Airfoil anatomy
Airfoil: surface shaped to react to moving air. Wing cross-section is the classic example (PHAK ch.4).
| Term | Definition |
|---|---|
| Leading edge | Rounded front, faces forward in flight |
| Trailing edge | Narrow, tapered rear |
| Chord line | Straight line joining leading and trailing edge extremities |
| Camber | Curvature of upper or lower surface, measured from chord line. Maximum camber = greatest convexity from chord (TP 1102) |
| Mean camber line | Line from leading to trailing edge, equidistant from upper and lower surfaces at every point. Curves with airfoil shape |
| Angle of attack (AoA) | Acute angle between chord line and relative wind direction (TP 1102 ch.1) |
| Angle of incidence | Fixed angle between wing chord and aircraft longitudinal axis. Set by airframe (TP 1102 ch.1) |
| Relative wind | Direction airflow meets aircraft. Parallel to and opposite actual flight path; unrelated to aircraft attitude (PHAK glossary, "Relative wind") |
- Typical (non-symmetrical) airfoil: upper surface camber more pronounced (TP 1102 ch.1); lower surface usually nearly flat.
- Incidence is not AoA: AoA varies with relative airflow (TP 1102 ch.1).
Trap: chord line and mean camber line both run leading edge to trailing edge but differ: chord line straight, mean camber line curves.
References
- PHAK ch.4 Principles of Flight
- TP 1102 ch.1 Boundary Layer