Safety

The three keywords for commercial air traffic are safety, efficiency, and environment. The local structure of the atmosphere in which the airplane flies is directly connected to safety. Accidents due to weather phenomena account for between 4 and 5% of the total number of accidents (Boeing source), and 5 to 7% domestic flight delays are due to meteorological causes, varying according to the season and the airport (Air France source).

For a flight of 1.5 to 2 hours' duration (gate to gate), accidents occur mainly during the takeoff and climb phases (more than 30%) and approach and landing phases (more than 50%). Some reasons are: at takeoff the aircraft weight could be at its maximum; rotation, the instant at which the pilot takes the initial climb attitude (angle of attack), corresponds to 1.3 V _ST (1.3 times the stall velocity); the landing phase implies a smooth junction between the airborne trajectory (altitude above terrain is related to barometric pressure) and the ground trajectory, which begins at the touchdown point; and atmospheric phenomena are more complex in the ground vicinity.

Until the 1950s, aircraft were considered as behaving like a rigid body; later, in flight, static deformations were included in the computation of the plane structure; the first two planes computed as deformable bodies were the B707 and the Caravelle, both introduced in 1958-1960. Nowadays, structural modes are taken into consideration at least up...