A g-suit, or anti-g suit, is a flight suit worn by aviators and astronauts who are subject to high levels of acceleration force (g). It is designed to prevent a black-out and g-LOC (g-induced loss of consciousness) caused by the blood pooling in the lower part of the body when under acceleration, thus depriving the brain of blood. [1] Black-out and g-LOC have caused a number of fatal aircraft accidents. [2]
If blood is allowed to pool in the lower areas of the body, the brain will be deprived of blood. This lack of blood flow to the brain first causes a greyout (a dimming of the vision also called brownout), followed by tunnel vision and ultimately complete loss of vision 'blackout' followed by g-induced Loss Of Consciousness or 'g-LOC'. The danger of g-LOC to aircraft pilots is magnified because on relaxation of g-force there is a period of disorientation before full sensation is re-gained. A g-suit does not so much increase the g-threshold, but makes it possible to sustain high g longer without excessive physical fatigue. The resting g-tolerance of a typical person is anywhere from 3–5 g depending on the person. A g-suit will typically add 1 g of tolerance to that limit. Pilots still need to practice the 'g-straining maneuver' that consists of tensing the abdominal muscles in order to tighten blood vessels so as to reduce blood pooling in the lower body. High g is not comfortable, even with a g-suit. In older fighter aircraft, 6 g was considered a high level, but with modern fighters 9 g or more can be sustained structurally[ citation needed ] making the pilot the critical factor in maintaining high maneuverability in close aerial combat.[ citation needed ]
A g-suit is a special garment and generally takes the form of tightly fitting trousers, which fit either under or over (depending on the design) the flight suit worn by the aviator or astronaut. The trousers are fitted with inflatable bladders which, when pressurized through a g-sensitive valve in the aircraft or spacecraft, press firmly on the abdomen and legs, thus restricting the draining of blood away from the brain during periods of high acceleration. In addition, in some modern very high-g aircraft, the Anti-g suit effect is augmented by a small amount of pressure applied to the lungs (positive pressure breathing), which also enhances resistance to high G. The effects of anti-g suits and positive pressure breathing are straightforward to replicate in a simulator, although only continuous g can be produced artificially in devices such as centrifuges. [3]
Various designs of g-suit have been developed. They first used water-filled bladders around the lower body and legs. Later designs used air under pressure to inflate the bladders. These g-suits were lighter than the liquid-filled versions and are still in extensive use. However, the Swiss company Life Support Systems AG and the German Autoflug collaborated to design the new Libelle suit for use with the Eurofighter Typhoon aircraft, which reverts to liquid as the medium and improves on performance. The Libelle suit is under consideration for adoption by the United States Air Force. [4]
As early as 1917, there were documented cases of pilots' loss of consciousness due to g (G-LOC) that were referred to as "fainting in the air". [5] [6]
The recognition that the tight turns required of RAF High Speed Flight pilots taking part in 1920s Schneider Trophy races causing blackouts meant a restriction to 4G to limit them to "grey out" with only partial loss of vision. [7]
In 1931 a professor of physiology, Frank Cotton, from the University of Sydney described a new way of determining the center of gravity of the human body. This made it possible to describe the displacement of mass within the body under acceleration. [8] Cotton had recognised the need for an anti-gravity suit during the 1940 Battle of Britain. It was estimated that 30% of pilot deaths were due to accidents, including black-out. Supermarine Spitfires, in particular, were capable of rapid turns that generated high g-forces, causing black-out when diving to fire or avoid enemy fire. [9]
With the development of higher speed monoplane fighters in the late 1930s, acceleration forces during combat became more severe. [6] [10] As early as 1940 some aircraft had foot-rests above the rudder pedals so that the pilot's feet and legs could be raised during combat in an attempt to minimize the negative effects of high speed turns. Large rudder deflections were often not necessary during such manoeuvres, but being able to cut inside the opponent's turning radius was.[ citation needed ]
Wilbur R. Franks had suggested water-filled system in 1938 and in the absence of government funding he built a prototype - sized on himself - with private funding but his work was limited by availability of a suitable aircraft. In 1940 the UK provided a Supermarine Spitfire to aid his research. [7] The first g-suits [11] were developed by a team led by Franks at the University of Toronto's Banting and Best Medical Institute in 1941. [12] The suits were manufactured by the Dunlop company and first used operationally in 1942 by pilots of 807 Squadron Fleet Air Arm (FAA) flying Supermarine Seafires during the Operation Torch [13] invasion of North Africa. These devices used water-filled bladders around the legs; two Marks (versions) were developed:
