- Spatial disorientation is the loss or confusion of one’s sense of position in relation to the surface of the earth.
- Vertigo is a sensation of rotation or spinning of either the individual or his surroundings
Disorientation is a normal response to particular circumstances and no one is immune. We orient ourselves by kinesthetic means using our sense of muscle, bone, and joint movement, by use of our vestibular organs in the ear for balance, and by vision. When we are in contact with the earth, each of these senses contribute to a finely tuned sense of where we are located and what to expect next from a wide range of motions that we make. However, once we start losing physical contact with the earth we become increasingly drawn into situations that require us to compensate intellectually for our lack of adaptation or indeed to replace our genetically ‘wired in’ reactions. If there is any such thing as a ‘natural pilot’ it is most likely a person who is able to absorb and accept the new realities of flight.
What are these new realities? First we must accept that down is where the earth is, and not where the gforces developed by the aircraft would indicate. While the kinesthetic sensors can be useful in feeling what is going on with the aircraft, they are rarely useful at all in determining up and down. For this we must rely on our visual senses and the horizon (real or artificial!). Secondly we are subject to accelerations (producing g-forces) in three dimensions as opposed to primarily two on the ground. These accelerations will be mostly be measured by our vestibular organs in the inner ear. Again we must learn to compensate for these sensations and intellectually separate them from the reality of the actual motion of the aircraft, and not what is really up and down. Sometimes this can be quite difficult as many humans have very close links between their motion sensors and vision. We have come to expect that certain accelerations mean that we have changed the position of our head and are translated into visual expectations. This can mean that we develop illusions that the aircraft has either pitched up or down, or has leaned one way or the other. These can be quite difficult illusions to overcome by purely intellectual means. If we do not move our head and the fluid in our inner ear stops moving, and our brain assumes that the last motions we detected are still in effect. Now if we move our head without a backup visual reference of the correct orientation, our brain assumes that these head movements are actual motions of the aircraft, since it is “part of our body”. The consequence is that we may think that the aircraft is moving in some unpleasant fashion such as a stall, spin, or unwanted dive.
These can be quite powerful illusions and their effects can linger even after we re-establish our visual references. We must learn to accept the evidence presented by our eyes as the truth, not our other sensations. This environment however, can present us with much confusion in the visual realm as well. We have already discussed the problems of a visually expansive environment. Additionally we may be presented with white-out conditions which rob us of our visual cues for up and down. Add to this an environment where accelerations are not reliable indicators of orientation, and we can quickly move into problems of control if we do not have suitable instrumentation and training. As well, our flying world presents us with many different perspectives on the earth that can cause us to misjudge height above ground, length and condition of landing surfaces, and size of obstructions among others. The outcome of this is that we must accept that flying is a learned process and that, we are only “natural” pilots if we are able to learn.