G-Force Nightmare: How Fighter Pilots Cheat Death Every Time They Pull 9 G’s – SOFREP News Team
“After dinner, the weather being warm, we went into the garden and drank thea, under the shade of some apple trees…he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. It was occasion’d by the fall of an apple, as he sat in contemplative mood. Why should that apple always descend perpendicularly to the ground, thought he to himself…”
This simple moment of reflection led Sir Isaac Newton to uncover the mysterious force of gravity, setting the stage for centuries of scientific progress. And, as fighter aircraft took to the skies, Newton’s laws of motion and gravitation were soon harnessed for tactical advantage.
The Force Of Gravity
Gravity is an accelerating force, which means it acts on objects to change their velocity. Every object exerts a gravitational force on others, and what makes gravity unique is its ability to influence objects across vast distances. On Earth, this force is overwhelmingly dominated by the planet’s mass, which is why we feel Earth’s gravitational pull so strongly, making all other forces negligible by comparison.
This gravitational acceleration is approximately 9.82 m/s², commonly referred to as ‘g,’ a concept you likely encountered in high school physics.
As per Newton’s Second Law of Motion (F = ma), gravitational force is directly related to an object’s mass. For instance, gravity on the Moon is only 1.62 m/s² due to its much smaller mass compared to Earth. This gravitational force is why objects fall to Earth and why aircraft must counteract gravity with lift. When the lift produced by an aircraft exceeds the force of gravity, flight becomes possible, as demonstrated by the Wright Brothers in 1903.
G-Force Lingo and Notation
Humans, like all life on Earth, have adapted to the gravitational pull of our planet. For simplicity, let’s call this standard gravitational force (9.82 m/s²) 1G. However, during flight, it’s possible to experience forces greater or less than 1G. When we say a pilot is “pulling 3 Gs,” they are experiencing three times the normal gravitational force. So, if someone weighs 150 lbs at 1G, they would weigh 450 lbs at 3Gs — quite a heavy load!
The human body is not accustomed to such changes, and our physiology must respond accordingly. When an aircraft is accelerating toward the Earth, it’s not just influenced by Earth’s gravity but also by the forces applied during flight. Newton’s First Law of Motion helps explain why the body wants to continue moving in a straight line unless external forces (like seat restraints) act to change that motion.
In flight, these forces are experienced along different axes: x, y, and z. G-forces in the z-axis (Gz) are the most common and most impactful, particularly in terms of how they affect the human body. The x-axis (Gx) impacts primarily during launch or when an aircraft is turning, while the y-axis (Gy) becomes more relevant with newer multi-directional thrust jets, like the F-22 and SU-35.
“After dinner, the weather being warm, we went into the garden and drank thea, under the shade of some apple trees…he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. It was occasion’d by the fall of an apple, as he sat in contemplative mood. Why should that apple always descend perpendicularly to the ground, thought he to himself…”
This simple moment of reflection led Sir Isaac Newton to uncover the mysterious force of gravity, setting the stage for centuries of scientific progress. And, as fighter aircraft took to the skies, Newton’s laws of motion and gravitation were soon harnessed for tactical advantage.
The Force Of Gravity
Gravity is an accelerating force, which means it acts on objects to change their velocity. Every object exerts a gravitational force on others, and what makes gravity unique is its ability to influence objects across vast distances. On Earth, this force is overwhelmingly dominated by the planet’s mass, which is why we feel Earth’s gravitational pull so strongly, making all other forces negligible by comparison.
This gravitational acceleration is approximately 9.82 m/s², commonly referred to as ‘g,’ a concept you likely encountered in high school physics.
As per Newton’s Second Law of Motion (F = ma), gravitational force is directly related to an object’s mass. For instance, gravity on the Moon is only 1.62 m/s² due to its much smaller mass compared to Earth. This gravitational force is why objects fall to Earth and why aircraft must counteract gravity with lift. When the lift produced by an aircraft exceeds the force of gravity, flight becomes possible, as demonstrated by the Wright Brothers in 1903.
