The angle of attack indicator's operation is based on differential pressure measurement at a point where the airstream flows in a direction

The angle of attack indicator's operation is based on differential pressure measurement at a point where the airstream flows in a direction

• A. Parallel to the travel of the aircraft
• B. At rest in a stall condition
• C. Perpendicular to the travel of the aircraft
• D. Not parallel to the travel of the aircraft

Answer: (D)

An angle-of-attack indicator works by sensing how the airspeed component that meets the sensing port changes as the relative wind direction shifts with angle of attack. The pressure difference it uses comes from airflow hitting a port in which the flow is not aligned with the aircraft’s motion. If the air were flowing parallel to the flight path, there would be little or no change in that pressure difference with small changes in angle, so the indicator wouldn’t reflect the angle of attack accurately. Therefore the measurement point must be where the airstream flows in a direction not parallel to the travel of the aircraft. Contexts like “at rest in stall” describe conditions, not how the sensor operates, and choosing a direction that is exactly perpendicular to travel would still be an example of not-parallel flow, but the essential principle is simply that the flow direction at the sensing point is not parallel to the aircraft’s path.

An angle-of-attack indicator works by sensing how the airspeed component that meets the sensing port changes as the relative wind direction shifts with angle of attack. The pressure difference it uses comes from airflow hitting a port in which the flow is not aligned with the aircraft’s motion. If the air were flowing parallel to the flight path, there would be little or no change in that pressure difference with small changes in angle, so the indicator wouldn’t reflect the angle of attack accurately. Therefore the measurement point must be where the airstream flows in a direction not parallel to the travel of the aircraft.

Contexts like “at rest in stall” describe conditions, not how the sensor operates, and choosing a direction that is exactly perpendicular to travel would still be an example of not-parallel flow, but the essential principle is simply that the flow direction at the sensing point is not parallel to the aircraft’s path.