What is the most common form of spatial disorientation?

The Leans is recognized as the most common form of spatial disorientation experienced by pilots. This phenomenon occurs when a pilot is subjected to a gradual and sustained banking of the aircraft. If the pilot makes a slight recovery and erroneously perceives that the airplane is level, they may experience a misleading sensation. This leads to a misjudgment of the aircraft's actual orientation. As they continue to believe the aircraft is upright, any abnormal visual cues might not be registered, making them susceptible to continued misperception and further disorientation.

Understanding the Leans highlights the importance of trust in instruments during flight, especially when visual references are compromised. It underscores why pilots are trained extensively in instrument flying, to maintain spatial awareness regardless of the aircraft's actual position in relation to the horizon. This contextual awareness is crucial, especially in conditions of low visibility or night flying, where the risk of becoming disoriented is significantly heightened.