Definition
The body's system of nerve endings in the skin, joints, and muscles that sense pressure, stretch, and position, and feed that information to the brain to help judge orientation, balance, and movement. In flight, it is one of three orientation systems pilots rely on, alongside vision and the vestibular (inner ear) system, and it is easily fooled because it cannot distinguish between the pull of gravity and the pull of acceleration.
Plain English
The 'seat of the pants' sense -- the feel you get from your skin, muscles, and joints that tells your brain how your body is positioned and which way is down. It works fine on the ground but can mislead you in flight because the forces from turning, climbing, or accelerating feel similar to gravity.
Context Anchor
Seen in instrument flying when learning why body feelings, sometimes called “seat-of-the-pants” cues, cannot be trusted by themselves.
Derivation
From Latin 'postura,' meaning position or posture. The term refers to the body's sense of its own posture and position in space.
Why Pilots Care
In instrument conditions the postural system supplies misleading signals that can lead to spatial disorientation and loss of control if the pilot does not rely on flight instruments instead.
Grounding Statement
Sit in a car with your eyes closed as it accelerates from a stop -- you feel pressed back into the seat and it feels like you're tilted backward, even though the car is level. That same illusion happens to pilots, and the postural system is what produces it.
Intuition Check
Postural does not mean only sitting up straight or having good posture. Here it means the body-sense that reports pressure, lean, and movement.
Example Sentence 1
During the night takeoff, the pilot felt the airplane was pitching up steeply, but recognized this as a false signal from the postural system and trusted the attitude indicator instead.
Example Sentence 2
Pilots learn to disregard postural system cues and trust the instruments when visual references disappear.