Which statement best describes stall margin as it relates to weight, configuration, load factor, and density?

• A. Stall margin depends only on weight.
• B. Heavier weight increases stall speed and reduces margin; weight is the sole factor.
• C. Stall margin depends on weight, configuration (flaps, gear), load factor, and density; heavier weight increases stall speed and generally reduces margin, while certain configurations can lower stall speed but alter margin.
• D. Flap settings have no impact on stall speed.

Answer: (C)

Stall margin is the cushion between your current airspeed and the speed at which the wing stalls, and it changes with weight, configuration, load factor, and density. Heavier weight means the wing must produce more lift to support the airplane, so the stall speed rises. At the same flight speed, you’re closer to the stall, so the margin shrinks. The aircraft’s configuration, such as flap and gear settings, alters how much lift the wing can generate at a given speed. Deploying flaps generally increases lift and lowers stall speed, which can increase margin at a given speed, but it also changes the margin calculation because the stall speed itself has changed. Increased load factor, such as when turning, raises the required lift and thus raises stall speed, reducing margin. Air density also plays a role: in thinner air (higher altitude), you need higher airspeed to generate the same lift, so stall speed increases and margin decreases. Because all these factors interact to determine stall speed and the airplane’s operating speed, the best description is that stall margin depends on weight, configuration, load factor, and density; heavier weight increases stall speed and generally reduces margin, while certain configurations can lower stall speed but alter the margin.