Plain English Meaning

When you can't see outside, your body can fool you. The same forces you feel when sitting upright on the ground can feel identical to the forces felt in a banked turn or a climb, so what your body 'tells you' about the aircraft's position is often wrong.

Full Definition

The effect that a pilot's body position and physical sensations have on the perception of aircraft attitude and motion, particularly when outside visual references are lost. Without a visible horizon, the brain may interpret the pull of gravity and the forces of acceleration, turning, or climbing as if they indicate which way is up, leading to false impressions of the aircraft's actual attitude.

Context Anchor

Seen in instrument flying discussions about and why pilots must trust the instead of body sensations.