Every second, 50 to 100 lightning discharges develop in the atmosphere. Much of this electrical activity takes the form of lightning "intra-cloud" that spread inside the cumulonimbus, usually between 5 and 10 km altitude.
They indicate a risk potential for civil and military aircraft and space launchers. This risk is far from being marginal, since a commercial airliner is struck by lightning on average every 1500 hours of flight.

Protection standards stringent

The devices must meet the stringent standards of protection, especially since the development of composite structures and digital systems in principle, increases their vulnerability. The research conducted at ONERA dual objective optimization methods to protect and improve the representativity of qualification testing laboratory.

The camera fires the flash

During the 80s, the implementation of campaigns flight tests on aircraft instrumented was a milestone for approaching the overall phenomenology of lightning. In particular, it has been demonstrated that the device itself triggered the lightning crossing regions where cloud reign ambient electric field Eo high.

- Over 90% of cases, the device activates itself by developing a flash from the point of maximum amplification electric field surrounding two rising ionized channels in virgin air. One of these sites is spreading in the direction of the ambient field (discharge "positive"), the other in the opposite direction (discharge "negative") together constitute the initial phase called "precursor" or "leader" . The channels are developing several miles at a speed between 10 and several hundred kilometers per second. The current, initially consisting of series of pulses, usually evolves to a continuous level of several hundred amperes.

- In these channels, then move at regular intervals, high current pulses of a few tens of Kiloampere. These phenomena of sudden reactivation of the channel are called "dumps junction" or "recoil streamers".

Identifying areas of impact points of lightning

The introduction of the physical laws of the boot allows the determination of preferential points of entry and exit of the current on a plane or a helicopter, for different amplitudes and directions of the ambient field.