The Stall

Definition

A stall is a loss of lift caused by the separation of airflow from the upper surface of the wing when the Critical Angle of Attack ($C_{L_{max}}$ angle) is exceeded.

• Fundamental Rule: A wing can stall at any airspeed, at any attitude, and at any power setting. It is purely a function of Angle of Attack.

Symptoms of Approaching Stall

1. Low Airspeed: Usually.
2. High Nose Attitude: Often, but not always (e.g., deep stall).
3. Sloppy Controls: Due to low airflow speed.
4. Buffet: Turbulent airflow hitting the tailplane.
5. Stall Warning:
   • Light Aircraft: Reed horn (suction).
   • Large Aircraft: Stick Shaker (artificial). Activates at approx 1.05-1.10 $V_{stall}$.

Stall Characteristics

• Root Stall First: Desirable. Ailerons (at tip) remain effective. Achieved by Washout (Twist).
• Tip Stall First: Dangerous. Loss of roll control. Pitch up tendency (due to CP moving forward on swept wings). Used on swept wing jets.

Recovery Procedure

1. Unload: Push the nose DOWN (reduce Angle of Attack). This is the PRIMARY action.
2. Power: Apply Max Power (TO/GA) to minimize altitude loss.
3. Roll: Wings Level.
4. Climb: Recover from dive.