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I read that very high g forces could kill a pilot, brain pushing into the skull.

Is there a way of decreasing or surviving these forces and how would it work if you ignore aircraft capabilities.

If not what is the maximum survivable g force with current technology.

DeltaLima
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SRawes
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3 Answers3

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I read that very high g forces could kill a pilot, brain pushing into the skull.

High G-Forces cause blood flow to the brain to be impeded due to blood pooling low in the body under high acceleration. This causes the pilot to black out eventually.

Is there a way of decreasing or surviving these forces and how would it work if you ignore aircraft capabilities.

Yes, most if not all modern fighter pilots wear G-Suits. The basic principal of operation is to constrict blood flow to the lower body to prevent pooling in a high G maneuver to increase blood flow to the brain. The g-suit typically buys the pilot about 1G of increased tolerance. The average human tolerance is between 3G and 5G. Aside from possibly some aerobatic planes I dont know of any civilian or commercial aircraft equipped with G-Suits. Generally speaking good heart health can help mitigate the effects in sustained G situations. This why it is so vital that fighter pilots be in top physical shape as fighter planes are capable of very high G maneuvers.

You can decrease the overall G-Force experienced by altering your maneuver (i.e. not undergoing as much acceleration). However in a combat situation some high G maneuvers may be warranted and thus the suits are used. In civilian flying all deliberate maneuvers are well within human limits.

If not what is the maximum survivable g force with current technology.

This depends on the exposure time to the G-Force, see this question/answer.

Community
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Dave
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  • But the is for passing out, what is the max g force or ways of preventing physical injury such as parts of the body inside the body continuing to travel while the outside has stopped? @dave – SRawes Mar 10 '17 at 00:09
  • Its about sustained exposure over time, there is no hard limit. You can take a look at this article for some ranges. If you provide more text to the question like a specific scenario I may be able to provide a better answer. – Dave Mar 10 '17 at 00:24
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    This article, https://en.wikipedia.org/wiki/John_Stapp, makes interesting and relevant reading... – DJohnM Mar 10 '17 at 16:34
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    There is a mismatch between your numbers. “Average human tolerance is 3–5G” and “g-suit typically buys the pilot about 1G” faill to add up to the 9G that fighter pilots sometimes do. – Jan Hudec Mar 10 '17 at 22:21
  • The 3-5G number is for the average human. Most fighter pilots are in far better physical shape than the average person. Heart health, training, and other mitigation techniques can lead to far higher G loads. – Dave Mar 11 '17 at 00:41
  • @Dave, this should then also be mentioned in the text. – Jan Hudec Mar 12 '17 at 22:25
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I read that very high g forces could kill a pilot, brain pushing into the skull.

Not really. Humans who have been killed by very high accelerations (in the order of tens to hundreds of gs for a fraction of a second) tend to look perfectly fine on the outside, but are a mess internally. The most likely cause of death is rupture of the coronary arteries, followed by massive internal bleeding. Think Evelyn McHale (picture below, source):

Evelyn McHale

These brief but very strong decelerations are typical for aviation accidents. Moving over into the survivable range you will again find tens of gs, but they could only be survived with plenty of restraints. Think Dr. John Stapp (picture below, source).

Dr. John Stapp in a deceleration experiment

Now you will argue that you look at accelerations in a different direction. That's my point: There is not a single magic number, but a wide range, depending on several factors:

  • Duration of exposure. Look at Eiband diagrams to get an idea. At 1 second exposure a well-trained sitting human will survive 10g unharmed and will suffer severe injuries above 30g.
  • Direction of exposure. Again, look at Eiband diagrams. In a prone position the same pilot who could only tolerate 10g while sitting will survive 40g for one second.
  • Physical condition: Older and infirm people will tolerate maybe a third of what a young and fit person can suffer through.
  • Technology: Restraints, anti-g suit, anti-g straining maneuver (a physical technique where the aviator pushes air out of the lungs against a closed glottis, while simultaneously contracting the muscles in the calves, thighs, and shoulders).

A combination of all three enables a trained pilot to sustain 9 gs sitting for several seconds. Proof:

video: "I want 30 seconds...!" 9g for 30 seconds! vol.2.
"Centrifuge training for qualifying to Gripen at Sweden" (YouTube)

Additional evidence: When the F8F Bearcat was introduced, Grumman told the pilots not to pull more than 7.5 gs, because at that load the wingtips would come off in order to protect the rest of the wing from overloading. Mysteriously, lots of F-8F returned with their wingtips clipped. Those Navy pilots simply wanted to find out if the protection worked.

When you want to go beyond that, switch to a prone position. That effectively quadruples the limit, on the other hand the straining maneuver will lose most of its effectiveness.

Peter Kämpf
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Interestingly, and not so practical for flying but has been studied by the European Space Agency, if you are immersed in a fluid bath you can withstand extraordinarily high G forces, upwards of 24 Gs.

Old question on Physics Stack: Does Liquid Immersion protect against G forces?

MikeY
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  • filling a g-suit with liquid is a thing too: https://en.wikipedia.org/wiki/G-suit#Red_Bull_Air_Race –  May 10 '22 at 11:32