Angle of Attack
Angle of attack (AoA) is the angle between the chord line of the wing and the relative airflow (relative wind). It is the most critical aerodynamic variable — it determines how much lift the wing is producing and how close the wing is to a stall. Angle of attack is completely independent of pitch attitude.
Lift and the Critical Angle of Attack
As angle of attack increases, the coefficient of lift (CL) increases — more lift is generated. This continues up to the critical angle of attack (typically 15–20° for most light aircraft), beyond which airflow over the upper surface separates and lift collapses. This is the stall. The stall always occurs at the same critical AoA regardless of airspeed, weight, or attitude.
The Common Confusion: AoA vs. Pitch Attitude
A stall is caused by exceeding the critical angle of attack — not by a particular airspeed or pitch attitude alone. In a steep turn, the stall speed increases because the load factor increases, but the critical AoA at which the stall occurs remains the same. An aircraft can stall nose-down if the AoA is high enough.
AoA and Load Factor
Any time load factor increases (steep turns, pull-outs, turbulence), the stall speed increases proportionally. The relationship: stall speed increases with the square root of the load factor. At 60° bank, load factor is 2g and stall speed increases by approximately 41%.
On the TC Written Exam
AoA is one of the most tested aerodynamic concepts. Key facts: stall always occurs at the same critical AoA; AoA ≠ pitch attitude; load factor increases stall speed but not critical AoA; AoA indicators directly measure proximity to stall.
Related Terms
See also: Angle of Attack Indicator, Angle of Incidence, Aerodynamic Coefficients, Load Factor.