Adoption of the suit by the RAF was limited, as there was concern about pilots exceeding the stress limits of their aircraft and the possibility of revealing its existence to the enemy. [7]
Professor Frank Cotton of Sydney University, Australia, designed the first successful gas-operated anti-G suit. [14] Research commenced late in 1940, and a suit was designed with rubber sacs covered externally by inextensible material. The sacs automatically inflated when G forces increased during flying. The suit was developed at the Sydney Medical School. Cotton constructed the first human centrifuge in the Anderson Stuart Building at Sydney University under tight wartime security. The volunteers, young airmen, were strapped by their legs to the centrifuge and subjected to high g-force and monitored until black-out occurred. All lost consciousness. On February 19, 1942, the day of the major Japanese bombing of Darwin, Cotton's suit was approved by the Allied war chiefs. The Americans soon issued orders for manufacture of a suit based on Cotton's design. [15] The Cotton suit was later flight-tested in a Hurricane, Kittyhawks, and Spitfires and provided about 2G protection. It was examined by RAF Physiological Laboratory and the Royal Air Force ran competitive trials of the Cotton Anti-G suit with the Frank G-Suit that was already adopted in 1944. The Franks suit was self-contained, production contracts prepared and there was insufficient capacity to develop both simultaneously so the RAF was not able to take it on but recommended the RAAF did. [7] The Royal Air Force concluded that: "There is no doubt the Cotton Suit gives the best protection." The Cotton suit's use of gas-inflatable bladders is still used in the modern anti-G suit. [14]
In the United States, physiologists Drs. Earl H. Wood, Edward Baldes, Charles Code and Edward H. Lambert, working in a top-secret research lab at the Mayo Clinic, helped to define the specific physiologic effects causing blackout and unconsciousness during high G forces. Based upon their new understanding of the physiologic effects of high G-forces, they developed a more practical G-suit derived from the work of Cotton and Franks. This suit used inflation like the Cotton suit. While Professor Cotton's design was intriguing, he was more focused on the center of gravity than on blood flow. This latter point was the key to making a practical anti-g suit that could be worn in combat. [12] This suit was worn by US pilots towards the end of World War II. [11] [16] [17] [18] [19]
The researchers were part of a team assembled at the Mayo Clinic investigating the effects of high-performance flight on military pilots, by studying the physiological effects of flight and how to mitigate them. They used a large centrifuge to whirl riders and observe their blood pressures at the head and heart levels with special instruments. To prevent drops in blood pressure, the team designed an air bladder suit that inflated the pilot's calves, thighs, and abdomen. [20] A primary contribution, allowing for the shift from pulsatile water-filled bladders to non-pulsatile air-filled bladders, made by the Mayo investigators was to show that maintenance of arterial pressure rather than venous return was required to maintain perfusion of the eyes and brain. [21] Prototypes of the GPS suits were known as the "arterial Occlusion Suit" (AOS) or the Clark-Wood suit, named after Wood and Dave Clark (head of the Dave Clark company who fabricated the early suits for the team at Mayo) [22]
Their efforts finally culminated with the release of the first US military design in late 1943: the GPS (Gradient Pressure Suit) type fighter pilot's G-1 anti-g-suit. [23] The team subsequently worked on developing further, more advanced models in 1944 and beyond. [23]
Although uncomfortable and distracting to use, later research showed that military fighter pilots who wore g-suits survived and defeated their opponents in greater numbers than those who didn't. [19]
Modern g-Suits meet the United States Air Force Standard CSU-13B/P and United States Navy Standard CSU 15 A/P.
During World War II the German Henschel Hs 132 (never flew) and the US Northrop XP-79 (crashed on first powered flight) jets both had prone positions to minimize blood pooling in the legs. [24] After 1945 the British experimented with prone flying positions in a highly modified Gloster Meteor F8 jet fighter and the Reid and Sigrist R.S.3 "Bobsleigh" a piston engined trainer. However, other difficulties associated with prone piloting and the development of practical g-suits for normal seating positions terminated these experiments.
A similar concept, the supine cockpit exists.
