How does increasing gross weight affect stall speed and takeoff distance, assuming other factors remain constant?

• A. Stall speed increases with the square root of weight; takeoff distance increases because more speed and lift are required.
• B. Stall speed decreases as weight increases; takeoff distance increases.
• C. Stall speed is proportional to weight; takeoff distance remains constant.
• D. Stall speed is independent of weight; takeoff distance decreases with weight.

Answer: (A)

Increasing gross weight raises both stall speed and takeoff distance, under constant factors like wing area, air density, and maximum lift coefficient.

At stall, lift equals weight. With a fixed wing, the required lift depends on weight, so the speed needed to generate that lift follows the relation V_s ∝ sqrt(W). This means stall speed increases with the square root of weight: doubling the weight raises stall speed by about 1.414 times.

For takeoff, you must accelerate to a higher takeoff speed to reach enough lift to become airborne. Heavier weight also adds inertia and increases the thrust required to overcome drag, so the airplane accelerates more slowly to that higher speed. The result is a longer ground roll and thus a longer takeoff distance.

So, heavier weight → higher stall speed (by the square root of weight) and longer takeoff distance.