AEROMEDICAL
When Pigs Fly
Cdr. Pete Wechgelaer MD, MPH
ave you ever felt that you’re rolling backward while stopped at a traffic light? That is spatial disorientation (SD). You weren’t moving, but you slammed on the brakes because it felt like you were. How does this happen? SD is a failure to correctly sense a position, motion or attitude of the aircraft or oneself within the fixed coordinate system provided by the earth and the gravitational vertical. It’s your ability to tell which way is up. Sounds simple enough, so why do we frequently get it wrong? It might have something to do with the fact we were not born with wings. Flying applies all kinds of novel inputs into your brain-housing group, and what you perceive is not always what’s really happening. 14
Let’s go back to the traffic-light experience. No motion was involved, so we can’t blame those tricky semicircular canals. It was your peripheral vision that caught a glimpse of movement and alerted your brain to that movement, and it felt like you were moving. The emphasis is on “felt like” because, even though your eyes only saw, you felt motion. Your eyes and brain misinterpreted what was happening, so what you felt wasn’t really what was happening. Consider what happens during every motion-based simulator flight. What you feel is not what actually is happening. The illusion is called vection, where the movement of something else, even an image, makes you feel like you are moving. Some people are more susceptible to it than others. Just looking at movement makes you feel like you are moving. It’s easy to get fooled, and we haven’t even discussed moving about and accelerating in three dimensions. Why is this information important? The Naval Safety Center has identified SD and fatigue as the top two aeromedical-causal factors of mishaps. I plotted the trend for SD mishaps and consistently found a horizontal line, meaning there is no change to the rate of SD mishaps. The Air Force has the same graph: another Approach
