Pulling G's

[BigglesSA]

What’s the worse you have experienced? Is it this BAD?

Pulling G's.png

[thelsa]

Not a pilot myself. In 1976 I flew from Mpacha to Grootfontein in a C130 with the famous Cmdt Tinky Jones. We were just 3 pax and after he taxied out we took off. I was reading a Readers Digest to kill the time. After take-off the procedure was to stay tree-top height to avoid rocket attacks from across the river (Angola) Tinky decided if the rocket wants to get me..... it better come and fetch me.
He climbed at a very stee;p attack angle. My eyes blurred, my face became numb, the letters in the book was blurring and I could not move at all. IMy cheecks felt if someone was pulling them down. It was the most strange experience I ever had. I thought : 'hell this must look good from the outside" I tried to get up to have a peek through one of those small high located windows but could not move my arms to unfasten my seat belt. I tried to get up but was 'glued' to my seat. At about 15000-20000' (I think) he levelled out. I was almost against the roof !
Even that it was scary at that stage, it was the most amazing experiences I've had in my life. Wish I could experience it again

[StressMerchant]

What’s the worse you have experienced?

Umm I guess it was waking up and wondering where the duvet had gone, and wondering why the flying dream was intruding into the real world.

[Sideslip]

Flew the Aviat Eagle 2 with Noel Otten last week.

+5g - 2g

First few manoeuvres were uncomfortable but started relaxing more as the flight continued.

[BigglesSA]

Flew the Aviat Eagle 2 with Noel Otten last week.

+5g - 2g

First few manoeuvres were uncomfortable but started relaxing more as the flight continued.

Did you enjoy it or is it to "uncomfortable"?

Is there a lot of G involved in a spin?

[HairyDog]

Spin is a 1g manoeuvre. Most I've done is +6.5 and -4 in a Yak 52.

Negative g takes a bit of getting used to.

[Lood]

I don't know how many we pulled, but maybe the guys with experience could give an indication:
Firstly, I couldn't move my camera from my lap, nevermind lift it to window height to take a pic and secondly, I had to take a breath and kind of push while holding it to prevent things going blurry or even blackish
Please don't ask what a/c we were flying in - all I can say: NEVER AGAIN

[Sideslip]

Flew the Aviat Eagle 2 with Noel Otten last week.

+5g - 2g

First few manoeuvres were uncomfortable but started relaxing more as the flight continued.

Did you enjoy it or is it to "uncomfortable"?

Is there a lot of G involved in a spin?

I enjoyed it very much.

I used to pax in aerobatic flights on a regular bases when I was much younger so I knew kind of what to expect. I just haven’t pulled that much G in a long time. (And I weigh a lot more now than I did back then )

It only took a manoeuvre or 2 to get back into it.

Spins are not high G manoeuvres. A little (tiny) negative G on entry possibly and a bit of + on the pull out (depending on the pilots enthusiasm) but while in the spin you probably don’t feel much G at all if any.

[noelotten]

I don't know how many we pulled, but maybe the guys with experience could give an indication:
Firstly, I couldn't move my camera from my lap, nevermind lift it to window height to take a pic and secondly, I had to take a breath and kind of push while holding it to prevent things going blurry or even blackish Please don't ask what a/c we were flying in - all I can say: NEVER AGAIN

Pity about that! Aerobatics in general and unusual attidutes in particular are not things an intelligent pilot will subject his passengers to even if they are themselves "flying types" without an introductory talk and, once in the air, a gentle introduction to the experience. It is not to everyone's taste! And here I include people who fly themselves. I have had my share of cleaning out cockpits. Having said that, I do believe that some exposure and training in aerobatics will serve you very well in your aviation career. One learns not to fear unusual attitudes, but to take them in your stride and deal with them in the appropriate manner, without pulling the wings off.

Generally, it is not the amount of "g" that is uncomfortable, but rather the "duration" of the experience. One can pull 10g for 1/2 a second and hardly notice it. The aircraft will certainly know all about it, but the averagely fit person can withstand that level of "g" for a very short period. However, pull 2g for 30 seconds and you will black out!

One has to condition oneself to withstand "g" forces! It is not a "natural" thing that some have and others don't. Anyone who tells you he has never had a "g" tolerance limit is a liar! One "builds up" a "g" tolerance level through practice and conditioning. It is a very intricate subject and I am not qualified to give a definitive treatise on the subject, but in "layman's" terms, one "blacks out" when too much blood drains from the brain, starving it of oxygen. There are various stages of the "black-out" process. With the onset of positive "g" one experiences the following sensations:-

1) First stage:- The limbs, (arms and legs), begin to feel heavy and are difficult to move freely. The cheeks sag and the eyelids droop. The head feels as if it is being pushed into your chest. You feel a weight on your chest and stomach. This is the effect of the centrifigal forces acting on your body. Your eyesight is affected almost immediately ... you get "tunnel vision". You can see reasonably clearly, but you are looking through a long tube. As more blood drains from the head, the tunnel closes down.

