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How Does Aspect Ratio Affect Your Wing?

ErikBrouwer

Some wings are short and stubby, while others are long and skinny. What's up with the difference? It's more than just looks, and we'll explain why.

What Is Aspect Ratio?

First off, what is aspect ratio? It's the ratio of a wing's length to its chord. So for example, a wing that's long and skinny has a high aspect ratio, and a wing that's short and stubby has a low aspect ratio.

Advantages Of High Aspect Ratio Wings

High aspect ratio wings have one major advantage: because the wingtip has less area, there is less vortex induced downwash, which means a lot less induced drag.

Induced drag is most significant at low speeds and high altitudes (anywhere you have a high AOA), and since high aspect ratio wings have less of it, they perform very well in takeoff, landing, climb and cruise. So why don't all wings have a high aspect ratio? There are several reasons:

Air Loads

One of the most significant reasons is a structural one. The longer your wing is, the stronger it needs to be. That's because the air air load is placed across the entire span, which creates more of a bending moment.

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Think of it like a tape measure. When you pull the tape out a foot, it's pretty strong and stable, and it doesn't bend. But when you extend the tape out 8 feet, it starts to bend downward. Eventually, the tape collapses when it's pulled out far enough.

The same is true for a wing. The longer it is, the more it tends to bend. To overcome the bending, you need a stronger wing, which means you need more material. And when you add more material to the wing, it becomes heavier, which in turn means you'll produce more induced drag in flight. Eventually, the structural needs of a high aspect ratio design outweigh the benefits of the design.

Maneuverability

Another major factor of aspect ratio is maneuverability. Simply put, the longer your wing is, the less maneuverable it is. That's because longer wings have a higher moment of inertia. So a longer wing generally has less roll rate, and a shorter wing has more roll rate.

USAF

This is similar to a figure skater when they start doing those insanely fast spins. They typically start with their arms out, and when they pull their arms in, they reduced their moment of inertia, and they spin much faster.

Ice Skating Fastest Spin

Practical Design

The last major factor comes down to practical design. High aspect ratio wings have a few disadvantages. First, they aren't as thick, which means they don't have room for retractible landing gear.

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Second, they can't hold as much fuel for the same reason: less space.

James Willamor

And third, if large aircraft had extremely high aspect ratio wings, they would be nearly impossible to maneuver around airports. Their wings would hang over taxiways and runways, and you couldn't park them anywhere near each other.

Putting It All Together

High aspect ratio wings have a major advantage of creating less induced drag, but when it comes to wing design, that's only part of the story. Wing strength, maneuverability, and design practicality all play a part in the shape of your wing.

Colin Cutler

Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at colin@boldmethod.com.

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