From the appearance of the first aircraft to present days, the aviation industry has been in constant development to achieve, with each new model, better energy efficiency while increasing safety and reducing environmental impact.
The appearance of the so-called winglets, or wingtip devices, was a major revolution in modern aerodynamics. These elements, installed on aircraft wing tips and designed with an angular and ascending shape, represent a key innovation in aeronautical engineering.
Winglets have their origin in the aerodynamic studies of Richard T. Whitcomb, a NASA engineer who developed the idea of adding small fins at the tips of the wings to improve aerodynamic efficiency. His research focused on reducing induced resistance, a phenomenon that occurs when the air flow around the wings generates vortices at their ends, which causes a loss of energy and increases advancement resistance.
In 1976, the NASA tested wind tunnels in an aircraft model equipped with winglets, achieving the expected benefits in terms of fuel efficiency and reduced drag. This promising innovation was first implemented on commercial flights in the 1980s.
In 1991, the American company Aviation Partners Inc. (API) pioneered the commercial application of winglets, certifying the first system for the Boeing 737. Since then, winglet technology has spread to a wide variety of airplanes, from commercial to private and military.
The success of winglets has led many aircrafts manufacturers to incorporate this feature into the design of new models. Besides API, other companies, such as Blended Winglet and Sharklet, have developed and marketed winglet systems for various aircrafts.
The winglets’ function is to improve aerodynamic efficiency and reduce induced drag by minimizing vortex formation.
These devices work by optimizing the pressure distribution along the wings, thus reducing drag force which results in lower fuel consumption and greater autonomy for the aircraft. It is important to note that they not only offer benefits in terms of fuel efficiency, but also have a positive impact on the overall stability and plane performance as they help to control air flow, improve take-off and landing characteristics, and reduce the structural load on the wings. In addition, by decreasing resistance, these devices contribute to a smoother and more efficient flight.
Winglet design and implementation vary depending on each aircraft manufacturer and model. Some airplanes incorporate winglets from their design phase, while others may be equipped with them during modifications or upgrades.
Winglet is the “generic” name applied to wingtip devices. Specifically, it is how the most basic and simple design is called. However, there are different types, each of them designed to address specific needs in terms of aerodynamic efficiency and performance. Let’s see some of them:
These are the most conventional. They are installed vertically on the wingtips and their shape resembles a small fin that extends upwards. Vertical winglets are effective in reducing induced resistance and improving fuel efficiency.
Wingtip fences are a more discreet variant of winglets. It was introduced by Airbus into the A320 family and, as its name suggests, is a «barrier» tip of wing. It protrudes both above and below in order to prevent the air at higher pressure «escaping» from under the wing.
These winglets were the optimized solution that Boeing found to minimize induced resistance. With a smooth transition, as if they were a wing extension, blended winglets integrate more smoothly with the wing contour, which can improve aesthetics as well as minimize resistance. Much larger and more striking, they became known as the winglets of the Boeing 737-800 by their massive introduction into this model.
Boeing tried to design a wing in which the wing’s own tip shape deflected the air flow avoiding the formation of vortices. The result was a very long, sharp wing tip with a certain twist angle that works even better than conventional winglets.
However, there are two small problems. The first is that they are only more efficient than classic winglets during the cruise phase. In the ascent and descent, they are not so. Thus, Boeing uses them only in long-range aircrafts, as the Boeing 787, in which the cruise phase is the longest phase of the flight. On a Boeing 737, which performs much shorter journeys, it is not worth it.
The second problem is that for raked wingtips to have the optimal shape, the wingspan increases considerably. This may be a problem in some airports where the parking lots have a limited width. Therefore, raked wingtips were suitable for the B787, but in the new Boeing 777X would make a too long span which led Boeing to design raked foldable winglets deployable before takeoff.
In 2016, Boeing turned the blended winglets around, sharpening the top profile even further and adding a new fin at the bottom of the wing. It is named after its similarity to the scimitars (curved and sharp swords of the Middle East). Split scimitar winglets provide additional aerodynamic benefits over conventional ones and are a popular option to improve fuel efficiency as, in addition to having a much more aggressive design, they manage to enhance the efficiency of the plane by a not despicable 2%.
With the development of the A350, Airbus engineers had the opportunity to design the so-called “sharklets” together with the wing. The result was a thinner wing tip and a 3.5% consumption reduction.
The choice of winglet type depends on several factors, which includes aircraft design objectives, mission type and aesthetic considerations. Each type has its own advantages in terms of aerodynamic efficiency and contribution to the overall performance of the aircraft.
At the time, the appearance of Airbus sharklets generated some controversy, winglets vs sharklets, for its great similarity with the Boeing blended winglets whose inventors, the company Aviation Partners, claim that those are based on their idea so they demanded financial compensation from Airbus.
Since the term winglet was directly associated with the blended winglets of the Boeing 737-800, Airbus named its design “sharklets” after its shark fin shape.
The winglet concept has evolved over time, and its application has become a standard practice in the aviation industry. This technology is crucial to the industry’s efforts to improve efficiency, reduce emissions and make aviation more sustainable, as well as contributing to a smoother and more efficient flight.
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