# How many G's can a pilot endure?



## Freebird (Jan 22, 2009)

I have a question for you pilots out there, who may have had a turn in an accelerator.


I was talking with a friend the other day about spaceflight the effects of long term G's on passengers.


How long is the initial burn on the shuttle, and how many G's is it?

Can a pilot/astronaut take 2 G's for a couple of hours in an acceleration couch?

What about 3 G's? Could you take that for 2 hours?


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## Maestro (Jan 22, 2009)

I think you can only take Gs for a short period of time.

I saw on a show that Harrier pilots had to take up to 5 Gs before passing out in order to be allowed to follow the fighter pilot training.

If you failed that test, you had to go with the helicopter pilot training... Or choose an other career.

A lot of things will influence your result... Your physical shape (is your heart strong enough to pump blood to your brain long enough ?), the distance between your head and your heart (a shorter distance = easier for the heart to pump blood there) and a few other things...


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## Freebird (Jan 25, 2009)

Maestro said:


> I think you can only take Gs for a short period of time.
> 
> I saw on a show that Harrier pilots had to take up to 5 Gs before passing out in order to be allowed to follow the fighter pilot training.
> 
> ...



Thanks Maestro.

How long did they have to withstand 5 G's? Probably only a few minutes?


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## HoHun (Jan 25, 2009)

Hi Freebird,

>How long did they have to withstand 5 G's? Probably only a few minutes?

I believe G tests in centrifuges are usually limited to times measured in seconds rather than in minutes.

Here is a good discussion of transient Gs ... I haven't checked how well it relates to long-term Gs:

"Of + and - G's" part two - alt.games.warbirds

Regards,

Henning (HoHun)


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## Maestro (Jan 25, 2009)

freebird said:


> Thanks Maestro.
> 
> How long did they have to withstand 5 G's? Probably only a few minutes?



Hmmm... I don't know. But it certainly wasn't calculated in minutes. Here is a G-Test video made at 9 Gs... For F-16 pilots.


_View: https://www.youtube.com/watch?v=3rQexWEwV6M_


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## Freebird (Jan 26, 2009)

9 G's is pretty high, even 6 G's is pretty extreme. I was looking at less G's {like 2.5} so if they were in a suit and reclined it might be possible to take it for extended periods {a couple hours for a primary burn}, the effective G's might only be 1.25 or 1.5 with a good suit seat

From HoHuns link



> had to do a couple of profiles without the aid of a G suit, but I did have a G suit on for the 90 second profile. One thing I should mention about G suits. They only add .5 - 1.5 G’s to your G tolerance level (depending on suit fit, pilot physiology, comfort zippers, etc.) I estimate that my suit gives me about a 1G advantage. So, if I am pulling 7.5G, my body only has to work hard enough as if I were pulling 6.5G. That 1G advantage combined with a disciplined AGSM are what keep me awake while pulling a lot of G. Unfortunately, no G suit helps you turn your head to look around when it weighes 100 pounds. That you have to do yourself.


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