Angle of Attack Sensor

An angle of attack sensor is a flight instrument that measures the angle between the wing chord and the relative wind, providing the critical data that flight control systems use to determine whether an aircraft is approaching a stall. These sensors are not merely passive measuring devices; they are the sensory organs of the aircraft's stability analysis loop, translating the aerodynamic state of the wing into electrical signals that inform control decisions.

There are two primary types: vane sensors, which physically align with the airflow like a weather vane, and differential pressure sensors (often called smart probes), which infer angle of attack from pressure differentials across the probe surface. Neither type is immune to failure — vanes can ice over or jam; pressure ports can clog — which is why safety-critical aircraft design demands redundant sensors with cross-validation logic. The reliance on a single angle of attack sensor in the Boeing 737 MAX MCAS system was a violation of this principle, with catastrophic consequences.

The angle of attack sensor exemplifies a broader systems problem: the gap between what a sensor measures and what a control system assumes it knows. Every sensor is a model — a simplified, instrumented proxy for a physical state — and every model has regimes where it fails. Treating sensor output as ground truth rather than as one input among many in a fault-tolerant estimation framework is not engineering efficiency; it is epistemic overreach.