2) Second stage- If the "g" loading is maintained, a "grey-out" is on the way! You may still see images, usually very blurred, but there is no colour discernible. Everything is "grey" in colour! This is your warning signal! Take heed and react accordingly and quickly! Reduce the "g" load immediately. From this point onwards, you can slip into deeper stages of "black-out" very quickly.
Important Note ..... The "g" forces do not have to be increased to get to this stage ... only maintained. I have not stipulated a "g" load to achieve this! It can in fact be quite low, 1,5 - 2 "g"s is sufficient to induce this stage if the duration of the "g" loading is sufficiently long. You still feel all the other sensations described above, except now you can see nothing at all. You are still “compos mentis”, i.e. thinking and reasoning, but with difficulty.

3) Third stage:- "Black-out"! All images disappear completely. You turn your head, but see nothing! Surprisingly, you are still able to feel the forces acting on you, and, you are still able to hear sounds.

4) Fourth stage:- Total Hearing loss! Everything goes eerily quiet! You are in state of unconsciousness! You are not “compos mentis!” You need luck on your side to get out of this .... so don’t get yourself into this situation or condition! Some people may even hear the sound of beautiful music and “angelic singing”. Get out of the situation quickly, for those are angels singing!!!

There are a number of factors which influence your "g threshold". In no particular order the following factors come into the general equation:-
1) Fitness level! Fit people have a higher "g" threshold.
2) Heart condition! If you suffer from high or low blood pressure ..... don't do aerobatics .... period! Likewise if you have a headache or a head cold! Very dangerous indeed.
3) Age! The above factors not withstanding, older people who suffer from hardening of the arteries tend to have a built-in resistance to "blacking out". The blood doesn’t course through their veins very quickly. They have a “built-in” “g” suit. But don’t count on it!
4) Tiredness! Lack of sleep is a "No-no!" if you do aerobatics.
5) High ambient temperatures can lower your “g” tolerance. One tends to drink lots of water and that will cause your blood sugar levels to drop, not to mention the SG of your blood. Thin blood = Low “g” tolerance.
6) Contrary to the old wives tales, an empty stomach is not good for your “g” threshold. Give your stomach something to work on if you are going to do aerobatics. Nothing too fatty, but something with some “bulk”. I found a small meat pie or a “boerie roll” to be the best, 30 minutes or so before flying. Keep the blood sugar levels “up”. Energy bars are good! Certain fruits such as bananas are very good. I used to also drink full-cream milk and munch on some "hard" cheese, e.g. Cheddar or Gouda.

I found that the easiest way to keep in shape was to cycle and play badminton. High cardiovascular activities and good stomach and leg muscle conditioners. Hence my interest in cycling!

Negative "g" is another story alltogether! Similar, but appreciably different. That's for next time!

Hope this helps to take the fear out of "Pulling "G"!
Noel Otten

[HairyDog]

Generally, it is not the amount of "g" that is uncomfortable, but rather the "duration" of the experience. One can pull 10g for 1/2 a second and hardly notice it. The aircraft will certainly know all about it, but the averagely fit person can withstand that level of "g" for a very short period. However, pull 2g for 30 seconds and you will black out!

Sorry, but this is very misleading. 10g for any duration and you'll be acutely aware of it! A 100kg man weighs one tonne at 10g. If you're not ready for it that 1/2 second may be enough to remove what's left of you lunch after you've digested it! If you jump off a 5 or so metre (I'm guessing, but something like that) wall you'll probably experience something of the order of 10g, for a very small fraction of a second, when you hit the ground. You can't call that "hardly noticeable".

In a balanced 60 degree turn you are experiencing 2g. So we'd all black out doing our PPL test after 30 seconds of this? Nope.

Duration is a factor and the nett result does depend on both g and duration but these examples are incorrect.

[noelotten]

Sorry, but this is very misleading. 10g for any duration and you'll be acutely aware of it! A 100kg man weighs one tonne at 10g. If you're not ready for it that 1/2 second may be enough to remove what's left of you lunch after you've digested it! If you jump off a 5 or so metre (I'm guessing, but something like that) wall you'll probably experience something of the order of 10g, for a very small fraction of a second, when you hit the ground. You can't call that "hardly noticeable".

I prefaced my statement by saying that it was not a definitive article on "the effects of "g" and blacking out". There are dozens of books on the subject. And I am certainly not wishing to mis-lead anybody! The questions asked were mainly about "what it feels like to pull "g"?"

I was discussing "g" tolerance and what are the stages of "Black-out"; not what causes them!

