What is the "leans" illusion specifically related to?

The "leans" illusion occurs when a pilot experiences the sensation of rolling in the same direction as a turn, even when the aircraft is not actually turning. This illusion typically arises from the vestibular system's interpretation of changes in the orientation of the body relative to gravity.

When a pilot is in a steady turn, their inner ear can begin to adapt to this new orientation, leading to the incorrect perception of bank. If the aircraft then levels off, the pilot may still feel that the airplane is in a banked position towards the direction of the previous turn. This can lead to spatial disorientation, where the pilot may believe the aircraft is still in a turn, prompting potential overcorrection and further issues in flight management. Understanding this phenomenon is crucial for pilots to maintain situational awareness and avoid misjudgments during flight maneuvers.