Happy Dog wrote:
wrote in message news:
G-LOC= "G force induced loss of consciousness" There's a fairly linear
relationship between time spent at positive Gs and loss of consciousness
for
any individual. (Vector pointing straight down or parallel to the
spine.)

The graphs at the site linked below are far from linear!

At any particular g load.

What is linear there?

As another example, I just realized my kids pull more than 2 G's
every day on the swings (although a sub-second timeframe may not meet
my definition of "sustained" :-).

Five seconds is "sustained".

OK. What happens at timescales significantly above 5s?

Sleep.
http://aeromedical.org/Articles/g-loc.html


What is the baseline in the graph at the site? 0g or 1g? Note that
level flight is 1g, of course.

1G

It is mentioned that G-LOC has happened with as little as 2g. This
would mean 60 degree banking turn. I think even airliners allow more -
like, IIRC, Airbus flight envelope protection extends to 67 degrees.
What is the corresponding +g load?

About 3Gs.

And I suspect that this G-LOC at +3, +4, +2 concern pilots sitting and
staying seated in a pilot seat. Thighs horizontal, buttocks supported,
back somewhat supported (reclining enough not to slump forward or aside
on G-LOC). Right?

At which g would one suffer G-LOC while standing up in an aisle?
Walking along aisle?

At which g can one feel safe to get up suddenly and put a heavy item in
an overhead bin? Go and use a lavatory?

It really depends on the individual. Almost anyone can tolerate 2Gs for a
sustained period but moving about or lifting anything heavy would be
difficult.

Especially climbing a staircase...

I think that the cutoff point for the average person (sustained)
is around 3.5Gs.


What would be the effect of 2g sustained for 5 minutes? Or for 5 hours?
I mean, I suppose circling at 60 degrees bank angle would be somewhat
wasteful of fuel, but the airliners do manage 18-19 hours level flight
nonstop and without tanking...

Over 30 degrees of bank angle is unusual for an airliner. If you're not
used to it, 60 degrees looks and feels like 90.

Indeed. On Airbus, bank angles over 33 degrees require constant
sidestick input - but are allowed. This seems to be about 1,19 g.

As stated, 4g for 5 seconds is a major G-LOC risk for pilots (healthy
and trained young males strapped in somewhat reclining seats). It also
does not accomplish that much of a maneuver: it seems to me that at a
cruise speed of 0,85 M, it only changes the direction by 45 degrees,
and at 2 M only by 20 degrees. A 180 degree turn would require
sustaining 4g for 20 seconds if cruising at 0,85 M and for 45 seconds
if cruising at 2 M.

What would this do to non-strapped-down pasengers, or people who are
actually standing up, or climbing down or up a staircase? Besides
Airbus 380 and those 340 with facilities in the underbelly, narrow and
often spiral staircases are major features of Boeing 747, which does
not have flight envelope protection and therefore should be able to
take steeper turns than Airbus planes. And this includes the planes
like VC-25 and E4-B, which are obviously prime military targets and
therefore likely to be forced to engage in aerobatics to evade hostile
action. Also, they are meant for middle-aged to elderly persons. I
wonder at which g-load they can scramble upstairs to the communication
room on VC/25...

Can one sleep (and get up again) at 2g?

That's an interesting question. xposted for an answer.

moo