SEAT-OF-THE-PANTS

Proprioceptors are components of the nervous system and are located under the skin (subcutaneous) in the neck and the major parts of the body, as well as muscle activity sensors. Proprioceptive sensory inputs give us a reference to posture and the relative position of our body in relation to our environment. A pilot relying on these inputs is sometimes referred to as flying by the “seat-of-the-pants”.

Under VMC, the proprioceptive (seat-of-the-pants) sense can be quite helpful. Without ever noticing, we use our proprioceptive sense in everyday life to finetune our movements. In VMC, this sense can give us valuable additional information that can help us finetune our motor actions. But proprioception can only be helpful in combination with vision.

• Under IMC, the pilot loses vital visual input and the seat-of-pants is no longer able to tell the cause of a sensed pressure and will not provide any valuable data. For instance, if the aircraft goes into a descent it will accelerate and this acceleration, via the otoliths, will inform the pilot that the aircraft is in a climb. The proprioceptors will also detect a climb. Therefore, this system becomes unreliable for lack of visual support and must not be used for spatial orientation. Pilots must rely on the aircraft instruments to avoid disorientation.