What is the critical angle of attack?

What is the critical angle of attack?

• A. The maximum bank angle before a turn stalls.
• B. The angle at which tail downforce counters nose-down moment.
• C. The angle where thrust equals drag.
• D. The angle of attack at which lift begins to rapidly decrease as flow separates.

Answer: (D)

The critical angle of attack is the angle where lift stops increasing with AoA and begins to fall off rapidly because the airflow can no longer stay attached to the wing and separates from the surface. As you push the wing toward stall, the boundary layer detaches, causing a sharp drop in lift and a large increase in drag. This is the condition planes must avoid or recover from, since lift is lost even if speed is still high. So the correct concept describes lift deteriorating due to flow separation at a certain angle, not related to bank limits, tail-down balancing moments, or thrust versus drag.

The critical angle of attack is the angle where lift stops increasing with AoA and begins to fall off rapidly because the airflow can no longer stay attached to the wing and separates from the surface. As you push the wing toward stall, the boundary layer detaches, causing a sharp drop in lift and a large increase in drag. This is the condition planes must avoid or recover from, since lift is lost even if speed is still high.

So the correct concept describes lift deteriorating due to flow separation at a certain angle, not related to bank limits, tail-down balancing moments, or thrust versus drag.