Lift: what is it?

• A. A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind
• B. Thrust
• C. Drag
• D. Weight

Answer: (A)

Lift is the force component that acts perpendicular to the oncoming air (the relative wind) on an airfoil. It arises because the wing’s shape and angle of attack create pressure differences between the upper and lower surfaces, pushing the wing upward as air is deflected downward. The total aerodynamic force on the wing can be split into lift (perpendicular to the relative wind) and drag (parallel to the relative wind). Thrust is the forward propulsion force, and weight is gravity pulling downward, so lift is the part that stands apart by its direction and its role in supporting the aircraft’s weight. The size of lift depends on air density, velocity, wing area, and the lift coefficient.