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- 5.Winglets and Sharklets – Wingtip Devices Explained!
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Most modern commercial aircraft have wings that are folded up at the tip today. These folded up ends are “winglets” (or, depending on the shape, sharklets, wingtips, etc.). Of course, these wingtip devices do not only look great. They also have a specific purpose. This article will elaborate a bit more on this topic. Buckle up and have fun!
Wake turbulences – Uneconomic and Dangerous!
In flight, an aircraft produces so-called wake turbulences behind it. These are pommel-like, counter-rotating air turbulences. On very wet days, you can watch them as narrow strips behind the wings. This phenomenon is especially interesting for planespotters like me, since those vortices can look amazing.
Depending on the weight of the aircraft, these wake vortices have different strengths. The higher the mass of the aircraft, the stronger the wake turbulence. Depending on the intensity of this wake, this can become quite dangerous for aircraft flying behind the plane producing the turbulence. This is especially the case, if these planes flying behind are smaller and lighter.
This fact necessitates a decent separating of the aircraft in approach and departure, which is a major factor in the maximum capacity of an airport, since this separating results in a constraint of the maximum movements an airport can handle per hour.
Let me give you a brief example. A Cessna Citation, that wants to land behind an A380, has to fly at least eight nautical miles behind the colossus, at a time interval of three minutes.
What are Winglets Good for?
But not only for other aircraft wake turbulence are unfavourable; turbulent air also has a negative effect on fuel consumption. Here, the winglets come into play, because they compensate for the air turbulence occurring at the wing edges and thus reduce the consumption of kerosene by about 3-5%. That also makes the residents near airports happy, since the lower “lift-induced drag” also leads to a lower thrust needed. The noise emissions from the aircraft decrease!
Another advantage is that these winglets also reduce vibrations on the wings. Wingtip Devices can be quite high depending on the design. The largest ones are found on the Boeing 767-300ER (3.45 meters). A modern form of the wingtip devices are the “raked Wingtips“, which are wings elegantly curved upwards, as it can be seen on the Boeing 787. This form was made possible by new construction materials and comes very close to the role model nature provides to us: A bird’s wing!
Winglets – A Brief History!
By the way, a certain Frederick W. Lanchester already had the idea for winglets in 1897. So even before the first motor-powered flight! He filed the corresponding patent. During the Second World War, some aircraft applied this idea. In 1970, in the wake of the oil crisis, NASA decided to continue to develop and advance the old patents. The first passenger aircraft with winglets (at that time as so-called “Wingtip Fences”) was the Airbus A310-300.
Winglets and Sharklets – There Are Also Downsides!
So, winglets reduce the lift–induced drag of the aircraft, and, consequently, fuel consumption decreases. This effect is always strong if the angle of attack of the aircraft is high, namely in phases of “slow-flight“. Among those phases are the landing, take-off and cruising phase. In those phases, the true airspeed, hence the speed of the aeroplane relative to the airmass in which it is flying is lower. That is why winglets are particularly efficient on routes with high shares of cruise flight.
Sadly, wingtip devices also have a disadvantage, because of course they also weigh something. And every kilogram that an aeroplane has to tow into the air costs fuel! In addition to that, not only the winglets increase in weight. The wing ends must be strengthened during retrofitting with wingtip devices. Moreover, they do also increase the aircraft’s wingspan. The flight behaviour changes, according to pilots, noticeable.
That is why it makes quite a difference whether you fly a conventional Airbus A320 or one with retrofitted sharklets. Due to the lower induced drag, the aircraft does not react so quickly to thrust reductions. Sharklets also act like an enlargement of the vertical stabilizer (the thing at the rear of the aircraft on which the Airline logo emblazoned). As a result, higher rudder deflections are needed for crosswind landings.
More Aviation Knowledge!
You want to learn more about the complex world of aviation and flying? Feel free to browse through my “Aviation 101” section. Also, you might want to read my article about the instrument landing system!
I do hope that you have enjoyed this article about winglets, sharklets and wingtip devices. More aviation know-how will come every week on pilotstories. In the meantime, feel free to subscribe my email newsletter and to follow me on Facebook and Instagram. My free aircraft wallpapers are available here!