12.56 Aeroplane Aerodynamic Theory

12.56.2 Show how CL varies with use of flaps and control surfaces

The coefficient of lift (CL) depends primarily on angle of attack (AoA) and wing configuration. The use of flaps and control surfaces alters the wing’s shape and AoA, thereby changing CL.

1. Effect of Flaps

Principle:
Flaps increase wing camber (curvature), which increases lift at a given AoA.

Effect on CL​:

• Increases CL​ at any given AoA
• Increases maximum CL (CLmax​​)
• Shifts the lift curve upward
• Increases drag, particularly at large flap settings