During lift, how does the pressure on the lower surface compare to the pressure on the upper surface?

• A. Lesser
• B. Greater
• C. Equal
• D. Variable

Answer: (B)

When the wing generates lift, the pressure on the lower surface is greater than the pressure on the upper surface. The wing’s cambered shape and angle of attack deflect air downward, causing the air beneath the wing to be pushed and slowed less or even accelerated, which raises its pressure relative to the air above. Over the upper surface, the flow speeds up and pressure drops. This pressure difference across the wing’s surfaces produces a net upward force – lift. The exact pressures vary with speed and angle of attack, but the key point is that the lower surface carries higher pressure than the upper surface during lift.