MAC262 – ACFT Limits And Speeds Practice Test

Stall speed is the speed at which the wing can just generate enough lift to balance the aircraft’s weight in level flight, with the lift coefficient at its maximum. Lift is L = 0.5 ρ V^2 S CL, and at stall CL equals CLmax, while in level flight L must equal W. Solving for V gives Vstall = sqrt((2W) / (ρ S CLmax)). This shows that as weight W increases, Vstall increases proportionally to the square root of weight. The intuition is simple: carrying more weight requires more lift, and since CLmax is fixed for a given configuration, you must fly faster to develop the needed lift. Lighter weight lowers the stall speed, while heavier weight raises it. The effect happens for any configuration (flaps, gear, etc.), though changing configuration alters CLmax and thus the actual stall speed.