G-loadings possible before "problems" arise in drivers?

CART had this problem at Texas back in '01...

http://en.wikipedia.org/wiki/Firestone_Firehawk_600

 

I don't know about lateral Gs, but 5 Gs for 15 seconds vertically isn't a problem for most people.

Lateral Gs might be a whole different story, though.

 

Short story

Lateral G (Gy) is a different animal pathophysiologically than 'airplane' G (Gx).

G loss of consciousness (G-LOC) associated with high G maneuvers in the lift vector is from the inability of the heart to maintain perfusion pressure to the brain as the accerative forces require more pressure to push the blood up and through the brain. G-LOC is typically transient and one "wakes up quickly when perfusion is restored, although a bit disoriented and may be doing the funky chicken - mild seizure shakes due to reperfusion.

Lateral G is actually more dangerous for the body in terms of risk for permanent damage. Since the heart and brain are accellerating in the same plane, G-LOC is not typically a factor in lateral G. However, swinging movement of the mediastinal compartment (heart/great vessels) can be dangerous.

I can talk about this for an hour or so if interested.

 

Do high G's in the gravity vector damage the brain?

 

I wonder how those Gs take a toll on the vascular system of the brain...when the blood all of a sudden feels 5x heavier to the vessels, could definitely weaken them (like hypertension).

Did this guy have his aneurysm form as a result of high Gs over his career?

http://www.ncbi.nlm.nih.gov/pubmed/15497373

 

cant beat gravity.

wins every time.

 

High Gz loading will cause what is called a stagnant hypoxia, or hypoxia due to no/low flow to the brain. This is as we said due to the hearts/circulatory system inability to maintain enough pressure to send the blood UP into the head (against the increased force of accelleration). Many people like the metaphor of the sitting body as a standing column of water, and the heart as a pump somewhere in the middle. Under G, the effect is the same as the heart having to push the blood higher. There are also circulatory system compensating mechanisms as well, such as vasoconstriction, increase in heart rate, and so on to increase pressure and flow. Brief exposure to this to stagnant hypoxia may result in just a brief loss of consciousness that clears rapidly when circulation returns as G loading comes off. As you may expect, prolonged no/low flow to the brain may result in damage, but in aviation up until now, we have not seen these extended periods of G-LOC.

Another issue G-onset rate. If Gs are added on more slowly, this gives the body's normal circulatory reflexes to kick in (as well as anti-g straining manuevers (AGSM) on the part of the pilot) and the pilot does better with the higher G acceleration. We lost A LOT of F-16s when they first came out (and still lose a few now) because the computer would let you pull an INSTANTANEOUS 9 gs. Well, that just is instant G-LOC for a lot of people as that even beats the G-suit inflation. A more controlled G-onset, with beginning of AGSM prior, allows higher G tolerance.

I think it is probably intuitive that dehydration and level of anerobic fitness both play a HUGE part in individual G tolerance. Flying in general, and the high g environment in particular, is an isometric anaerobic exercise. And, even as much as a 3% dehydration can cause a 35% decrease in anaerobic capacity.

Resting g tolerance in most folks is about 4 - 5 g's prior to onset of visual loss (due to lowering blood flow to the retina). Most air combat is around 7 G's, and can be up around 9 if you have screwed up and have someone on your tail and your plane can do it. The USAF centrifuge requirement for F-16 pilots, the most brutal out there as of a few years ago, culminated in a 9 G pull for 15 seconds. I personally had to pass this as I was assigned to an F-16 Wing and flew with them, and let me tell you feel beat to hell when it is over and want to just go home and crash.

A "G-suit", most commonly are rubber bladders around the lower extremities and abdomen that fill with air under G. This prevents pooling of blood and fluids in the lower half of the body and keeps it available for the rest (i.e. brain). This is good for one or two g increase in tolerance, as is the AGSM. There are some new whiz-bang anti-g things, but that is for later.


So, anaerobic conditioning, good hydration, moderate g onset rate and good AGSM and you will do fine.

So Rob, is this good enough to be a consultant yet?
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Russ- I asked and Rob said he was not making any new consultants. Of course, that may just have been a story he told me....

You should explain to everyone the difference in training required for high g vs normal folks with regard to heart rate, blood pressure, etc. I have muddled through it before, but better coming from a flight doc. Anaerobic vs aerobic, etc.

Taz
Terry Phillips

 

I'm interested