Simviation Forums

Curious about g-forces and the human body.
Using a fighter jet for example (pick your fave) I know on take off from a carrier or anywhere else for that matter that your body takes on some major "G's" and the same when making some extreme manuvers.
But the Question is when at a crusing speed (doesn't matter) take mach 1 for example how does the body react to the g-forces?
Does it "adapt" or are the forces constinly affecting the body in some way?
Your body can adjust to temperature, loud noise, and even atmosphereic pressure, but what about sustained g-forces?
Sorry about a odd and matbe cunfusing question, but i'm curious. And since my chances of ever flying in a F16 are slim to none I'll never be able to experiance it.

I'm not quite sure what you're getting at here. Normal flight does not involve great acceleration or G forces. In fact, Michael Schumacher demontrated this recently by beating the EF 2000 Typhoon advanced jet fighter in a "drag race" with his F1 Ferrari. http://cnews.canoe.ca/CNEWS/WeirdNews/2003/12/11/284161-ap.html

Jet fighter pilots wear G-suits (properly named anti-G suits) to overcome the effects of positive G during typically violent manoeuvres. These are like corsets worn around the thighs & lower stomach. They inflate automatically above a certain positive G which helps to prevent blood draining from the upper body (& thus the brain) to delay blackouts. There are also basic excercises an aerobatic pilot without the luxury of a G-suit can do which have the same effect.

if you fly at a constant speed, your acceleration is zero, so according to Newton: F=m.a (force=mass x acceleration). when your a=0, F=0 so no forces. i just came up with this myself, but do you think it's acceptable? no force, no extra G's...

I'm no great shakes at scientific theory or formulae but it sounds logical to me Bones.
The whole point is the accleration or change in relative speeds. If you're travelling straight & level at a constant speed there will be no G forces. Jet aircraft have a surprisingly low acceleration - compared with racing cars for example. I think the average F1 driver experiences more G during a race than a pilot.

Not having experienced it myself I'm not sure about when you hit the A/B button.

hagar, schumi lost to the typhoon 2 out of 3 times.
i'd imagine the feeling of acceleration is like what ya feel in a standard comercial plane, when ya start out ya get pushed into your seat, but once your airborne and speed up, you dont really feel it

hagar, schumi lost to the typhoon 2 out of 3 times.

I'm well aware of that Craig. Read the article from my link.

The fact that he beat it over a short distance is what I was getting at.

i see:)
my bad, i really should spend extra time interpreting these things better when tired:)

hagar, schumi lost to the typhoon 2 out of 3 times.
i'd imagine the feeling of acceleration is like what ya feel in a standard comercial plane, when ya start out ya get pushed into your seat, but once your airborne and speed up, you dont really feel it

This is sort of what I tought. Once at a constent speed your body and plane are moving at the same rate so no differance would be noticed.
But I was wondering the effects ,lets say you start to do a number of barrel rolls at mach 1 (if possible), I would think your guts would all shift because of centrifical force, or am I wrong because once again palne and man are moving at the same rate?
What Bones said does make sense, and if that is true you would only feel effects when making a turn, dive, climb etc, correct?
I guess the best way to find out would be asking a fighter pilot, I know there has to be one here somewhere!!

I'm not quite sure what you're getting at here. Normal flight does not involve great acceleration or G forces. In fact, Michael Schumacher demontrated this recently by beating the EF 2000 Typhoon advanced jet fighter in a "drag race" with his F1 Ferrari. http://cnews.canoe.ca/CNEWS/WeirdNews/2003/12/11/284161-ap.html

Jet fighter pilots wear G-suits (properly named anti-G suits) to overcome the effects of positive G during typically violent manoeuvres. These are like corsets worn around the thighs & lower stomach. They inflate automatically above a certain positive G which helps to prevent blood draining from the upper body (& thus the brain) to delay blackouts. There are also basic excercises an aerobatic pilot without the luxury of a G-suit can do which have the same effect.

But what about the effects on the brain? How is damage prevented there?
If I start sounding like a three year old child let me know and I'll stop!

if i remember rightly Bman used to fly some jet, i might be wrong though

How about in a 747? How powerful are those in that aircraft?

But what about the effects on the brain? How is damage prevented there?
If I start sounding like a three year old child let me know and I'll stop!

The human body is quite remarkable & has its own fail-safe system. Excessive amounts of positive G will drain the blood from the brain causing you to black out & become unconcious. This will prevent brain damage but is obviously dangerous in an aircraft or any other form of transport - hence the anti-G suit to delay the effect & enable the pilot to withstand more G than normal.

All aircraft are stressed to certain positive & negative G factors depending on type. Many high-performance aircraft can far exceed the capabilities of the human body & there are obviously restrictions on that which the pilot should be well aware of. The blackout is gradual & if you see the visual symptoms you immediately ease off the pressure to reduce the G forces.

The amount of G the body can stand will vary with the the person, depending on age, general health, experience & how fit they are. If you do something every day you get used to it. Any professional fighter or aerobatic pilot will know the capabilities of their own body. I believe the latest fly-by-wire systems do this automatically. The aircraft is actually flown by a computer which will not allow the pilot to exceed his/her own body's (or the aircraft's) capabilities.

PS. If you've ever been on a roller-coaster & been pressed down in your seat during the ride you have experienced positive G. In fact this is far more than the average private pilot will ever experience while flying.

The loop & barrel roll are positive G manoeuvres. If performed correctly you could do them quite safely without being strapped in.

PS. If you've ever been on a roller-coaster & been pressed down in your seat during the ride you have experienced positive G. In fact this is far more than the average private pilot will ever experience while flying.

Really? Even in something like a fighter jet?

"if i remember rightly Bman used to fly some jet, i might be wrong though "

He flew F-14s with the USN (lucky &*$

Really? Even in something like a fighter jet?

Although this was a long time ago I had a flight in a RAF Hunter advanced trainer (simply a 2-seat version of the front-line jet fighter) & broke the "sound barrier" twice in an almost vertical dive from 43,000 feet. I wore an anti-G suit which was far more painful than the G effects. Despite doing some reasonably high-G manoeuvres these were done quite smoothly with no violence involved.

Earlier this year I was fortunate enough to have an advanced aerobatic lesson in the Extra I use as my avatar. Although this is a very slow aircraft compared with the Hunter or a modern jet fighter it is far more lively & manoeuvrable. The instructor, himself an ex-member of the RAF Red Arrows, told me it will roll faster than the BAe Hawk (400 degrees per second) & is stressed to something like 26 G, both positive & negative. He assured me that I would break myself long before damaging the aircraft. I could be wrong but seem to recall that aeobatic display pilots regulary cope with + or - 9 G. We had no anti-G suits but I was taught a simple exercise to delay the onset of blackouts due to positive G. I was delighted & even my instructor was impressed when I withstood +5 G (the maximum allowed for my first lesson) with no ill-effects. I have a certificate to prove it. Not bad for an old codger the wrong side of 60.

PS. As for roller-coasters, I read they can often pull up to +6G.

PPS. I checked my facts. http://www.geocities.com/cedarpoint6/forces

PPPS. This is the Hawker Hunter T.7. Very much like the one I had that ride in back in 1959. I can still remember every precious moment as if it were yesterday.