Pulling 10g by jumping off a wall is not likely to cause you to regurgitate your lunch! You may break your leg, but your lunch will stay put unless you have an allergic reaction to the aneasthetic you're given at the hospital. Pulling 10g in an aircraft for a very short period of time, (1/2, 1 or 2 secs let's say) will have the same effect on your stomach. Of course you will feel it! And the aircraft will register the load ... permanently! You will feel the compression from the centrifugal force,(positive "g"); or from the centrepetal force,(negative "g"); but the blood in your head will not have time to drain into your toes, so it is unlikely that you will "black out" if you are in reasonably good physical condition; (I also made several references to the "duration" factor in my article).

What causes the nauesea and the feeling of sickness is mainly due to spatial dis-orientation, movement of the fluids in the ear and so on! I am not going to discuss what happens there.

If you want to find out how you will react to a session of aerobatics without leaving the ground, take a roller-coaster ride. You will pull 3 - 4 "g" for relatively short periods and even 0 or (-) 1 g as well. What makes most people really sick on the roller coaster is the lateral or "side-ways" acceleration or jolting that disturbs your sense of balance. If the roller coaster is well maintained and the ride is smooth, very few people suffer nauesea. If the rails of the coaster are mis-aligned and people get knocked about laterally ... plenty of green faces! Personally, I hate roller coasters! I am not in control of the situation!

Most people who are not used to aerobatics can easily tolerate several, well executed "barrel-rolls". A reasonable amount of positive "g", 3 to 4, and provided the "ball is kept in the middle", they feel little or no ill effects. Do one "snap roll" or a poorly executed manoeuvre, (head being flung from side to side), and you will be cleaning the aerie for sure regardless of the amount of "g" you pull!

Noel Otten

[nugpot]

As the previous posters have said, there is a big distinction between sustained and instantaneous (snap) g. Instantaneous g can be tolerated at very high levels by the human body without blacking out, because the blackout is caused by lack of blood to the brain, and with snap g, there is no time for the blood to drain from the brain. I stayed fully conscious through an ejection, which initiates with a 19 - 23 g acceleration.

High sustained g will rapidly cause loss of consciousness in anyone not trained to deal with it. Fighter pilots use a g-suit with air inflated bladders to help keep the blood away from the extremities, but even then you have to use high-g breathing and tense all your muscles to avoid g-induced loss of consciousness (G-LOC).

We used to use a very high g defensive maneuver in my previous life on noddy jets called a defensive spiral. If you were attacked by a superior fighter aircraft at altitude, you would drop the nose to about 45 degrees below the horizon and sustain a 6 - 6.5 g turn to low level. This would mean sustaining 6 g for up to a few minutes, which is exceedingly difficult. First signs of the approach of G-LOC is a gray out, where you only see in black and white (gray). This is caused by a lack of blood to the eyes, which first puts the cones (colour receptors in the eyes) out of action. If you do not reduce g or further tense your muscles, the next step will be a black-out, where you are still conscious, but can't see. This is when the rods (monochrome receptors in eyes) are also incapacitated. Very shortly thereafter (if you sustain the g), you will lose consciousness and this might not return for up to 30 secs - usually fatal if at low level or in a fight.

For those of you wondering about how to judge g - most GA and commercial aircraft are cleared to about 2 - 2.5g. A steep turn will result in about 1.5g. Doing aero's in a Harvard or Yak would normally only require 3 - 4g pull-outs for any vertical maneuvers. This would be quite enough to cause gray- or black-outs to anyone not tensing up or not expecting the onset of the g. High performance aerobatic aircraft can normally pull very high g, but most maneuvers only require high g for very short periods and cannot be called sustained high g maneuvers.

A comfortable loop would require about 3 g at the bottom, reducing to 1 g at the top and increasing to 3 g at the bottom. If you lose your pen in a Harvard, you would try and sustain -0.1 g for a few moments and it will float up to where you can catch it.

Negative g is very uncomfortable and needs a completely different tactic to sustain. It will cause serious head-aches if sustained and will probably burst some blood vessels in your eyes. You can easily see from the bloodshot eyes that a pilot has had to sustain high negative g for a while, as in an outside loop (looping towards the undercarriage, instead of towards the canopy).

Hope this helps.

[BigglesSA]

Hope this helps to take the fear out of "Pulling "G"!
Noel Otten[/quote]

"G"eeeesh what a post, very informative

Thanks Noel

[fisherw]

Civilian in the back seat of an F18

http://alt.coxnewsweb.com/ajc/swf/bluea ... angels.swf

Entertaining display of the effect of g's on someone not conditioned for it

[Etiennevaneeden]

Hi there all,

What Noel Otten refers to is exactly as it is...

I was very fortunate to fly almost 1000 hours in the SAAF on Impalas and he is acurate... Miss that

Not too big a deal in any case - If anyone ever has the opportunity TAKE IT...