An aircraft airfoil is designed to produce lift resulting from a difference in the air pressure:

An aircraft airfoil is designed to produce lift resulting from a difference in the air pressure:

• A. Lower pressure below and higher above
• B. Higher pressure above and lower below
• C. Higher pressure below and lower above
• D. Equal pressure on both surfaces

Answer: (C)

Lift comes from a pressure difference between the wing’s surfaces. The airfoil’s shape and angle of attack make air flow faster over the top surface, lowering the pressure there, while the air underneath is at relatively higher pressure. That higher pressure beneath pushes the wing upward, and the lower pressure above provides less downward pull. The result is a net upward force. So the wing is designed to have higher pressure below and lower pressure above. If the top were higher than the bottom, or if pressures were equal, there would be less or no upward lift.

Lift comes from a pressure difference between the wing’s surfaces. The airfoil’s shape and angle of attack make air flow faster over the top surface, lowering the pressure there, while the air underneath is at relatively higher pressure. That higher pressure beneath pushes the wing upward, and the lower pressure above provides less downward pull. The result is a net upward force. So the wing is designed to have higher pressure below and lower pressure above. If the top were higher than the bottom, or if pressures were equal, there would be less or no upward lift.