Re: What's your maximum G-load?

[Happy Dog]

> 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.

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

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

moo

[Cub Driver]

On Thu, 30 Jun 2005 11:52:33 -0400, "Happy Dog"
> wrote:

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

A young pilot in good physical condition ought to tolerate 5 Gs. With
specialized training, as was given to Spitfire pilots in WWII, 9 Gs is
possible.

That's strapped in, of course, and in the case of the Spitfire pilot,
he's grunting and straining for all he's worth.

-- all the best, Dan Ford

email (put Cubdriver in subject line)

Warbird's Forum: www.warbirdforum.com
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[john smith]

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

> Cub Driver wrote:
> A young pilot in good physical condition ought to tolerate 5 Gs. With
> specialized training, as was given to Spitfire pilots in WWII, 9 Gs is
> possible.

Gotta disagree with you Dan.
happydog has it right.
G-tolerance is something you develope, you cannot just strain at the
right time and stay awake.
Back when I was younger and in excellent physical condition, I did
aerobatic training. Sustained or repeated G's will quickly drain you
with each successive maneuver. I never did enough to go to sleep, but
repeated 4-5 G maneuver's caused be to gray out for several seconds (the
instructor was then in control of the aircraft).

[Jay Honeck]

> G-tolerance is something you develope, you cannot just strain at the right
> time and stay awake.
> Back when I was younger and in excellent physical condition, I did
> aerobatic training. Sustained or repeated G's will quickly drain you with
> each successive maneuver. I never did enough to go to sleep, but repeated
> 4-5 G maneuver's caused be to gray out for several seconds (the instructor
> was then in control of the aircraft).

How do pilots like Sean Tucker and Patty Wagstaff sustain G loads for their
entire routine?

I know Tucker "takes a break" half-way through his, doing a long climb out
while he catches his breath (or clears his head), but, still -- they seem to
be under incredibly high Gs for a large portion of their 15 minute routines.

I've only had one aerobatic flight, pulling a maximum of 4 Gs that lasted
maybe ten seconds, and even that was a pretty good workout. I can't
imagine doing that -- and far more -- every few seconds for 15 minutes!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Chris Schmelzer]

In article >,
Cub Driver > wrote:

> On Thu, 30 Jun 2005 11:52:33 -0400, "Happy Dog"
> > wrote:
>
> >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. I think that the cutoff point for the average person (sustained)
> >is around 3.5Gs.
>
> A young pilot in good physical condition ought to tolerate 5 Gs. With
> specialized training, as was given to Spitfire pilots in WWII, 9 Gs is
> possible.
>


Most healthy military pilot sorts (completely healthy and fit) have a
RESTING G tolerance of 4-5G, that is without any muscular contraction or
strain maneuver.

Leg and abdominal muscle straining typically adds another 0.5-1.0G on
top of this resting tolerance, and then adding the G-Strain maneuver
(pushing against a closed glottis to increased intrathoracic pressure)
adds above that.

I recently spun in the centrifuge at Brooks AFB and started to gray out
at around 4.2-4.5, and then had to begin the strain (lightly at first of
course) at around 5.3-5.4 G. I was able to go to just over 9G without
blacking out or G-LOCing which was fun (in hindsight) but it REALLY is a
lot of work.

Tolerance varies widely, with some graying out at 3.5 and some going to
7+G with no strain whatsoever.

Good lower limb and abdominal muscle strength helps peak tolerance, and
good cardiovascular fitness seems to help with repetitive Gs.

-Chris Schmelzer, MD, Captain
Medical Corp, Flight Surgeon
110th Fighter Wing, Michigan ANG

--
Chris Schmelzer, MD
Capt, 110th Fighter Michigan ANG
University of Michigan Hospitals
Ann Arbor, MI

[Happy Dog]

"Michael Ash" > wrote in
> In rec.arts.sf.science > wrote:
>> Douglas Bader lost both legs in a pre-WWII flying accident, and
>> re-enlisted at the start of the war. He claimed he could pull more g's
>> in his Spitfire, 'cause there was no place for the blood to pool!
>
> Not to change the subject, but I'm curious as to how a legless pilot fares
> in combat conditions. Rudder control is pretty essential when flying,
> particularly in powerful propellor-driven planes like WWII-era fighters,
> and normally that's all done with the feet. Did he have something special
> rigged so that he could operate the rudders with his hands?

Wondered about that too. I don't know that you could do a safe takeoff
without rudder in a Spitfire.

moo

[Erik Max Francis]

Chris Schmelzer wrote:

> Good lower limb and abdominal muscle strength helps peak tolerance, and
> good cardiovascular fitness seems to help with repetitive Gs.

I heard a report that women tended to tolerate high gee forces better
than women because they tend to be shorter and have different centers of
gravity. Is that still thought to be the case?

--
Erik Max Francis && && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
Heaven ne'er helps the man who will not act.
-- Sophocles

[Steve Rush]

Happy Dog wrote:

> "Michael Ash" > wrote in
>> In rec.arts.sf.science > wrote:
>>> Douglas Bader lost both legs in a pre-WWII flying accident, and
>>> re-enlisted at the start of the war. He claimed he could pull more g's
>>> in his Spitfire, 'cause there was no place for the blood to pool!
>>
>> Not to change the subject, but I'm curious as to how a legless pilot
>> fares in combat conditions. Rudder control is pretty essential when
>> flying, particularly in powerful propellor-driven planes like WWII-era
>> fighters, and normally that's all done with the feet. Did he have
>> something special rigged so that he could operate the rudders with his
>> hands?
>
> Wondered about that too. I don't know that you could do a safe takeoff
> without rudder in a Spitfire.

