Monday, February 9, 2009

Illusions Leading to Spatial Disorientation.

As a pilot we learn that sometimes the body and it's sensory systems can lie to us.

Everybody, unconsciously, use three sensory systems for orientation: the visual system, the motion sensing system in the inner ear; and the position sensing system involving nerves in the skin, muscles, and joints. With the visual system being the major sensory organ for orientation while moving. All this adds up to a feeling we have about our position and it's situation relative to our surroundings. Simple.

But sometimes through a combination of visual cues, motion, and body movement we can create orientation signals to the brain that are incorrect to our actual orientation and "illusions" happen. In no particular order some of them are:*

The Leans - Basically, a bank may be entered into so slowly that the fluid in the "roll" semicircular tubes in the inner ear aren't set in motion. An abrupt roll correction sets the fluid in motion causing an illusion of a bank in the opposite direction

Coriolis Illusion - An abrupt head movement made during a steady turn may set the inner ear's fluid in motion in more than one semicircular tube creating an illusion of turning or accelerating in an entirely different direction.

Somatogravic Illusion - A rapid acceleration, especially during take off, can create the illusion of being in a nose up attitude. A rapid deceleration can have the opposite effect, with a feeling of being in a nose low, or dive, situation. This is part of why you feel like the airplane is really climbing during takeoff in an airliner. Even though the deck angle may only be 8 or 9 degrees.

Autokinesis - In the dark, a stationary light may appear to move about when stared at for a period of time.

There are others, they all deal with the visual cues, inner ear or body movement not agreeing with the airplane's attitude.

Don't worry, I'm getting to a point here.

Anyway, as pilot's learn to fly, we train to recognise these illusions and cope with them. The biggest of the coping mechanisms is to use the flight instruments and rely upon them. We're trained to ignore what our feelings are telling us and rely on the facts as relayed by our instruments. With very few specific exceptions, the airplanes instruments don't lie and we train to read them and rely on that information.

While our feelings may be saying one thing, if they don't agree with the instruments, we have to disregard them and believe the instruments. Did you get that, feelings are one thing, but they aren't the only thing. And in some cases they may be the wrong thing.

There are other professions that teach that. My career as an engineer is one. Numbers don't lie. Statistics are another thing. I'm sure there are others, but let me get to my point. (Yes, I know, finally. You don't have to sound so relieved.)

That's whats wrong with a lot of people these days. They haven't been trained to tell the difference between their feelings and what the facts are. I've bemoaned the loss of logic and argument classes that used to be taught in school, this is part of the consequences.

Hoplophobes cry that guns are bad and, sometimes psychotically, ignore the fact that crime rates drop in states that allow concealed carry.

They are convinced they are right because they feel that it is so. The facts must be wrong because they feel that they are. So, they merrily go along holding tighter and tighter to their world, railing against reality that must, MUST be wrong, because their feelings tell them so.

What can stop this cycle? I don't know. Try to present the facts and they shut you out with their feelings. Showing them the reality outside their door won't work, they just view it through the colored lenses that their feelings have placed over their eyes. Would a severe shock to the system work? I'd be afraid that it would just cause them to curl tighter into their cocoon of feelings.

Listening to their feelings makes them feel safe. And safe is supposed to be secure and happy. Pilots are trained to overcome that sometimes terrifying sense that relying on outside information for the real situation can cause. The problem is that feeling safe and actually being safe are two very different things. Feeling safe and being safe are as different as a quiet night flight and an abrupt stop followed by a write up in the aviation safety journals.

AC 61-27C - Instrument Flying Handbook, USDoT FAA

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