Since 1954 spatial disorientation has been a significant factor in 4 to 10 percent of all major accidents. Spatial disorientation or "pilot vertigo" is a a condition which exist when a pilot can't accurately determine the location of the surface of the Earth. All pilots are susceptible to and may experience sensory illusions while flying at night or in certain weather conditions. These illusions can lead to a conflict between actual attitude indications and what the pilot "feels" the attitude in space to be. Disoriented pilots may not be aware of their orientarion error at all. Many crash while busily engaged in some task that takes their attention away from the flight instruments. Others perceive a conflict between their bodily senses and the flight instruments, but crash because they can't resolve the conflict.
It is important to remember that sensory illusions occur regardless of pilot's experience or proficiency. A basic understanding of the organs of equilibrium, the physiological mechanisms of various illusions , and the conditions of flight where these illusions may be expected can help the pilot successfully cope with spatial disorientation.
Of great importance in helping to minimize the effects of spatial disorientation is an understanding of the concepts of visual dominance and vestibular suppression. Visual dominance exists when the pilot receives essentially all of the information used to maintain correct orientation through the eyes. A pilot's ability to accomplish vestibular suppression comes as a result of understanding why spatial disorientation occurs and through disciplined response to the situation.
Time, experience and proficiency make vestibular suppression easier.
Three of our sensory systems are especially important for maintaning equilibrium and balance. These sensory systems function adequately for the normal earthbound activities such as walking, running, jumping, falling, etc., however, when a person is subjected to the environment of air and space, the organs of equilibrium induce errors. These three sensory systems are the VESTIBULAR system, the SOMATOSENSORY system and the VISUAL system.
VISUAL System
The pilott's eyes are most important in maintaing spatial orientation. The ONLY RELIABLE INFORMATION will be provided to the pilot by eyes. On a clear day, when adequate external visual referencia is available , spatial disorientation is unlikely when flying in upright attitudes.
However, given the presence of extreme linear or angular accelerations associated with aircraft attitudes demanded in tactical maneuvering, spatial disiorientation can happen.
Under such circunstances, the availability of a horizon in combination with flight instruments should allow the pilot to more easy maintain visual dominance and naturally suppress vestibular and somatosensory systems.
At night or in Instrument Minimum Conditions flight, the pilot must maintain orientation and a state of visual solely by reference to aircraft instruments, especially Attitude Indicator.
A proficient pilot with an EFFECTIVE INSTRUMENTS CROSS-CHECK will have little difficulty in maintaing visual dominance and ignoring potentially disorientation sensory data.
This is NOT to say that a pilot should NOT look outside the aircraft at night or in Instruments Minimum Conditions flight.
The pilot should BE AWARE that what is seen outside the aircraft under these circunstances may be confusing and could lead to visual illusions and sensory conflicts.
Causes and Effects
When an aircraft accelerates forward, inertia causes the otolithic membrane in the otolith organs to move. This results in the sensation of climbing and cause the pilot to dive in an attempt to compensate for illusory change of attitude.
If a pilot's head moves abruptly during a prolonged turn, the Coriolis Effect can cause an overwhelming illusion of change in aircraft attitude.
If a pilot try correct for your illusion, he or she may put the aircraft in a very dangerous attitude.
Sometimes pilots confuse ground lights with stars.
Sometimes pilots confuse unlighted areas of the Earth with an overcast night sky.
In certain susceptible individuals, unusual sensations can be caused by the passage of light through propellers or rotor blades and by flashing strobe lights. Light flickering at frequencies from 4 to 20 times per second can produce nausea, dizziness, convulsions and even unconsciousness in those individuals.
Types of Desorientation
Type I and Type II
In Type I disorientation, the pilot is oblivious to the fact that he or she is disoriented and controls the airplane completely in accord with and in response to his or her false sensations of attitude and motion.
In Type II disorientation, the pilot realizes that something is wrong with the way the airplane is flying, but may or may not realize that the sorce of the problem is spatial disorientation.
When a pilot is extremely busy manipulating the cockpit controls, anxious, mentally stressed, or fatigued, the pilot's proficiency on instruments flights is decreased.
When a pilot is distracted from cross-check the instruments during task intensive phases of flight in marginal weather or visibility conditions, the pilot's ability to recognize and resist spatial disorientation is severely diminished.
Many spatial disorientation accidents and incidents have been reported during the penetration turn, final approach, climbout after takeoff, trail departures.
Total flying time does not protect an experienced pilot from spatial disorientation.
Education of the pilot begins with an undrestanding of the physiological mechanism that cause various illusions.
Flight surgeons, physiological training officers and flying safety officers can provide additional information through lectures, slide presentations, movies and safety journals about spatial disorientation. Experienced pilots can pass on valuable information to new crewmembers in flight briefings.
Dears fellows, there only must be two rules for successfull flight:
First - Keep your HEADS in the cockpit.
Second - Don't forget any second - "Familiarity breeds contempt".
Flying Training
Instrument Flying Manual