During approach, which parameter is most critical to prevent stalls?

During approach, which parameter is most critical to prevent stalls?

• A. Airspeed
• B. Thrust
• C. Angle of Attack
• D. Sink rate

Answer: (C)

Angle of attack determines whether the wing stays in smooth, attached airflow or loses lift and stalls. A stall happens when the wing’s angle relative to the oncoming air reaches its critical value, causing boundary layer separation and a sudden drop in lift. During approach, you’re close to the stall boundary, so keeping the angle of attack below that critical value is the direct way to prevent a stall. Airspeed does influence stall margin because more speed generally means more lift for a given angle of attack, but it’s not the parameter that tells you you’re about to stall. You can have high thrust or high airspeed and still stall if you pitch up too much and exceed the critical angle. Conversely, you can maintain a safe angle of attack even as your speed changes. Sink rate relates to descent rate, not the lift/flow condition on the wing, so it’s not the primary indicator of impending stall. So, controlling how high the wing is climbing into the airflow—the angle of attack—is the most critical factor to prevent stalls on approach.

Angle of attack determines whether the wing stays in smooth, attached airflow or loses lift and stalls. A stall happens when the wing’s angle relative to the oncoming air reaches its critical value, causing boundary layer separation and a sudden drop in lift. During approach, you’re close to the stall boundary, so keeping the angle of attack below that critical value is the direct way to prevent a stall.

Airspeed does influence stall margin because more speed generally means more lift for a given angle of attack, but it’s not the parameter that tells you you’re about to stall. You can have high thrust or high airspeed and still stall if you pitch up too much and exceed the critical angle. Conversely, you can maintain a safe angle of attack even as your speed changes. Sink rate relates to descent rate, not the lift/flow condition on the wing, so it’s not the primary indicator of impending stall.

So, controlling how high the wing is climbing into the airflow—the angle of attack—is the most critical factor to prevent stalls on approach.