Two airplanes have wings of equal wing area but different aspect ratios: Airplane A has a long, narrow wing (high aspect ratio), and Airplane B has a short, wide wing (low aspect ratio). At the same airspeed and angle of attack, which statement is correct regarding induced drag?
- AAirplane A produces less induced drag because parasite drag increases proportionally with span
- BAirplane A produces more induced drag because wingtip vortices are stronger with longer wings
- CAirplane B produces more induced drag because its shorter span concentrates wingtip vortex effects over a larger portion of the wing
- DBoth airplanes produce identical induced drag since wing area is the same
Show answer & explanationAnswer & explanation
Correct answer: C. Airplane B produces more induced drag because its shorter span concentrates wingtip vortex effects over a larger portion of the wing
Aspect ratio (span squared divided by wing area) affects induced drag: a high-aspect-ratio wing (long and narrow) spreads the wingtip vortex influence over a smaller percentage of the span, producing less induced drag, while a low-aspect-ratio wing (short and wide) has the vortex effects influencing a greater proportion of the wing, resulting in more induced drag.
Why the other options are wrong
- A. Parasite drag is unrelated to aspect ratio in this way; this option conflates parasite and induced drag.
- B. This reverses the correct relationship; higher aspect ratio wings have proportionally less induced drag.
- D. Wing area alone does not determine induced drag; span and aspect ratio are critical factors.
Aspect Ratio and Induced Drag
Aspect ratio is the ratio of wingspan squared to wing area; higher aspect ratio wings (long, narrow) produce less induced drag than lower aspect ratio wings (short, wide) of the same area.
- Aspect ratio = span² / wing area
- High aspect ratio = long, narrow wing (e.g., gliders)
- Induced drag decreases as aspect ratio increases
- Low aspect ratio wings have proportionally greater wingtip vortex influence
Memory trick: 'Long and lean cuts the vortex scene' — high AR = less induced drag