Formula & Calculator
Wing Aspect Ratio
Ratio describing how long and slender a wing is relative to its area; strongly influences induced drag.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| AR | Aspect ratio | |
| b | Wingspan | m |
| S | Wing area | m2 |
What it means
Aspect ratio is a geometric parameter that significantly influences induced drag. High AR wings (e.g., gliders) have lower induced drag but higher structural weight. It is defined as the square of the span divided by the area. For a rectangular wing, AR = span/chord. The aspect ratio appears in the induced drag equation: C_Di = C_L²/(π e AR). Increasing AR improves aerodynamic efficiency, which is why high‑altitude long‑endurance aircraft have large spans. However, high AR can cause structural issues and require more complex wing designs. Understanding AR is essential for wing optimisation and trade‑off studies.
Worked example
Wing Aspect Ratio – Two Examples
Real‑World| Parameter | Value |
|---|---|
| b | 20 m |
| S | 30 m² |
| Parameter | Value |
|---|---|
| b | 12 m |
| S | 25 m² |
Common mistakes
- Aspect ratio AR: AR = b² / S – dimensionless.
- Wingspan b: In metres.
- Wing area S: In m².
- High AR: Indicates slender wing (e.g., gliders) – reduces induced drag.
- Geometric vs. effective: Effective AR may be reduced by winglets or endplates – use geometric for standard.
Applications
Wing aspect ratio, AR = b²/S, is the ratio of wingspan squared to wing area. High aspect ratio wings are long and slender, offering lower induced drag, while low aspect ratio wings are stubby and provide higher structural strength and roll rates. This parameter is a primary driver of aerodynamic efficiency and structural design. Engineers use AR to optimise wings for specific missions: gliders have high AR for endurance, while fighters have low AR for manoeuvrability. Aspect ratio also affects spanwise lift distribution, wingtip vortices, and wake turbulence. By selecting the appropriate AR, aerospace engineers balance aerodynamic performance, structural weight, and manufacturability to meet design requirements.
- Wing planform design for desired lift‑to‑drag ratio
- Trade‑off between induced drag and structural weight
- Design of gliders, UAVs, and high‑endurance aircraft
- Fighter aircraft wing design for agility
- Wake turbulence and airport spacing regulations