12.56 Aeroplane Aerodynamic Theory

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

The coefficient of lift (CLC_LCL​) 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 CLC_LCL​.

1. Effect of Flaps

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

Effect on CLC_LCL​:

• Increases CLC_LCL​ at any given AoA
• Increases maximum CLC_LCL​ (CLmaxC_{L_{max}}CLmax​​)
• Shifts the lift curve upward
• Increases drag, particularly at large flap settings