G-Force Lingo and Notation
Humans, like all life on Earth, have adapted to the gravitational pull of our planet. For simplicity, let’s call this standard gravitational force (9.82 m/s²) 1G. However, during flight, it’s possible to experience forces greater or less than 1G. When we say a pilot is “pulling 3 Gs,” they are experiencing three times the normal gravitational force. So, if someone weighs 150 lbs at 1G, they would weigh 450 lbs at 3Gs — quite a heavy load!
The human body is not accustomed to such changes, and our physiology must respond accordingly. When an aircraft is accelerating toward the Earth, it’s not just influenced by Earth’s gravity but also by the forces applied during flight. Newton’s First Law of Motion helps explain why the body wants to continue moving in a straight line unless external forces (like seat restraints) act to change that motion.
In flight, these forces are experienced along different axes: x, y, and z. G-forces in the z-axis (Gz) are the most common and most impactful, particularly in terms of how they affect the human body. The x-axis (Gx) impacts primarily during launch or when an aircraft is turning, while the y-axis (Gy) becomes more relevant with newer multi-directional thrust jets, like the F-22 and SU-35.
Human Physiology In Response To Gravity
The circulatory system is the most affected by G-forces during flight. At standard 1G, blood tends to pool in the lower extremities. When G-forces increase, especially in the +Gz direction (towards the Earth), blood is forced away from the brain and toward the lower body, causing a lack of oxygenated blood in the brain. This condition, known as cerebral hypoxia, results in a loss of consciousness, or G-LOC (G-induced Loss of Consciousness).
In the 1990s, the US Air Force lost about one aircraft per year to G-LOC. This is why fighter pilots undergo extensive G-force training, often involving centrifuge simulations to help them tolerate and manage these extreme conditions.
Increased +Gz also disrupts respiration by forcing blood into the lung bases, reducing the amount of air that can exchange oxygen, further contributing to the risk of hypoxia.
The G-LOC Phenomenon
G-LOC occurs when a pilot experiences an interruption in cerebral blood flow due to excessive G-forces.
Symptoms typically start with visual disturbances, such as tunnel vision, followed by “graying out” or a complete blackout as the retina receives insufficient oxygen.
If the G-force exceeds the body’s ability to compensate, the result is unconsciousness. After regaining consciousness, the pilot may experience a brief period of confusion and memory loss, often accompanied by muscle convulsions (colloquially called “funky chicken“).
Combatting G-LOC: The Anti-G Straining Maneuver (AGSM)
To combat the effects of G-forces, aircrews are trained in the Anti-G Straining Maneuver (AGSM), which involves isometric muscle contractions and controlled breathing to maintain adequate blood flow to the brain.
When combined with a G-suit, which inflates to compress the lower body and prevent blood from pooling there, pilots can withstand higher G-forces without losing consciousness.
Historically, without an AGSM or G-suit, pilots could experience G-LOC at around 5.4 Gs. However, modern techniques have allowed pilots to remain conscious at up to +9Gz, thanks to improved suits like the ATAGS (Anti-G Suit).
Transient Forces
While the focus here has been on sustained G-forces, it’s important to mention transient forces. These are short bursts of acceleration or deceleration, such as during a crash or ejection sequence.
These forces carry a high risk of blunt trauma and are another significant factor in aviation safety.
Conclusion
Gravity is a constant in our lives, but in aviation, it can become both a challenge and a tool. Understanding the effects of G-forces, how the body responds, and how modern pilots train to withstand them, helps highlight the incredible demands placed on human physiology in the pursuit of high-speed flight. Whether it’s the challenge of G-LOC or the technology of G-suits, the quest to conquer gravity continues to push the limits of aviation.
—
This piece was originally published in 2019 and has been updated for clarity and accuracy.
