How does wing aspect ratio affect efficiency?

How does wing aspect ratio affect efficiency?

• A. Higher aspect ratio reduces induced drag and typically improve lift-to-drag ratio, especially at lower speeds.
• B. Higher aspect ratio increases induced drag.
• C. Higher aspect ratio has no effect on efficiency.
• D. Higher aspect ratio reduces wing stiffness.

Answer: (D)

The main idea is that wing aspect ratio changes aerodynamic efficiency mainly through induced drag. When a wing has a higher aspect ratio—it's longer and narrower for the same lift—the wingtip vortices created to produce lift are spread over a larger span. This weakens the strength of those vortices per unit lift, reducing induced drag. As a result, the lift-to-drag ratio improves, particularly at lower speeds where induced drag is the dominant component. This explains why a higher aspect ratio is beneficial for efficiency: you get less energy wasted in vortices while still generating the needed lift. At higher speeds, other forms of drag become more important, so the benefit can level off, but the basic relationship remains that increasing aspect ratio lowers induced drag and improves overall efficiency. The other statements don’t fit because increasing aspect ratio doesn’t inherently raise induced drag; it doesn’t have no effect on efficiency, and stiffness isn’t the primary or reliable consequence of aspect ratio. A high aspect ratio wing can be designed to be stiff or flexible as needed, but stiffness isn’t the reason it affects efficiency.

The main idea is that wing aspect ratio changes aerodynamic efficiency mainly through induced drag. When a wing has a higher aspect ratio—it's longer and narrower for the same lift—the wingtip vortices created to produce lift are spread over a larger span. This weakens the strength of those vortices per unit lift, reducing induced drag. As a result, the lift-to-drag ratio improves, particularly at lower speeds where induced drag is the dominant component.

This explains why a higher aspect ratio is beneficial for efficiency: you get less energy wasted in vortices while still generating the needed lift. At higher speeds, other forms of drag become more important, so the benefit can level off, but the basic relationship remains that increasing aspect ratio lowers induced drag and improves overall efficiency.

The other statements don’t fit because increasing aspect ratio doesn’t inherently raise induced drag; it doesn’t have no effect on efficiency, and stiffness isn’t the primary or reliable consequence of aspect ratio. A high aspect ratio wing can be designed to be stiff or flexible as needed, but stiffness isn’t the reason it affects efficiency.