This is an encore presentation of an Air-Minded post I wrote 13 years ago. I read a brief news report this morning about an Oregon Air National Guard F-15 pilot who experienced GLOC, fortunately recovered in time to save the jet and himself, but unfortunately grossly over-G’ed the airplane in the process (it’s unlikely that particular Eagle will ever fly again). The article mentioned anti-GLOC techniques fighter pilots use, but didn’t mention centrifuge training at all, so I decided it was time to dust this post off and air it again.
Here’s a way to think about pulling Gs and why it hurts: if you weigh 200 pounds, at 9 Gs you’ll weigh 1,800 pounds. Consider that for a moment. Ready for your centrifuge ride?
(apologies for using a non-USAF centrifuge video, but
honestly this is the best one I could find on YouTube)
Fighter pilots have been battling GLOC—G-induced loss of consciousness—since at least WWII, when airplanes began to be capable of pulling more Gs than their human operators. With training, experience, and the right equipment, pilots can withstand high G forces, so long as they anticipate and prepare for them. With rapid G onset (going from 1 to 9 Gs in a second or less, a feat well within the capabilities of modern fighters), even trained and experienced pilots can suffer GLOC.
What happens with GLOC? Basically, the downward force on your body exceeds the ability of your heart to pump blood to the brain. As Gs increase and less blood flows to your brain, you experience tunnel vision, then loss of vision. You’re still conscious, you just can’t see. As Gs continue to increase, though, blood flow stops and you suddenly lose consciousness. As you lose consciousness your body relaxes: you involuntarily quit pulling back on the stick, the Gs go away, and you start to come to.
Your “nap” typically lasts 10 seconds or so. But you don’t come to instantly—after your 10 seconds of unconsciousness, you spend the next 10 to 12 seconds “waking up”—flailing around, unaware of who you are or what you’re doing. Aviators call the waking up phase of GLOC “doing the chicken.” Here’s the downside: if you’re in a dive when you experience GLOC, you may not fully wake up in time to avoid hitting the ground.
How many aircraft and crewmembers have we lost to GLOC? No one really knows, because we didn’t start accurately tracking GLOC incidents and accidents until the 1980s. A good guess, though, is “plenty,” and GLOC continues to be a killer.
We always knew GLOC was a serious problem, and pilots have always trained to combat it. We began using G-suits (inflatable leggings that squeeze against gut, thigh, and calf muscles) and practicing anti-G straining maneuvers (clenching leg, buttock, and stomach muscles while taking short breaths against a closed glottis) shortly after WWII. When I came into the US Air Force in the mid-1970s, this was still the state of GLOC-prevention training.
In the mid-1980s, the USAF started sending new fighter pilots to centrifuge training. Before long they decided to send experienced fighter pilots as well. It was advertised as a training program, but one with a built-in gotcha. If you experienced GLOC in the ‘fuge, you’d be grounded for a few weeks, during which you’d have to exercise daily to increase your anaerobic strength, then sent to the ‘fuge again. If you failed a second time, your fighter days were over. If you failed egregiously, your flying days might be over. What could be worse than that?
I’ll tell you what’s worse: they videotape you in the ‘fuge. If you GLOC and do a spectacular chicken, every pilot in the USAF will get to see you in a training tape. And they will laugh at you.
I got into the F-15 in 1978, back before mandatory centrifuge training. When the USAF started sending new fighter pilots to the ‘fuge, I was in Alaska serving my second F-15 tour, and had more than 1,000 hours in the aircraft. I was safe. A couple of years later, when they started rounding up experienced pilots for centrifuge training, I was serving a joint staff tour at US Special Operations Command—not flying, so still safe. In 1988 I got a third F-15 assignment, to Kadena Air Base in Japan. I expected to be sent to the ‘fuge during requalification training, but it didn’t happen. After flying for a year at Kadena with no apparent centrifuge threat, I figured I’d slipped between the cracks, and damned if I was going to remind anyone I’d never had the training!
I’ve pulled a lot of Gs, but have blessedly never experienced GLOC. Like all experienced pilots, when my vision started to tunnel I’d ease off on the stick and lower the Gs. As long as I controlled the G-onset rate, I could pull 9 Gs with the best of them.
In the centrifuge, however, you can’t ease off on the stick to reduce Gs, and you can’t control onset rate. Technicians control the ‘fuge, and you get whatever they lay on you. A typical centrifuge training run goes like this: 4 Gs for 15 seconds, 5 Gs for 30 seconds, 6 Gs for 30 seconds, 7 Gs for 15 seconds, 8 Gs for 10 seconds, and 9 Gs for 10 seconds, during which time you have to track a simulated MiG on a head-up display by controlling a stick with your hand. Not only do you pull a lot of Gs in the ‘fuge, you pull a lot of Gs for a long time (you try weighing 1,800 pounds for 10 seconds!), and the onset rate is almost instantaneous. You’d never do anything like this in an actual airplane—if you did, you’d GLOC yourself to death! But in the ‘fuge, you have to do it, and you don’t dare lose consciousness.
So there I was, starting my second year at Kadena, when my commander was summoned to a conference at Pacific Air Forces headquarters in Honolulu. And there, they put up a slide showing every centrifuge-delinquent pilot in PACAF. There were only two: Lt. Col. Paul Woodford and Lt. Col. John B______, both at Kadena. The very next day our embarrassed boss had John and I on a C-12 to Yokota Air Base in Tokyo. The day after that we were at the USAF/Japanese Air Self Defense Force centrifuge at Tachikawa.
I was in my mid-40s and John was, I’ll guess, just turning 40. By fighter pilot standards we were old men. Joining us at Tachikawa for our day of training was a 22-year-old F-16 pilot from Misawa Air Base in northern Japan. John and I decided then and there we weren’t going to take a nap no matter how tough it got or how many Gs they laid on us. Not in front of that punk-ass kid, we weren’t. No effing way.
The way it works is you spend the morning in academics, taking refresher training in effective anti-G straining maneuver techniques. Then you go into the ‘fuge, one at a time, while the pilots waiting their turn watch you on closed circuit TV as you spin through the profile. John went first and did fine. I went second. Damn, it was punishing—probably the hardest physical straining I’ve done in my life—but I didn’t pass out either, and in fact I tracked my MiG better than John did. The kid went last, and GLOC’ed between 7 and 8 Gs. John and I watched him come to and do the chicken. We laughed and laughed.
We had the night off in Tokyo, so John and I went out on the town, exhausted though we were. We took a taxi to a hole in the wall place in the Ginza, where two beers and two plates of gyoza, plus the taxi ride, cost a month’s worth of flight pay. As I reached out for my beer I noticed the underside of my arm covered with little red spots. John held up his arm and he had spots too. Later that night, back in my room at Yokota, I undressed and discovered the same spots all over my butt and down the backs of my legs. The technical name is petechia, but pilots call ’em G-measles—they’re what happens when you pull so many Gs your capillaries rupture.
Am I glad I took my turn in the centrifuge after all? Yes, I guess I am. Would I ever want to do it again? Hell, no!
p.s. About the kid: John and I didn’t think about it as it was happening at Tachikawa, but over beer and gyoza that night realized we’d just watched a young man wash out of fighters. The kid would have had to pass centrifuge training before he ever got to fly an F-16, so for him to be at the ‘fuge with us meant he must have GLOC’ed on a training flight at Misawa and been sent to Tachikawa for evaluation and retraining. May god forgive us for laughing at him earlier in the day … although in the long run, it’s likely the young man would have killed himself in an F-16, so in a way the experience saved his life.
© 2020, Paul Woodford. All rights reserved.