Find out how fighter pilots prepare to face G-forces, thanks to specific training, G-suits and physiological techniques.

The impact of G-forces on the body of fighter pilots

Fighter pilots are regularly subjected to intense accelerations, expressed in multiples of the acceleration due to Earth’s gravity, denoted “G”. During complex aerial maneuvers, such as sharp turns or sudden changes in altitude, these forces can reach up to 9 G. This means that the pilot is subjected to a force equivalent to nine times his body weight. For example, an 80 kg pilot would feel a pressure of 720 kg on his body.

These extreme forces have significant physiological consequences. Under the effect of positive G forces, the blood is pushed towards the lower limbs, reducing the blood supply to the brain. This reduction can lead to a gradual loss of peripheral vision, known as “grayout”, followed by a total loss of vision, or “blackout”, and potentially a loss of consciousness. These symptoms generally appear between 4 and 5 G for an untrained person.

Negative G forces, although less frequent, push blood towards the head, increasing intracranial pressure. This can cause eye hemorrhages and brain damage. Human tolerance to negative G is generally lower than to positive G, with limits between -2 and -3 G.

The ability to withstand these forces varies from person to person and depends on factors such as physical condition, specific training and the use of suitable equipment. Without adequate preparation, the risks to health and safety in flight are considerable.

Physiological techniques to increase tolerance to G forces

To counter the harmful effects of G forces, fighter pilots adopt specific techniques aimed at maintaining adequate cerebral perfusion. One of the main methods is the breathing and muscle contraction maneuver, known as Anti-G Straining Maneuver (AGSM).

The AGSM consists of a series of rhythmic muscle contractions, mainly of the leg, abdominal and lower back muscles, synchronized with controlled breathing. These contractions increase blood pressure, helping to maintain blood flow to the brain despite high G forces. Specific breathing, characterized by forced exhalations and brief inhalations, is also used to stabilize intrathoracic pressure.

The effectiveness of AGSM is significant. When properly executed, this technique can increase tolerance to G-forces by an additional 2 to 3 Gs. However, it requires rigorous training to be mastered and effective in real-life situations.

At the same time, optimal physical condition is essential. A robust cardiovascular system and developed musculature improve the body’s ability to resist G forces. Pilot training programs therefore include muscle-strengthening exercises, particularly for the lower limbs and core, as well as cardiovascular activities to improve endurance.

It is also crucial to note that tolerance to G forces can be affected by factors such as fatigue, dehydration and alcohol. Pilots must therefore adopt a strict lifestyle to optimize their in-flight performance.

Equipment and technologies for protection against G forces

In addition to physiological techniques, fighter pilots rely on specialized equipment to mitigate the effects of G-forces. The centerpiece of this protection is the G-suit.

The G-suit is designed to apply pressure to the pilot’s lower limbs and abdomen during high accelerations. It is equipped with inflatable pockets that fill with air or fluid in response to G-forces, compressing the blood vessels in the legs and abdomen. This compression reduces the accumulation of blood in these areas, maintaining adequate cerebral perfusion and preventing blackout and loss of consciousness.

Since its invention by Canadian Wilbur R. Franks in 1941, the anti-G suit has undergone numerous improvements. Modern models, such as the CSU-13 B/P used by the US Air Force, offer effective protection up to 9 G. Recent innovations include lighter materials and more reactive inflation systems, improving the pilot’s comfort and mobility.

In addition, flight simulators and human centrifuges play a crucial role in pilot training. These devices reproduce the G-forces encountered in flight, allowing pilots to get used to the sensations and practice their resistance techniques in a controlled environment. For example, the US Air Force centrifuge can generate forces of up to 9 G, providing realistic and safe training.

By combining this equipment with physiological techniques and rigorous physical preparation, fighter pilots are better prepared to face the challenges posed by G-forces in flight.

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