A Google search using "Fall-Arrest" search term brings up a wealth of
information from industry and research studies. One study conducted by
Wright Patterson AFB suspended subjects in body harnesses a foot or so off
the ground while the subjects were fully medically instrumented, for heart
rate, BP, etc..
see: http://www.cdc.gov/elcosh/docs/d0500/d000551/d000551.html
The test was terminated at each iteration when subjects mentioned feeling
symptoms deemed by medical doctors as dangerous, or if the physicians
monitoring of vital signs, deemed them to be of a nature to terminate the
test. Most tests were terminated in minutes. One subject lost
consciousness.
Earler in the website with this research data, a case history was recounted
of a worker falling from a rail car, equipped with a designed-for fall
arrest system. Persons on scene communicated with the worker, assuring that
rescue resources had been called. The person responded...Once the fall
happened, the worker was suspended rather high in the air, and 911 response
resources were hailed, and it was realized that the situation demanded
specialists to lower him to the ground.
He became unconscious before rescue resources arrived, and when reached by
rescuers had already died.
It was flat stated at the end of the article that a fall arrest system that
saves the worker suspended off the ground IS A MEDICAL EMERGENCY, requiring
quick response to lower the person in the safety harness to the ground.....
I guess the devil is in the details of the suspension harness design...I
Jumped out of "perfectly good airplanes" for 20 some years, and in some
cases had long rides down in the parachute harness. The harness was built
to order, custom sized to my measurements.
Usually, a 2500 ft opening, was accompanied by a 2-1/2 minute ride down.
Sometimes I went for a high opening (10,000 ft) for a 'cross country'..
really beautiful ride.. 10-15 minutes in the harness, I dont recall
discomfort, but the harness has well designed padding under the 3 snaps
(legs, chest) that held me in the harness, and the webbing was just shy of
3" wide.
In the course of this 'other' hobby, with 'normal' parachute openings, in
the old days of round parachutes, 3-4 Gs were normal opening forces. Time
from ripcord pull to 10 mph, is about 3-4 seconds. The perception of the
opening shock also varied widely depending on your body position at the time
of deployment. Suspension points on the harness were right at your
shouulders. A head low, or (heaven forbid) a vertical head down opening was
quite harder, than the preferred horizontal position depoyment, partly due
to higher speeds head down, and partly due to the pivoting action once
deceleration forces are applied to the shoulder attachments of the harness.
A couple of reserve (second, emergency parachute) rides with FAR faster
openings, I STILL remember, Bring you from about 200 ft per second to 20 ft
per second in about .75 second, and HURT. [not nearly as much as the
alternative] Experts say that reserve openings in the old days were
sometimes 10 G. Today, both main and reserve openings are MUCH Milder with
square parachutes.
By the way, speaking of Gs, I can send out a great video of a guest
passenger in a military jet, losing consciousness 3 times ...in mere seconds
each time, while experiencing Hi (probably 6-8) G maneuvers. I have a wave
file, have to figure out how to post it to the net.
Do the google search....it is great reading...
73, DX, de Pat AA6EG aa6eg@hotmail.com;
Skype: Sparky599
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