Bader lost one leg below the knee and the other just above the knee. With
the prosthetics available, he could control the rudder with his hips.

[Happy Dog]

"Jay Honeck" > wrote in message
news:3abxe.119054$xm3.82811@attbi_s21...
>> G-tolerance is something you develope, you cannot just strain at the
>> right time and stay awake.
>> Back when I was younger and in excellent physical condition, I did
>> aerobatic training. Sustained or repeated G's will quickly drain you with
>> each successive maneuver. I never did enough to go to sleep, but repeated
>> 4-5 G maneuver's caused be to gray out for several seconds (the
>> instructor was then in control of the aircraft).

Grey out is something you learn to tolerate. Although it's flirting with
the edge of G-LOC, it's safe to do once you've learned to predict the onset
of G-LOC and learned your personal limits. When I started training, I once
blacked out, in part, from an improper straining maneuver. The instructor
just let me ride it out. Waking up was like coming out of a dream. It took
over ten seconds from lights out to initiating recovery. G-LOC is not to be
****ed with.
>
> How do pilots like Sean Tucker and Patty Wagstaff sustain G loads for
> their entire routine?

Practice, practice, practice. That, and, as you noted, the routines are
designed to allow breaks in G loads.

moo

[Kyle Boatright]

"Happy Dog" > wrote in message
...
> "Michael Ash" > wrote in
>> In rec.arts.sf.science > wrote:
>>> Douglas Bader lost both legs in a pre-WWII flying accident, and
>>> re-enlisted at the start of the war. He claimed he could pull more g's
>>> in his Spitfire, 'cause there was no place for the blood to pool!
>>
>> Not to change the subject, but I'm curious as to how a legless pilot
>> fares
>> in combat conditions. Rudder control is pretty essential when flying,
>> particularly in powerful propellor-driven planes like WWII-era fighters,
>> and normally that's all done with the feet. Did he have something special
>> rigged so that he could operate the rudders with his hands?
>
> Wondered about that too. I don't know that you could do a safe takeoff
> without rudder in a Spitfire.
>
> moo

Bader had artificial legs. They almost resulted in his death, when one or
both of them got hung when he was trying to escape a crippled Spitfire over
France. He managed to escape the aircraft leaving both (?) of the legs
behind. The Germans found his aircraft wreckage and returned the somewhat
worse for the wear legs to him..

[[email protected]]

Apparently the problem of legs getting jammed while exiting the
Spitfire was a common one. Bader was lucky in that he could just pull
the rip-cord, and leave the legs behind.

Actually, it was even better luck for Bader: he had been told that if
he landed a parachute jump with his no-knee-joint prosthetic attached,
the shock would drive the thing right thru his pelvis (More,
short-term, g-loading!)

[Chris]

"Kyle Boatright" > wrote in message
...
>
> "Happy Dog" > wrote in message
> ...
>> "Michael Ash" > wrote in
>>> In rec.arts.sf.science >
>>> wrote:
>>>> Douglas Bader lost both legs in a pre-WWII flying accident, and
>>>> re-enlisted at the start of the war. He claimed he could pull more g's
>>>> in his Spitfire, 'cause there was no place for the blood to pool!
>>>
>>> Not to change the subject, but I'm curious as to how a legless pilot
>>> fares
>>> in combat conditions. Rudder control is pretty essential when flying,
>>> particularly in powerful propellor-driven planes like WWII-era fighters,
>>> and normally that's all done with the feet. Did he have something
>>> special
>>> rigged so that he could operate the rudders with his hands?
>>
>> Wondered about that too. I don't know that you could do a safe takeoff
>> without rudder in a Spitfire.
>>
>> moo
>
> Bader had artificial legs. They almost resulted in his death, when one or
> both of them got hung when he was trying to escape a crippled Spitfire
> over France. He managed to escape the aircraft leaving both (?) of the
> legs behind. The Germans found his aircraft wreckage and returned the
> somewhat worse for the wear legs to him..

To complete the story, he had replacement legs dropped by the RAF whilst he
was in a POW camp.
Bader was also a persistent escapee, and the Germans took his legs off him
for a while to stop him.

[Happy Dog]

"Chris" > wrote in message
...
>
> "Kyle Boatright" > wrote in message
> ...
>>
>> "Happy Dog" > wrote in message
>> ...
>>> "Michael Ash" > wrote in
>>>> In rec.arts.sf.science >
>>>> wrote:
>>>>> Douglas Bader lost both legs in a pre-WWII flying accident, and
>>>>> re-enlisted at the start of the war. He claimed he could pull more
>>>>> g's
>>>>> in his Spitfire, 'cause there was no place for the blood to pool!
>>>>
>>>> Not to change the subject, but I'm curious as to how a legless pilot
>>>> fares
>>>> in combat conditions. Rudder control is pretty essential when flying,
>>>> particularly in powerful propellor-driven planes like WWII-era
>>>> fighters,
>>>> and normally that's all done with the feet. Did he have something
>>>> special
>>>> rigged so that he could operate the rudders with his hands?
>>>
>>> Wondered about that too. I don't know that you could do a safe takeoff
>>> without rudder in a Spitfire.
>>>
>>> moo
>>
>> Bader had artificial legs. They almost resulted in his death, when one
>> or both of them got hung when he was trying to escape a crippled Spitfire
>> over France. He managed to escape the aircraft leaving both (?) of the
>> legs behind. The Germans found his aircraft wreckage and returned the
>> somewhat worse for the wear legs to him..
>
> To complete the story, he had replacement legs dropped by the RAF whilst
> he was in a POW camp.
> Bader was also a persistent escapee, and the Germans took his legs off him
> for a while to stop him.

Roger that. Without comment.

moo

[[email protected]]

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