Watching films like Top Gun or Operation: Red Flag the appeal of being a fighter jet pilot, is easily seen, but would the famous actor Tom Cruise have made a real fighter pilot, let alone you or me? The cockpit of a fighter plane is a very restricted and highly hostile environment.
Due to the high altitudes at which they may fly there is little naturally available oxygen and the outside temperature is very low. It’s about 40 to 60 degrees below zero celsius. The movement of the plane can result in severe motion sickness, and the forces produced on to the body by one of the most advanced aerobatic aircraft in the world is very dangerous and literally crushing.
G-force is an instant killer. In fact, the effects of g-force was, as long ago as the Second World War, causing the death of pilots who either lost consciousness or were unable to quickly bail out of their planes.
The ‘g’ in g-force refers to the word ‘gravity’, the force currently allowing you to simply sit down and read this article, and while the force has little to do with gravity, it provides an easily understandable measurement of what g-force really is – essentially acceleration. Most people think of acceleration as an increase in speed.
This is how the word is generally used when thinking about cars and motorbikes, but in purely scientific terms acceleration is a change in velocity (change in speed and/or direction). It’s weird to think that a car that is slowing down or braking or turning a corner is really and truly accelerating if the word was used in its scientific sense.
We measure the force we feel as we accelerate in multiples of gravity – g’s. The force you feel under the influence of gravity is 1g. Put simply, if you were to weigh 80kg (average weight of a man) then at 1g you will still weigh 80kg. That’s why, on the moon, you weigh less than when on earth, because there isn’t gravity. In most people’s day-to-day life they may feel a very small ‘ g ‘ force when accelerating hard, cornering or braking in a car, but that’s nothing when comparing to the average 6g during an aerobatic manoeuvre. In an Extra 300 stunt plane, Zeron and I experienced 6.5g, with quite a fast onset, but only for a few seconds. If we were to go out and play with the big boys in their F-16s we would have to endure over 9g for as long as ten or twenty seconds. All objects exert a gravitational force over one another and this force is unique because it can act over very large distances. On and near the planet Earth, the gravitational force of our planet is so great due to Earth’s large mass that all other gravitational forces are essentially negligible. This force has been calculated to be approximately 9.82 m/s2, and is often called ‘g’, as you likely recall from high school physics class. It is important to note that in accordance with Newton’s Second Law of Motion, F = ma, gravitational force is intimately tied to an object’s mass and varies in direct proportion to this value. For example, gravity on the moon (a much less massive object than earth) is only 1.62 m/s2. When the lift of an aircraft is greater than the force of gravity, controlled flight becomes possible as the Wright Brothers demonstrated to the world in 1903. Gravitational force is the reason why objects drop to the surface of the earth, and is also the force that an aircraft’s airfoils must contend with to create lift. When the lift of an aircraft is greater than the force of gravity, controlled flight becomes possible as the Wright Brothers demonstrated to the world in 1903. On a normal flight, at take off the g force is around 0.4g.
Some terms are –
Grey-out — Loss of peripheral vision (also referred to as tunnel vision) with loss of colour perception, and no loss of consciousness, The pilot can still hear, feel, and think. Recovery time two to three seconds after release of positive G force.
Blackout — Complete loss of eyesight, no loss of consciousness. Pilot can hear, feel, and think. Recovery time two to three seconds after release of positive G force.
L.O.C. — Loss of consciousness. The subject cannot hear, feel, think, or function. Frequently accompanied by seizure activity and/or loss of bladder and bowel control. Recovery does not occur on the average for 15 to 20 seconds after the G force is terminated. The time required to return to consciousness may vary from nine to 20 seconds, and the subject does not re- turn to normal function for several minutes. Very dangerous.
+ G — Positive G forces exerted through the vertical axis of the body. The effect of positive G loading (± G is a function of the G load, the time exposed to the G load, and the rate at which the G load is produced.
[CSSBUTTON target=”http://www.migflug.com/jet-fluege/flugzeuge/l-39-albatros.html” color=”#F22F2C”]Want to experience some Gs yourself?[/CSSBUTTON]
Additional Readings –
Author – Jake Meilak