Page 123 - Aeronautical Engineer Data Book

Basic aerodynamics 99
Characteristics for an asymmetrical ‘infinite-span 2D airfoil’
Stall
point

1.5 75
L/D
C L and 10 C D 1.0 C L 50

0.5 25 L/D
10 C D
0
–5˚ 0 5˚ 10˚ 15˚ 20˚
α
–0.5 –25
C L = 0 at the no-lift angle (–α)

Characteristic curves of a practical wing
2.0 0.20

1.6 0.16
C L
1.2 0.12
C D
C L
0.8 0.08
0.4 0.04
C D
0 0

–0.4 –0.04
C M 1/4
–0.08
C M 1/4
–0.12

–8˚ –4˚ 0˚ 4˚ 8˚ 12˚ 16˚ 20˚
α

Fig. 6.3 Airfoil coefficients