Which four factors primarily determine lift magnitude for a fixed-wing aircraft?

• A. Wing area, air density, velocity, and angle of attack
• B. Wing span, engine power, altitude, temperature
• C. Aircraft color, surface roughness, humidity, ground speed
• D. Lift coefficient, drag coefficient, weight, thrust

Answer: (A)

Lift is determined by the equation L = 1/2 ρ V^2 S CL, so the four factors that set its magnitude are the wing area (S), the air density (ρ), the velocity through the air (V), and the lift coefficient (CL). The lift coefficient is how effectively the wing converts inflow into lift, and in normal flight CL is governed mainly by angle of attack: increasing the angle strengthens the lift up to the point of stall. So increasing wing area adds more surface to generate lift, higher air density or faster speed increases the dynamic pressure acting on that surface, and a larger angle of attack raises CL and hence lift.

Why the other options don’t fit: engine power doesn’t directly determine the instantaneous lift, and while altitude or temperature affect air density, they aren’t four direct determinants of lift themselves. Choices including surface roughness, color, humidity, or ground speed likewise don’t set the lift magnitude in the same direct way. The set that captures the essential factors is wing area, air density, velocity, and angle of attack (through CL).