What are long, thin wings for? A talk about aspect ratio
Have you ever seen a glider and wondered, "Why are they so long?" There is a good reason for that. The key to understanding it is hidden in the term "Aspect Ratio (AR)." In this article, I will explain the concept of aspect ratio as clearly as possible.
■ What is aspect ratio? A number representing the slenderness of a wing.
Have you ever looked at an airplane's wings and thought, "They're long and thin," or "They're short and sturdy"? The metric that quantifies this is the "Aspect Ratio (Aspect Ratio)." Aspect ratio is defined as wingspan squared divided by wing area, and simply put, it is a number that indicates the "
slenderness of a wing".
Even with the same wing area, thin, long wings have a high aspect ratio, while short, thick wings have a low aspect ratio. Interestingly, this aspect ratio is also the key to describing an airplane's "character and mission".
■ Why do passenger planes have long, thin wings? A design for flying long distances
For example, when you look at a Boeing 787, its beautiful, long, thin main wings catch the eye. In fact, these wings have an aspect ratio of 11 (the B767 is about 8, and the B777 is about 9). The reason they are so long is for fuel efficiency. Wings with a high aspect ratio have the effect of suppressing "induced drag (resistance caused by wingtip vortices, etc.)" that occurs when generating lift. This reduces air resistance, allowing the plane to fly long distances with less fuel. In short, it means better fuel economy and cost-effectiveness. The fact that modern passenger planes have "bird-like wings" is the result of pursuing efficiency. However, there is a downside: making them too long increases the need for structural reinforcement and makes maneuvering at airports more restrictive.
■ Why are fighter jet wings short and sturdy? Prioritizing agility and structural strength
On the other hand, if you look at a fighter jet like the F-22 Raptor, the wings are compact and the aspect ratio is low (averaging about 2.5 to 3). Why is that?
That is because fighter jets require high-speed maneuvering and sharp turns. Short, thick wings are structurally strong and can better withstand the high G-forces (gravitational acceleration) placed on the airframe. Also, in supersonic flight, long wings actually become a source of drag, so shorter wings are more suitable. In other words,
"combat aircraft" prioritize responsiveness and strength over aerodynamics.
■ Why are glider wings so long? The wisdom of gliding without power
Gliders do not have engines and glide through the air using only altitude and updrafts. That is precisely why, to continue flying efficiently, they must minimize air resistance and maximize lift. In aviation terms, this is called the
lift-to-drag ratio (L/D ratio), and when the aspect ratio is high, induced drag (mainly resistance due to wingtip vortices) decreases, the L/D ratio improves, and they can continue flying for a long time even in weak air currents. For example, gliders like the "
ASW-27" or the "Discus-2" have a wingspan of over 15 meters and an aspect ratio reaching over 20. Long wings are the wisdom for "flying far".
■ Why do high-altitude aircraft have long, thin wings? To fly in a world of thin air
So, what about airplanes that fly at high altitudes? There is actually another type of airplane that has wings similar to a glider. These are the
U-2 reconnaissance plane or the Focke-Wulf Ta152H which are high-altitude aircraft. At altitudes exceeding 10,000 meters, the air is extremely thin, making it difficult to generate lift. This is where long, thin wings with a high aspect ratio come in. For example, the U-2 has a wingspan of over 30 meters and an aspect ratio of 24, giving it a shape like a "flying glider."
For the same reason, the Ta152H of the German Air Force, developed at the end of World War II, was also equipped with long wings. "To fly in the high sky, you need long wings." This is a point common to design philosophies of every era.
■ The shape of the sky tells the purpose of that airplane
Looking at it this way, we can see that the simple number known as aspect ratio is packed with an airplane's "purpose" and "philosophy."
Gliders: To fly far without power, the aspect ratio is made as high as possible
High-altitude aircraft: To gain lift in thin air, they also have a high aspect ratio
Passenger planes: High aspect ratio to improve fuel efficiency and achieve long-distance flight
Fighter jets: Prioritizing maneuverability and strength, they intentionally keep the aspect ratio low
And this is also common in birds. The wings of an albatross that migrates long distances are long and slender, while the wings of an eagle that makes sharp turns in high mountains are short and wide. It is interesting that both birds and airplanes end up with similar directions in evolution and design. Both airplanes and birds have shapes tailored to their respective ways of life on the common stage of the sky. It might be interesting to look at airplanes and birds flying in the sky with this bit of trivia next time (^^).
