The winglets of an airplane are the fins, they are usually vertical, and are located at the tip of the wing. These make it possible to reduce the induced resistance. In other words, they serve to prevent the air flow from the soffit from mixing with that from the extrados due to the difference in pressure between them.
This generates wingtip eddies that increase drag and thus slow the aircraft. Also during takeoff and landing maneuvers, the important vortices that are generated at the tip of the planes, with speeds of up to 90 kilometers per hour, constitute a serious danger for lighter aircraft that could take off or land later.
In fact, in the flight plans (Flight Plan) aircraft are categorized according to their turbulent wake: Superheavy (super), reserved for aircraft such as the Airbus 380 or the Antonov 225; Heavy, for aircraft with a maximum take-off weight (MTOW) of 136,000 kg or more; Medium (medium), aircraft with an MTOW of less than 136,000 kg but more than 7000 kg, and finally Light (light), for aircraft weighing 7,000 kg or less.
All these classifications and their effects on the formation of turbulent contrails vary significantly depending on whether or not the winglets are incorporated into the aircraft structures. In the next section we explain its usefulness in more depth.
Usefulness of airplane winglets
An airplane is sustained thanks to the difference in pressure of the air that circulates through the lower part (intrados) with respect to the upper face (extrados) of the wing. But of course, at the end of the wing there is nothing that separates these mentioned sides, so when they come together they generate eddies that become an important source of aerodynamic resistance.
The use of winglets makes it possible to considerably reduce the size of the vortices, since it induces a more gradual contact of both air masses. Therefore, the winglets reduce aerodynamic drag and thus allow lower fuel consumption. As you know, the search for fuel savings is one of the priority objectives of companies such as Airbus or Boeing since it constitutes a key element in optimizing the performance and efficiency of modern aircraft.
You can read the article on the fuels of the future that are already being investigated.
Types of winglets
Es el diseño más básico y, al que cualquier persona si se habla de winglets reconocerá.
El winglet fence es una variante introducida por Airbus en los modelos de la familia A320, y también –con modificaciones- en el A380. Tal y como su nombre indica, es una barrera de punta de ala. Sobresale tanto por arriba como por abajo, para propiciar que el flujo de aire mantenga una trayectoria paralela a la del avance del avión, y evitar que el aire a mayor presión de debajo del ala forme torbellinos con el flujo a menor presión de la parte superior.
The Blended winglet is the optimized solution found by Boeing. They are larger and more striking, since they are characterized by being like a “mini vertical wall”, that is, it is like a vertical extension of the wing.
Airbus baptized its version very similar to blended ones. These reduce consumption by 3.5%, so the company began to implement them in the A320 neo. They are named for their resemblance to a shark fin.
Split Scimitar winglet
In 2016, Boeing engineers further sharpened the upper profile and added a new fin on the underside of the wing. This new design improves the efficiency of the aircraft by 2%. It is the model that incorporates the B737 Max.
Ultimately, Boing decided to reinvent the wing completely. The result was a very long, sharp wingtip with a certain angle of twist.
But there are several problems with this new model. The first is that they are not as effective during ascent and descent, but for when the plane reaches cruising speed, making it more useful for long-haul aircraft. It is the design that we can see in the B787 Dreamliner.
The second problem is the length of the wings. At airports, space for each aircraft is limited, so Boeing engineers converted foldable winglets on the ground to reduce size. In the case of the B777X, the folding of the tips of the planes reduces the wingspan of the aircraft by 3.3 meters.