Air-based g-suits were very common in NATO aircraft of all nations from the 1950s onwards and are still in common use today.[ citation needed ]
Later jets such as the McDonnell Douglas F-15 Eagle, General Dynamics F-16 Fighting Falcon, Boeing F/A-18 Super Hornet, Eurofighter Typhoon and the Dassault Rafale can sustain high g loads for longer periods, and are therefore more physically demanding. By using a modern g-suit in combination with anti-g strain techniques, a trained pilot is now expected to endure accelerations of up to nine g without blacking out.[ citation needed ]
Astronauts wear g-suits similar to aviators but face different challenges due to the effects of microgravity. Aviator g-suits apply uniform pressure to the lower legs to minimize the effects of high acceleration but research from the Canadian Space Agency [25] implies there might be a benefit in having a suit for astronauts that uses a "milking action" to increase blood flow to the upper body.[ citation needed ]
Pilots in Red Bull Air Race World Championship have worn a g-suit called g-Race Suit since the 2009 season. The g-race suit is a liquid (water) filled, autonomous and aircraft independent working full-body g-protection system. It is tailor-made for each pilot and can be fine adjusted via lacings.[ citation needed ]
The g-race suit contains four so-called "fluid muscles" which are sealed, liquid-filled tubes. Each fluid muscle extends from the shoulder to the ankle. Two fluid muscles – each filled with approximately 1 litre of fluid for a total of around 4 litres (1.1 US gal) per g-race suit – are routed vertically on the front side of the g-race suit and two are routed vertically on the rear side of the g-race suit. The suit weighs on average 6.5 kilograms (14 lb) in total, and its fabric is made out of a special mix of Twaron and Nomex. The counter pressure effect occurs instantaneously without any time delay versus an up to two second delay before reaching full system protection in standard pneumatic, inflatable g-suits. The race pilot utilizes the g-race suit interactively by muscle straining and breathing techniques to achieve an improved cardiac output and thus improved G-protection. [26]
A centrifuge is a device that uses centrifugal force to subject a specimen to a specified constant force - for example, to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby separating fluids of different densities or liquids from solids. It works by causing denser substances and particles to move outward in the radial direction. At the same time, objects that are less dense are displaced and moved to the centre. In a laboratory centrifuge that uses sample tubes, the radial acceleration causes denser particles to settle to the bottom of the tube, while low-density substances rise to the top. A centrifuge can be a very effective filter that separates contaminants from the main body of fluid.
The g-force or gravitational force equivalent is mass-specific force, expressed in units of standard gravity . It is used for sustained accelerations, that cause a perception of weight. For example, an object at rest on Earth's surface is subject to 1 g, equaling the conventional value of gravitational acceleration on Earth, about 9.8 m/s2. More transient acceleration, accompanied with significant jerk, is called shock.
Aviation medicine, also called flight medicine or aerospace medicine, is a preventive or occupational medicine in which the patients/subjects are pilots, aircrews, or astronauts. The specialty strives to treat or prevent conditions to which aircrews are particularly susceptible, applies medical knowledge to the human factors in aviation and is thus a critical component of aviation safety. A military practitioner of aviation medicine may be called a flight surgeon and a civilian practitioner is an aviation medical examiner. One of the biggest differences between the military and civilian flight doctors is the military flight surgeon's requirement to log flight hours.
Wilbur Rounding Franks, OBE was a Canadian scientist, notable as the inventor of the anti-gravity suit or G-suit, and for his work in cancer research.
Artificial gravity is the creation of an inertial force that mimics the effects of a gravitational force, usually by rotation. Artificial gravity, or rotational gravity, is thus the appearance of a centrifugal force in a rotating frame of reference, as opposed to the force experienced in linear acceleration, which by the equivalence principle is indistinguishable from gravity. In a more general sense, "artificial gravity" may also refer to the effect of linear acceleration, e.g. by means of a rocket engine.
An oxygen mask is a mask that provides a method to transfer breathing oxygen gas from a storage tank to the lungs. Oxygen masks may cover only the nose and mouth or the entire face. They may be made of plastic, silicone, or rubber. In certain circumstances, oxygen may be delivered via a nasal cannula instead of a mask.
