Nerves in the body's skin, muscles, and joints constantly send signals to the brain, which signals the body's relation to gravity
These tactile signals tell the pilot his or her current position
Acceleration will be felt as the pilot is pushed back into the seat
Often termed "flying by the seat of your pants"
Forces created in turns can lead to false sensations of the true direction of gravity, and may give the pilot a false sense of which way is up
Uncoordinated turns, especially climbing turns, can cause misleading signals to be sent to the brain
Skids and slips give the sensation of banking or tilting
Turbulence can create motions that confuse the brain as well
Pilots need to be aware that fatigue or illness can exacerbate these sensations and ultimately lead to subtle incapacitation
Postural Considerations:
The postural system sends signals from the skin, joints, and muscles to the brain that are interpreted in relation to the Earth's gravitational pull
These signals determine posture
Inputs from each movement update the body's position to the brain on a constant basis
Again, "seat of the pants" flying is largely dependent upon these signals
Used in conjunction with visual and vestibular clues, these sensations can be fairly reliable
However, because of the forces acting upon the body in certain flight situations, many false sensations can occur due to acceleration forces overpowering gravity
These situations include uncoordinated turns, climbing turns, and turbulence
Figure 1: Instrument Flying Handbook, Sensations From Centrifugal Force
