Thursday, February 21, 2008
Dr. G and the G forces


By Dr. Sanjay Gupta
Chief Medical Correspondent

I had one of the most thrilling rides of my life yesterday. I was invited by the Blue Angels to ride along on an $18 million jet for about 90 minutes, flying out of Naval Air Facility El Centro, California. I approach these stories like I approach a med school exam. I studied really hard, and tried to learn everything I could about the physiology of pilots.

As is often the case, though, there is a big difference between reading about something and doing it. Now, in full disclosure, I was very worried about taking this ride. I do get sick in the back of cars, and even a little movement on a boat makes me want to toss my cookies. Things like Dramamine have worked in the past, as has ginger. They do not work, however, when you are traveling at supersonic speed in a high-performance jet. The combination of barrel rolls, quick and violent turns and super high G forces - the force of acceleration or gravity that feels like extreme pressure on your body - is not easily treated with any kind of medication.

Before the ride, the Blue Angels gave me an outstanding briefing on anything and everything about the plane. It has two engines that can each generate 16,000 pounds of thrust - and they did. It can travel 1,200 miles an hour and go as slow as 120 mph. The pilot explained to me that going slow was what made this plane unique. Any plane can go fast, but to be able to "hit the brakes" and suddenly slow down made this F18 Hornet, a special plane. It can fly inverted for quite some time, and I didn't even know planes could really do that. There also was plenty of discussion about a "bonus ride." Yep, that's the ejection seat and it can rocket you high enough in the air that even if you are ejected from the ground, you would land safely with a parachute.

There is no question that it was cool to break the sound barrier, though I didn't hear much when I did. We turned cartwheels in the sky and flew through canyons like I was playing a video game. I learned breathing techniques and exercises that help one combat G forces. Simply tensing your leg muscles and trying to stand up against the 12 point harness will force blood into the upper part of your body, including your heart and brain. Contracting your stomach muscles and saying "hick" loudly also does a good job of keeping that blood where it needs to be. From a medical standpoint, at 4G's, you will start to lose color vision, which is why it is called "graying out"; 4.5 G's and you may lose vision all together. Higher G's and your lungs start to collapse, your esophagus stretches, your stomach drops and blood pools significantly in your legs. It's hard for the human body to take, although my pilot seemed to be enjoying it and joking the whole time, sometimes at my expense.

During my flight, I topped 6 G's - six times the force of gravity. The exercise and breathing techniques that I used in training worked for the most part - except for the one time I think I passed out, only to have Lt. Frank Weisser say, "Hey doc, you awake?" I thought I was. I wasn't. And, yes I completed both P's of my Blue Angel flight. Not only did I Pass out, I did Puke. I guess burritos weren't such a good idea for breakfast.

It was a once-in-a-lifetime experience, and I think I will keep it that way.

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Sanjay-
I am now a civilian radiologist but got a chance for a back seat in an A4 during my Navy time- nowhere near as intense an experience as the Blues gave you I am sure. 4 G's plus "speed jeans" will keep you under the blackout threshhold. I will say though that large ziplock bags are a must... I brought and used mine... Thanks for a nice job on the piece!
Ingrid S.
As a former USAF navigator, I trained in high performance aircraft, and had to pull six Gs. Yes, the breathing exercises and muscle tensing were very helpful. (I never passed out and I never got sick.)

Part of my training included briefings about how to breathe, how to tense muscles, and even included videos of others reacting to G forces. I saw one trainee pass out at two Gs, and another make it all the way to 10 Gs. Very useful instruction, and even shows how much punishment the human body can take.

There are very few times in one's life when one gets to experience significant G forces. Elevators and roller coasters are nothing in comparison.

Doc -- if you want to complete your experience, ask to have ejection seat training. I guarantee you, there's no other experience like it!
Dr. Gupta,

As a former Navy Aerospace Physiologist,I gave naval aviators training on how to do the 'hook' maneuver among other issues, to manage high G flights. I had the opportunity to fly in many aircraft up to 7+ Gs, and got to 9 Gs in the Navy centrifuge (that time I did GLOC). Stomach issues is another whole bag of worms, but definitely burritos or tacos are probably not a good idea before your first aerobatic flight. Having done these hi G flights is one thing, but will interest you more about my own experience is that I was discovered this year to have a very large calcifying MCA aneurysm, which by size and calcification, I either had back when I was pulling those Gs or maybe that's what caused it? If I did have it, I'm really extra lucky to have made it through those flights. Anyway, I had the best neurosurgeon who fixed me (STA-MCA bypass). I don't know if I will ever get to pull Gs again, but it was certainly an experience I'm glad I had, and I'm sure you will always cherish too.- Ken
I remember a story I heard when I was stationed in England in 1984. A friend had been given a ride in an F-111 for earning Airman of the Quarter. He relates the same preflight briefings but his take on the G's was a little different. We were all familiar with some of the pilots and although we knew they were in good shape they didn't look overly strong, being mostly runners. During the flight the friend said he realized these guys were much stronger than he thought. The pilot sitting beside him was routinely flipping switches and taking notes while his passenger was struggling to lift his hand from his lap. He could hardly move and the pilot appeared to feel nothing.
What is the possibility of something like an aneurysm developing over time upon many applications of high G and one not knowing about it until it's too late?
Given the advice to tense leg muscles to help force the blood to the upper body, why not use some variation of anti-shock trousers that are used when needed by emergency medical personnel?

(Perhaps these are the "speed jeans" referenced by another commenter.)

Lastly, you mentioned that generally one begins to lose colour vision at 4G's, but I missed whether or not this happened to you. What was your experience vision-wise?

Thank you!

--Glenn
Why no G suit?
Referred to above as 'speed jeans'?
I live near Pensacola and frequently go watch a Blues practice. We have an opportunity to talk with the pilots after. (I'm a former USAF fighter pilot)

The pilots put on a very 'formal' show, marching out in formation and not carrying flight helmets and parachutes like we always did. These are already in the cockpits.

Last time I was there I asked a young Lt. if his G suit was somehow donned in the cockpit (near impossible in my experience)?

He sheepishly grinned and said "We don't wear 'em"
Hunh?
"You're kidding."
"No sir. I kind of wish we did but then theory is that expansion of the G suit might interfere with precise stick control."
I can not imagine flying high G maneuvers without a G suit.

Sadly, it was only a few weeks later that Lt. Foley was killed when his aircraft crashed. I believe that the investigation concluded that he had become disoriented and possibly blacked out during a high G maneuver.

This happened to me once in pilot training with no G suit. My instructor was flying (T-37) and without warning did a high G turn. I was completely unprepared and blacked out. When I came to my legs were convulsing and I was violently kicking the rudder pedals. Scared the heck out of him AND me. He didn't do that again.

Massey in Alabama
You are so lucky. My Husband would have given almost anything to go on this ride. He so badly wants to go to space. What else do physicists' want to do?
Lucky you!

April in Michigan
Great to see that the flight went as planned! Your performance was respectable among the hundreds that have flown. Well done!

Len "Loni" Anderson
Blue Angels 2002-2004
It's always a pleasure to read about experiences with the technology our world devised. As an employee of GE Aviation, or the company that produces that 16,000 lbf thrust to the F/A 18 hornet, and an avid fan of the U.S. Navy Blue Angels, it's great to see Dr. Gupta give some serious appreciation to our world of aviation.

P.s., it's also nice to see Mr. Anderson's post. I'm a big fan!


-Partha from Blacksburg, VA
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