Mark, your opening paragraphs add little to the debate. All I stated was the limit for oxygen use was not set arbitrarily. The fact is hypoxic effects kick in at much lower levels and tolerances vary with individuals. As you stated, the regulators picked a risk level they were happy with because tests have shown that up to 10,000' the effect of reduced partial pressure is generally negligible. Above 10,000' skill levels and judgment start to deteriorate, getting more pronounced with altitude. You could argue altitudes and exposure times all you like but in the end you cannot change the laws of nature.
Christopher Thorpe -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Newton Sent: Wednesday, 25 August 2004 4:17 PM To: Discussion of issues relating to Soaring in Australia. Subject: Re: [Aus-soaring] Regulation and Policing Christopher H Thorpe wrote: > The establishment of a 10,000' limit is not arbitrary but based on research > on the physiological effects of a reduction in partial pressure of oxygen > with ascent to altitude, taking into account the fact that effects vary > between individuals. Is there something innately physiologically superior about United States citizens which suggests that the same research has resulted in their FL125 + 30 minutes up to FL140 limit? Or perhaps American pilots immediately undergo a lung capacity reduction as soon as they clear customs at Sydney International, with a similar increase in capacity when they get home again. The results of the research you speak of would not have been, "Flight about 10,000' is unsafe." Instead it would have been, "Risk increases by x% at 8000', y% at 10,000', z% at FL120, m% at FL140, p% at FL200. Risk factors are further increased by q% with extended exposure times." The research would have been repeated for each type of risk (e.g., eyesight reduction, alertness, reaction times, problem-solving ability, etc) Then the regulators would have picked a risk level they were happy with and made that the law. Australian regulators obviously picked a round-figure number. I don't know what process US regulators would have gone through to choose their limits, but the fact that they include exposure time in the regs suggests that they've invested a little bit more thought into it, because we ALL know that exposure time is actually very important when determining the degree of incapacitation resulting from hypoxia. In the end, you can't say whether the decisionmaking process which has lead to a rule is flawed or not without knowing what level of risk the regulator finds acceptable. Then you need to understand whether the regulator's notion of acceptable risk matches the acceptable risk thresholds of the people who are actually involved and able to be harmed by the risky behaviour. The fact that the Air Force uses the same rules doesn't make them right, it just means the Air Force has used a similar decisionmaking process in arriving at the level of risk they're prepared to deal with. It's also worth pointing out that the fact that the US uses different numbers doesn't automatically make the US rules correct either. To work that out you'd need a quantitative comparison between accidents resulting at (not above) the legal limits in the US and accidents resulting at the legal limits in Australia. If they're identical within (say) a 95% confidence interval, that would suggest that both sets of rules are equivalent in ensuring that incapacitation doesn't lead to accidents. If we were able to determine that, the next question would be, "Why does one nation have less lenient rules than another nation if the more lenient rules are equally effective at achieving their stated goals?" Sadly, that kind of review process is almost never carried out once a rule has been put into action. Rules are to be written and followed, not questioned and changed. - mark -------------------------------------------------------------------- I tried an internal modem, [EMAIL PROTECTED] but it hurt when I walked. Mark Newton ----- Voice: +61-4-1620-2223 ------------- Fax: +61-8-82231777 ----- _______________________________________________ Aus-soaring mailing list [EMAIL PROTECTED] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list [EMAIL PROTECTED] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
