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>Snip from Patrick
Barfield
<As oher people have pointed out, I wouldn't like
to be sharing a thermal/wave with this person
And nor would I! Indeed this is exactly the thought that
triggered my initial post on the subject. Nice to have the thread brought
back to the key issue so expertly.
Can anyone provide information as to the effect of hypoxia on
peripheral vision?
--
Brian Wade
Personal Computer Concepts
Control SPAM with MailWasher Pro
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----- Original Message -----
Sent: Tuesday, August 24, 2004 11:30
PM
Subject: [Aus-soaring] Oxygen safety
issues
Quoting Terry Neumann <[EMAIL PROTECTED]>:
>
> Finally,
I can't remember any (perhaps I've been above 9999 feet too
> often),
but can someone enlighten me as to just how many accidents or
>
fatalities in gliding in Australia have resulted from people going above
> 10,000 feet without oxygen, or alternatively daring to enter the
> statutory (and essentially un-measurable) glider free zone which
> currently exists in respect of each and every cloud?
>
> Stirring mode < OFF>
>
> Regards,
> Terry
:-)
> (Past policemen and "enforcer" of gliding rules at various
competitions
> since 1971)
>
I'm not going to weigh in to
the policing debate but I do have a few points on high altitude flight safety
that some
people seem to have missed by focusing on the policing
aspect.
The greatest danger about hypoxia is the insidious onset which
means that a pilot can be incapacitated suddenly
without any warning.
Therefore I emphatically disagree with a previous poster who said "if you feel
bad, go
down" because you may not realise that you are feeling bad until
it is too late by which time you could be
unconscious. In fact, one of the
symptoms of hypoxia can be a feeling of euphoria which will delude the pilot
into
thinking that everything is fine until he/she passes the time of
useful consciousness and is unable to fly the
aircraft.
For those
who say "that couldn't happen to me" consider these examples:
I have
done at least 8 hypobaric chamber runs to experience the symptoms and effects
of hypoxia and usually
on each run one indivual out of a group of 8
subjects becomes so incapacitated that they require assistance to
replace
their oxygen mask despite extensive prior briefing that everybody must go back
on oxygen while they
are still able. If somebody can't even replace their
own oxygen mask, how well would they be able to fly an
aircraft?
While I am unaware of hypoxia fatalities in gliders I
remember a Southern Cross Gliding Club Camp in Forbes
about 25 years ago
where one pilot chasing gold height was "off with the fairies" when talking on
the radio. Either
through good luck or good management he descended to a
lower altitude and landed succesfully but afterwards
he couldn't recall
the bizarre things that he had been saying on the radio.
There have
been instances of fatalities in the power world and the only similarity
between the two fields that I
want to highlight is that the pilot's
physiology is the same. So, if these power pilots were unable to recognise
that
they were hypoxic and take corrective action, would a glider pilot
fare any better?
I had the unfortunate duty to preside over a RAAF
board of enquiry for the loss of a Hornet where the pilot
became hypoxic
without being aware of his symptoms (and he had been trained in a hypobaric
chamber). He
subsequently lost consciousness and crashed with his
aircraft.
The King air crash in Sep 2000 (See http://www.atsb.gov.au/atsb/media/mrel019.cfm)
was also caused by pilot
incapacitation due to hypoxia. If he knew that he
was hypoxic, why didn't he go on oxy or descend?
So why haven't we had
any fatalities in gliders if so many people are flying above 10,000? I would
hazard a
guess that pilots have been affected to varying degrees but
either weren't aware of this or didn't want to admit
that they'd violated
a rule. To some degree, the problem in a glider is self-correcting ie if a
pilot is being
incapacitated by hypoxia his flying skills would
deteriorate to such a point that he would lose the thermal/wave
and then
descend to thicker air and recover. As oher people have pointed out, I
wouldn't like to be sharing a
thermal/wave with this person. Also, if
somebody does "take a nap" for a minute, what would happen to the
glider?
Try a simple experiment and let go of the stick for a few minutes if you dare
to see what might happen.
Remember at 10,000 AMSL, the TAS is 20% higher
than the IAS and VNE/manouvering speeds are calculated on
TAS which means
that you are closer to the edge of the flight envelope.
So to sum up,
there are plenty of traps for pilots when flying high without oxygen. The grey
area starts when you
have to apply a rule that covers everybody because
everybody's physiology is different and I have seen some
individuals last
twice as long as others in the hypobaric chamber. I relate it to setting speed
limits on the road.
There are some drivers who can drive safely at 150
km/h on the freeway and I have seen other drivers who
shouldn't be allowed
to drive on the freeway at all. The big can of worms is where you set the
limit and how you
police this limit. Australia has chosen 10,000' as the
limit, the US uses 10,000, yet they allow up to 30 minutes
without oxy up
to 12,000' (See http://www.risingup.com/fars/info/part135-89-FAR.shtml).
That's
my 2c worth and I will continue to monitor the spirited discussion with
interest.
Patrick
Barfield
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