Spatial disorientation can be defined quite simply as the inability to correctly orient oneself with respect to the earth’s surface. It is caused by a variety of sensory illusions. Pilots are especially vulnerable at night and in certain weather conditions. This is because sensory illusions can occur regardless of a pilot’s proficiency or experience.
The body’s sensory system normally provides enough information to our subconscious to adequately orient us for normal, earthbound activity. In the environment of flight, however, the sensory system is no longer as reliable. This is because of the complex motions and forces experienced in flight and the lack of direct visual cues.
In instrument meteorological conditions (IMC) or at night, pilots maintain their orientation almost solely by the visual cues given by select aircraft instruments. Though a pilot should occasionally look out of the cockpit even during IMC, it is important to remember that what is seen outside under IMC conditions could lead to sensory and visual conflicts.
It is important to remember that spatial disorientation can occur during all phases of flight and even on a clear day. Many accidents involving disorientation occur during the takeoff and landing phases of flight. Changes in speed, acceleration, rate of climb or descent and rate of turn can provide false or conflicting sensory inputs. At night the lights on the ground could add to a pilot’s sensory illusions and confusion. Unexpected changes in IMC, or night flying into unfamiliar airports, can affect a pilot’s sensory perception.
Every pilot should be knowledgeable and aware of the effects of spatial disorientation.
There are three types of spatial disorientation:
Type I (Unrecognized): The pilot is oblivious to his or her disorientation, and controls the aircraft completely in accord with and in response to a false orientational perception.
Type II (Recognized): The pilot may experience a conflict between what he feels the aircraft is doing and what the flight instruments show that it is doing.
Type III (Incapacitating): The pilot experiences an overwhelming – i.e. incapacitating – physiologic response to physical or emotional stimuli associated with the disorientation event.
Through the use of flight simulators and training with an instrument flight instructor, information can be gained about how one will react under sensory illusion conditions. Regular time “under the hood” with a qualified flight instructor can also help to develop and maintain proficiency levels that combat spatial disorientation.
In addition, by learning the basics of human physiology and how human sensory systems work, it will be easier to understand what will happen when outside forces, pressures, and variable cues interact with them. When it is recognized early in its development, corrective action can be taken quickly, before aircraft control is jeopardized or lost.