A flight suit is a full-body garment, worn while flying aircraft such as military airplanes, gliders and helicopters. These suits are generally made to keep the wearer warm, as well as being practical, and durable. Its appearance is usually similar to a jumpsuit. A military flight suit may also show rank insignia. It is sometimes used by Special Forces as a combat uniform in close quarters battle or visit, board, search, and seizure situations, for its practicality.
A pressure suit is a protective suit worn by high-altitude pilots who may fly at altitudes where the air pressure is too low for an unprotected person to survive, even when breathing pure oxygen at positive pressure. Such suits may be either full-pressure or partial-pressure. Partial-pressure suits work by providing mechanical counter-pressure to assist breathing at altitude.
Aerosinusitis, also called barosinusitis, sinus squeeze or sinus barotrauma is a painful inflammation and sometimes bleeding of the membrane of the paranasal sinus cavities, normally the frontal sinus. It is caused by a difference in air pressures inside and outside the cavities.
g-force induced loss of consciousness is a term generally used in aerospace physiology to describe a loss of consciousness occurring from excessive and sustained g-forces draining blood away from the brain causing cerebral hypoxia. The condition is most likely to affect pilots of high performance fighter and aerobatic aircraft or astronauts but is possible on some extreme amusement park rides. 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, with some profiles exposing pilots to 9 gs for a sustained period.
A fighter pilot or combat pilot is a military aviator trained to engage in air-to-air combat, air-to-ground combat and sometimes electronic warfare while in the cockpit of a fighter aircraft. Fighter pilots undergo specialized training in aerial warfare and dogfighting. A fighter pilot with at least five air-to-air kills becomes known as an ace.
A greyout is a transient loss of vision characterized by a perceived dimming of light and color, sometimes accompanied by a loss of peripheral vision. It is a precursor to fainting or a blackout and is caused by hypoxia, often due to a loss of blood pressure.
High-g training is done by aviators and astronauts who are subject to high levels of acceleration ('g'). It is designed to prevent a g-induced loss of consciousness (g-LOC), a situation when the action of g-forces moves the blood away from the brain to the extent that consciousness is lost. Incidents of acceleration-induced loss of consciousness have caused fatal accidents in aircraft capable of sustaining high-g for considerable periods.
David Clark Company, Inc. (DCC) is an American manufacturing company. DCC designs and manufactures a wide variety of aerospace and industrial protective equipment, including pressure-space suit systems, anti-G suits, headsets, and several medical/safety products. DCC has been involved in the design and manufacture of air-space crew protective equipment since 1941, beginning with the design and development of the first standard anti-G suits and valves used by allied fighter pilots during World War II.
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g or, incorrectly, zero gravity.
Earl Howard Wood was an American cardiopulmonary physiologist who helped invent the G-suit, brought heart catheterization into a clinical reality and introduced dynamic volumetric computed tomography for the study of the heart and lungs.
The United States Air Force School of Aerospace Medicine (USAFSAM) is the United States Air Force (USAF) organization focused on education, research, and operational consultation in aerospace and operational medicine. USAFSAM was founded in 1918 to conduct research into the medical and physiologic domains related to human flight, and as a school for medical officers trained to support military aviation operations, later coined as flight surgeons. The school supported early military aviation from World War I through the evolution of aviation and into the modern era. USAFSAM conducted medical research and provided medical support for the initial US space operations beginning in 1947 through the establishment of NASA in 1958. After the creation of NASA, USAFSAM continued to actively support civilian and military manned space missions through clinical and physiologic research. USAFSAM is one of the oldest continually operating school for flight surgeons and other operational medical personnel of its kind in the world. USAFSAM is located in Dayton, Ohio at Wright-Patterson Air Force Base, and is part of the 711th Human Performance Wing and the Air Force Research Laboratory (AFRL).
Locomotion in space includes all actions or methods used to move one's body in microgravity conditions through the outer space environment. Locomotion in these conditions is different from locomotion in a gravitational field. There are many factors that contribute to these differences, and they are crucial when researching long-term survival of humans in space.
The VKK flight suit, is a series of Soviet high-altitude partial pressure suit, which loosely translates 'altitude compensation suit'. It has been the standard issue for pilots of both the Soviet Air Forces and the Russian Aerospace Forces for jet aircraft since 1958.
Edward Lambert was an American neurophysiologist, best known for his description of the Lambert–Eaton myasthenic syndrome and regarded as one of the founders of electromyography.
