[Article déjà publié le 1er décembre 2024]
On a plane map, air journeys between two cities often seem to follow improbable, almost counter-intuitive curves. However, these curves are the manifestation of a very real phenomenon: the geometry of a globe. Between geographic constraints, a rigorous organization of airspace and adaptations to meteorological vagaries, the trajectory of planes obey specific principles, far from being dictated at random. But why does a straight road on a map not correspond to the shortest distance in the sky?
An illusion of curved trajectories
The Planes cards, such as Mercator's projection, are at the heart of the misunderstanding linked to the trajectories of the planes, notes Iflscience. This method of representation, widely used, distorts proportions and distances, particularly by moving away from the equator. A straight line on this map does not correspond to the shortest distance on a sphere.
The planes generally follow the orthodromic road, drawn according to the principle of the large circle. This trajectory represents the shortest distance between two points on a sphere, unlike the loxodromic road, which maintains a constant course but considerably extends the distance traveled.
A famous example illustrates this reality: thefts between Europe and the United States often pass near Greenland. Although it seems to be a detour on a flat card, it is actually the most direct path. This choice saves time and fuel, while respecting operational constraints.
Air roads, a sky organized for safety
The sky is not a free space where planes can fly without restrictions. Since the beginnings of commercial aviation, air roads have been defined to organize traffic. These virtual corridors are made up of fixed points called tags or intersections, which planes must respect.
These roads help manage ever denser air traffic. They thus limit the risk of collision. In addition, they facilitate the work of air controllers. Around large airports, specific rules apply. For example, Sids organize takeoff. In parallel, the stars structure the landings. These measures optimize traffic while reducing nuisance for residents, as Dataero points out.
In some areas, such as Europe, the concept of Free Road Airspace (FRA) allows greater flexibility. Pilots can choose their own routes between two virtual points, thus optimizing their journeys. However, this freedom remains strictly supervised to guarantee security.
The weather, an essential constraint for the aircraft trajectories
The weather conditions directly influence the aircraft routes. Thunderstorms, in particular, represent a major risk. Turbulences, lightning and strong winds can compromise security. The pilots are therefore trained to bypass these dangerous areas, even if it means lengthening the journey.
In polar regions, solar storms represent another threat. These phenomena, caused by an intense magnetic activity of the sun, can disturb navigation and communication instruments. The planes that fly over these areas must sometimes adapt their altitude or their route.
The wind is also a key factor. The currents, these fast winds at high altitude, are often exploited to accelerate journeys in a given direction. However, when they blow in the opposite direction, they slow down planes, sometimes forcing to adjust the route to limit their impact.
Optimization between efficiency and economy
In addition to geographic and meteorological constraints, airlines are constantly looking for optimization. The fuel consumption, the main expenditure post of operators, guides a large part of the decisions related to the routes.
Modern navigation systems, such as GPS and inertial systems, make it possible to calculate in real time the trajectories of the most effective aircraft. These technologies, combined with constant updates of air roads, offer pilots efficient tools to adjust their flight plans according to conditions.
Adjustments called “direct” can also be authorized by air controllers. These shortcuts, which consist in jumping several points from an air route, significantly reduce the flight time and the environmental impact, while respecting safety standards.
With an unwavering passion for local news, Christopher leads our editorial team with integrity and dedication. With over 20 years’ experience, he is the backbone of Wouldsayso, ensuring that we stay true to our mission to inform.
