which originate from the structure's top and uprush to a thunderstorm cloud, increases.

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3. Detector of a thunderstorm danger

Why not to try and make a board instrument to control electric field on the flight course? There are no serious problems with the measuring. Modern gauss meters (the detectors of electric field) are able to measure the electric intensity from units of volts per meter. The problem is not in measuring but in the representation of the results obtained.

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4. Danger of a direct lightning strike

One, imagining a graceful construction of a modern airplane fuselage with a thin dural or titan cover, thinks about the thermal impact of powerful lightning strikes. In fact, their real danger is not that great.

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5. Airplane electrization charge

Have you ever stroke a cat in a dark room? On a frosty winter evening, you will see weak blue sparks under your hand. It is a frictional electrification. An airplane is not a cat, but at a high speed, it gets electrified as well. It happens because of mechanic microinclusions and hydrometeors in the air, able to split the charges at the friction against the fuselage surface.

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6. Electromagnetic disturbances from lightning current

For a modern airplane, it is, probably, the most dangerous lightning impact. Any driver knows well about the duplication of mission-critical control systems. This is why, the hydraulic power of the breaks is split into front wheels and rare wheels. Damage of one system doesn't disturb the operation of the other one. Duplication of hydraulic systems is used in the airplanes. Electrical system can be duplicated, but with one significant stipulation.

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7. Tests for lightning resistance

According to the rules of the international aviation organization ICAO no aircraft can be used for passenger transportation without detailed tests for lightning resistance. Their method imitates the consequences of a direct lightning strike with ultimate parameters on an aircraft. The requirements to the test procedure are so strict, that their organization still creates problems, and the results are not always treated unambiguously.

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8. What do composite materials promise

The prospect of their use in aviation promises bright outlooks to everybody, except specialists on lightning protection. Cheapening and weight-reduction of the air frame construction doesn't cause any doubt. As for lightning protection, it is not that clear.

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