Explain why a wing with high aspect ratio is more efficient than a low aspect ratio wing in cruise.

Explain why a wing with high aspect ratio is more efficient than a low aspect ratio wing in cruise.

• A. High aspect ratio reduces induced drag by producing a more elliptic lift distribution, increasing L/D; practical constraints limit AR.
• B. High aspect ratio increases induced drag.
• C. High AR reduces structural weight, increasing efficiency.
• D. AR has no effect on cruise efficiency.

Answer: (A)

Understanding induced drag is key here: the drag that arises from lifting the wing. The lift distribution across a wing that’s close to elliptic minimizes the wing wake and the downwash behind the wing, which in turn reduces induced drag. A high aspect ratio wing, with a longer span relative to its area, supports a lift distribution that is closer to this ideal elliptic shape. That means for the same total lift, the wing produces less induced drag, so the overall lift-to-drag ratio improves and cruise efficiency goes up. Of course, you don’t design in a vacuum. Making the wing very long introduces practical trade-offs—structural weight and complexity rise, bending moments increase, and there are other performance and integration considerations. So while a higher aspect ratio lowers induced drag and boosts efficiency in cruise, real aircraft balance these benefits against the added constraints. The idea that aspect ratio would increase induced drag or has no effect isn’t correct, and higher AR doesn’t automatically reduce structural weight.

Understanding induced drag is key here: the drag that arises from lifting the wing. The lift distribution across a wing that’s close to elliptic minimizes the wing wake and the downwash behind the wing, which in turn reduces induced drag. A high aspect ratio wing, with a longer span relative to its area, supports a lift distribution that is closer to this ideal elliptic shape. That means for the same total lift, the wing produces less induced drag, so the overall lift-to-drag ratio improves and cruise efficiency goes up.

Of course, you don’t design in a vacuum. Making the wing very long introduces practical trade-offs—structural weight and complexity rise, bending moments increase, and there are other performance and integration considerations. So while a higher aspect ratio lowers induced drag and boosts efficiency in cruise, real aircraft balance these benefits against the added constraints. The idea that aspect ratio would increase induced drag or has no effect isn’t correct, and higher AR doesn’t automatically reduce structural weight.