G-LOC, pronounced 'GEE-lock', is the abbreviation of G-force induced Loss Of Consciousness, a term generally used in aerospace physiology to describe a loss of consciousness occurring from excessive and sustained g-forces The gravitational force, or g-force, on something is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces. Accelerations not produced by gravity are termed proper accelerations, and cause stresses and strains on objects. Because of these strains, large g-forces may draining blood away from the brain causing cerebral hypoxia Hypoxia is a pathological condition in which the body as a whole or a region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise. A mismatch between oxygen supply and its demand at the cellular level. The condition is most likely to affect pilots An aviator is a person who flies or travels via aircraft for pleasure or as a profession. The first recorded use of the term was in 1887 as a variation of 'aviation', from the Latin 'avis' (meaning bird), coined 1863 by G. de la Landelle in "Aviation ou Navigation Aérienne" ('Aviation or Air Navigation'. The term aviatrix (aviatrice in of high performance fighter A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets by dropping bombs. Fighters are small, fast, and maneuverable. Many fighters have secondary ground-attack capabilities, and some are dual-roled as fighter-bombers; the and aerobatic Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in normal flight. Aerobatics are performed in airplanes and gliders for training, recreation, entertainment and sport. Some helicopters, such as the MBB Bo 105, are capable of limited aerobatic maneuvers aircraft or astronauts An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft. While generally reserved for professional space travelers, the term is sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists but is possible on some extreme amusement park rides The gravitational force, or g-force, on something is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces. Accelerations not produced by gravity are termed proper accelerations, and cause stresses and strains on objects. Because of these strains, large g-forces may. G-LOC incidents have caused fatal accidents in high performance aircraft capable of sustaining high g for extended periods. High-G training for pilots of high performance aircraft or spacecraft often includes ground training for G-LOC in special centrifuges A centrifuge is a piece of equipment, generally driven by an electric motor , that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis. The centrifuge works using the sedimentation principle, where the centripetal acceleration causes more dense substances to separate out along the radial direction (the bottom, with some profiles exposing pilots to 9 gs for a sustained period. Such man-rated centrifuges are made by AMST Systemtechnik in Austria (Austria Metall SystemTechnik), Latacoere in France, the Environmental Tectonics Corporation (ETC) and Wyle Laboratories in the USA.
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Effects of g-forces
Under increasing positive g-force, blood in the body will tend to move from the head toward the feet. For higher intensity or longer duration, this can manifest progressively as:
- Greyout - a loss of color vision
- Tunnel vision - loss of peripheral vision, retaining only the center vision
- Blackout - a complete loss of vision but retaining consciousness.
- G-LOC - where consciousness is lost.
(Under negative g, blood pressure will increase in the head, running the risk of the dangerous condition known as redout, with too much blood pressure in the head and eyes.)
The reason why vision is affected before other brain functions is because intraocular pressure Intraocular pressure is the fluid pressure of the aqueous humor inside the eye within the eyes works against blood pressure in the head. Skilled pilots can use this loss of vision as their indicator that they are at maximum turn performance without losing consciousness. Recovery is usually prompt following removal of g-force but a period of several seconds of disorientation may occur. Brief but vivid dreams have been reported to follow G-LOC. If G-LOC occurs at low altitude, this momentary lapse can prove fatal and even highly experienced pilots can pull straight to a G-LOC condition without first perceiving the visual onset warnings that would normally be used as the sign to back off from pulling any more g's.
The human body is much more tolerant of g-force when it is applied laterally Human anatomical terms make up a distinct nomenclature to describe areas of the body, to provide orientation when describing parts of human anatomy, and to distinguish different movements of the body. An understanding of these terms is necessary to study the human body in depth. Many of these terms are also applicable in animal anatomy (across the body) than when applied longitudinally Human anatomical terms make up a distinct nomenclature to describe areas of the body, to provide orientation when describing parts of human anatomy, and to distinguish different movements of the body. An understanding of these terms is necessary to study the human body in depth. Many of these terms are also applicable in animal anatomy (along the length of the body). Unfortunately most sustained g-forces incurred by pilots is applied longitudinally. This has led to experimentation with prone pilot aircraft designs which lies the pilot face down or (more successfully) reclined positions for astronauts.
Another physiological effect that can happen from high levels of sustained gs is a temporary condition that pilots call the 'g-measles', where the skin around the buttocks or other extremities becomes mottled because blood capillaries have been broken from too much pressure.
Thresholds
The g thresholds at which these effects occur depend on the training, age and fitness of the individual. An un-trained individual not used to the G-straining maneuver, can black out between 4 and 6 g, particularly if this is pulled suddenly. A trained, fit individual wearing a g suit and practicing the straining maneuver, can, with some difficulty, sustain up to 9g without loss of consciousness. Prone position designs in aircraft have not proved successful and the problem has been addressed largely by the development of the G-suit.
See also
- G-suit
- Redout
- g-forces The gravitational force, or g-force, on something is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces. Accelerations not produced by gravity are termed proper accelerations, and cause stresses and strains on objects. Because of these strains, large g-forces may
External links
G-LOC, Could It Happen To You?
