For anyone training to become modern fighter pilot, a trip in the centrifuge must be something to dread and an experience to remember. Unfortunately for them, in order to fly they have little choice but to attain their G-Rating.
With even relatively old aircraft like the F-16 Fighting Falcon able to maintain sustained 9g manoeuvres, a pilot’s ability to withstand the extreme forces exerted on him during high-g flight is paramount as, in a dog fight, his ability to withstand these forces whilst remaining alert could be the difference between life and death.
With modern combat aircraft becoming evermore agile – the Russian SU27 being a prime example (the aircraft featured in the header image) – it would be true to say that the weakest, limiting factor in any fighter aircraft is now the pilot. And, whilst cumbersome G-suits can certainly help the pilot remain compus mentus the barrier still remains – though such suites can help pilots to sustain levels as high as 12g albeit it only for exceedingly brief periods.

An F-16 Fighting Falcon Pulling G’s
In essence, a single “G” is defined by the force of gravity as exerted on the human body whilst they remain at a standstill on the ground. For every further g the human body is exposed to their body weight is multiplied by the number of g’s being experienced.
For example, assuming that you weigh 189lbs (85kg) – the average weight of a mid-life male – your weight, as experienced, would be the following based on the g-load factor being placed upon you.
2G – 378lbs (171kg)
3G – 567lbs (257kg)
4G – 756lbs (348kg)
5G – 945lbs (429kg)
6G – 1134lbs (514kg)
7G – 1323lbs (600kg)
8G – 1512lbs (685kg)
9G – 1701lbs (776kg)
10G – 1890lbs (857kg)
11G – 2079lbs (943kg)
12G – 2268lbs (1028kg)
To put this into stark perspective, an average adult cow weighs between 1,100 and 1,500 pounds so a fighter pilot pulling only 8g’s is already experiencing a comparable bodyweight, and the equivalent strain on his organs and skeleton.

A Pilot in his G-Suit
The main problem with pulling extreme g’s is either too much or too little blood flowing around the brain, and there are two types of g-force related problems that pilot’s brains have to endure – these are known as black-out and red-out. Black-out occurs when too little blood is entering the brain as a result of extreme positive g-forces whereas Red-out occurs when too much blood is being pumped around the brain, and this occurs in high negative environments. For example, a pilot pulling one negative g – which can be simply induced by nosing an aircraft over – is already experiencing weightlessness (such as experienced by astronauts).
It is an interesting fact that pilots who adjust their seat so that their helmets are just touching the canopy find that, subsequent to flying a profile of high-g manoeuvres, they are actually able to notch the seat up on landing due to compression of the spine.
Lets see g-forces in action.
In this video you can see pilots experiencing high g’s in the centrifuge with the level of g being experienced being indicated by the figure in the top left hand corner. What is extremely evident in this video is how the pilots strain against the forces being exerted on them. Literally referred to as “straining” the pilots attempt to keep as much of their blood in their body – as opposed to it welling up in their legs – by clenching their abdominal muscles. The exercise is apparently very much comparable to straining on the toilet.
Interested in aviation? You might find this post interesting – featuring a video of heavy crosswind landings. Alternately, you might want to take a trip through a jet engine courtesy of Rolls Royce via this page.
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“Video of G-Forces in Action”
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That video made me laugh out loud! Interesting and funny at the same time.