G-forces don't translate to the big screen, or to video games, but they are a major aspect of flying fighters. Movies like Top Gun show the characters easily moving around the cockpit while chatting on the radio during a dogfight. In reality, during a sharp turn under peak G, you're spending the majority of your effort pancaked into your seat, trying not to pass out.
Right now, as you're reading this, you're probably at 1G, or one time the force of gravity. Your weight is what you see when you stand on a scale. I weigh approximately 200 pounds, 230 with my gear on. For most people, the peak G-force they've experienced is probably on a rollercoaster during a loop—which is about 3-4G's. It's enough to push your head down and pin your arms by your side. Modern fighters like the F-16 and F-35 pull 9G's, which translates to over 2,000 pounds on my body.
(U.S. Air Force photo/Senior Airman Patrick P. Evenson)
Under 9G's, the world appears to shrink until it looks like you're viewing it through a toilet paper roll. Blood is being pulled out of your head towards your legs and arms, resulting in the loss of peripheral vision. If too much blood is pulled out, you'll pass out, resulting in incapacitation for around half a minute. Due to the speeds we fly, there's a high probability the jet will crash before you wake up.
As a fighter community we, unfortunately, have had more than one death per year, due to G's, for the last 30+ years. This has led to a multi-pronged "systems mindset" for preparing pilots to endure them.
The first step in combating G's is the Anti-G Straining Maneuver (AGSM). Through a combination of special breathing and tensing our lower body we can squeeze the blood back into our head. This not only prevents us from passing out, but increases our peripheral vision, which is critical during a dogfight.
The AGSM requires a high amount of physical conditioning. We spend a lot of time in the gym, working out our lower bodies, so we can push the blood against the force of gravity during high-G maneuvers. Because our flights average one to two hours, cardiovascular fitness is important as well. During my time in the F-16, I gave a dozen, or so, people backseat rides—after the flight, due to exhaustion, every one of them had to be helped out of their seat.
Hydration and nutrition also play an important part in the amount of G's a pilot can handle. Studies have shown that with only three percent dehydration, G-tolerance time can be reduced by up to 50%. As with any athletic endeavor, it's important we eat nutritious foods and avoid high sugar "junk food."
Sleep is also a contribution factor to G-tolerance. Poor sleep decreases alertness and G-awareness, which is what signals a pilot to start their G-strain. In fact, it's so important that we're legally required to go into crew rest 12 hours before a flight, with an uninterrupted 8 hours to sleep.
Over the years, technology has allowed us to pull more G's for longer amounts of time. We wear G-suits, which are pants with air-bladders in them. As we enter a turn, the bladders inflate, squeezing our legs and preventing blood from rushing towards our feet. To increase endurance, we have pressure-breathing, which forces air into our lungs during high-G's. Instead of struggling for a breath, with what feels like an elephant on our chest, we can take a small sip of air and rely on the pressure-breathing to fill our lungs.
The current G-suit is shown on the left, with the older version on the right.
(U.S. Air Force photo by Staff Sgt. C.J. Hatch)
After high-G flights, my arms and legs will have what appears to be chickenpox—blood has pooled in my extremities and caused the blood vessels to rupture. It's similar to a bruise and usually dissipates within a few days. The long term effects of high-G's can result in neck and back issues—most pilots deal with some level of general pain due to G's.
With our helmets on, over 135 pounds of force is applied to the neck at 9G's. In my squadron of 30 people: one pilot is unable to fly while his neck heals, another has been told by the flight doctor that he has the spine of someone in their mid-fifties (he's 39), and another is only able to fly low-G sorties. A few months ago, I had to get X-rays on my back to determine if I'd damaged a vertebra. As a community, we've started to introduce physical therapy and dedicated stretching routines after each flight, in order to extend our careers.
I often get asked why we can't do all of our training in a simulator—G's are one of the reasons why. It's one thing to make decisions sitting on the ground, it's another when you feel the world closing in as the blood is being drained from your head. One of the sayings we have in the fighter community is: as soon as you put the helmet on, you lose 20 IQ points. During a max performance turn, without extensive training, it's probably a lot more.