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#1
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Magnetic reversal
[The following is for idle speculation and mental recreation.]
A recent issue of Scientific American had an article about the Earth's magnetic field reversals. The article presents some plausible explanations of the reversals that have occurred repeatedly throughout geologic times. It also presents some indications that another reversal is like to happen soon (in terms of geological time-scale "soon"). It was interesting to contemplate the consequences of a reversal on our daily lives. What is ATC going to use for headings? You may be going geographically northward but the compass is reading around 180. Which number do you use to describe what's actually happening? Airways are prescribed on magnetic courses. VOR orientations are aligned to magnetic directions. I imagine that magnetic reversals don't occur overnight, so the transition would be even more chaotic. We'd get a magnetic deviation setting along with the local altimeter setting in clearances? Since the scenario may be a thousand years or more in the future ("tomorrow" on the geologic time-scale), none of us has to worry about it in the next few days. |
#2
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Everett M. Greene wrote:
Since the scenario may be a thousand years or more in the future ("tomorrow" on the geologic time-scale), none of us has to worry about it in the next few days. You didn't read the article clearly. It can take from 4,000 years to 9,000 years for the reversal to be completed. But magnetic headings could become unreliable much more quickly than that. I've started looking into some form of inertial platform for our club aircraft. I figure that we may have as little as 1,000 or 2,000 years, so I'm trying to get this fast-tracked. - Andrew |
#3
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"Everett M. Greene" wrote in message ... [The following is for idle speculation and mental recreation.] A recent issue of Scientific American had an article about the Earth's magnetic field reversals. The article presents some plausible explanations of the reversals that have occurred repeatedly throughout geologic times. It also presents some indications that another reversal is like to happen soon (in terms of geological time-scale "soon"). It was interesting to contemplate the consequences of a reversal on our daily lives. What is ATC going to use for headings? Degrees TRUE. You may be going geographically northward but the compass is reading around 180. Which number do you use to describe what's actually happening? You throw away the compass and buy a cheap GPS. Airways are prescribed on magnetic courses. VOR orientations are aligned to magnetic directions. But they don't have to be. The radials can be realigned to degrees TRUE. I imagine that magnetic reversals don't occur overnight, so the transition would be even more chaotic. We'd get a magnetic deviation setting along with the local altimeter setting in clearances? Maybe a little chaotic for VFR types without a GPS for a short while until they get one. Magnetic navigation would cease to exist. All nav would be done by GPS. All directions will be stated in degrees TRUE. Some repainting of runway numbers required, to match. Complete changeover in one month, tops. |
#4
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Icebound wrote:
Complete changeover in one month, tops. I've trouble believing that KCDW could get through the bidding process to hire the contractors to choose the artists to recommend paint colors for the runways in less than a millenium. - Andrew |
#5
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I'm still trying to figure out what the runway numbers would be if you
built crossing runways with the intersection point at the magnetic North Pole. I guess the runway numbers (magnetic inbound) would be 36, 36, 36, and 36. Now you're telling me that I should plan on naming them 18, 18, 18, and 18? Yikes! Seriously, though, check out the following approach plate and magnetic variation notes at Barrow, AK. They already have magnetic problems up there. http://www.naco.faa.gov/d-tpp/0503/05463I6.PDF JPH Everett M. Greene wrote: [The following is for idle speculation and mental recreation.] A recent issue of Scientific American had an article about the Earth's magnetic field reversals. The article presents some plausible explanations of the reversals that have occurred repeatedly throughout geologic times. It also presents some indications that another reversal is like to happen soon (in terms of geological time-scale "soon"). It was interesting to contemplate the consequences of a reversal on our daily lives. What is ATC going to use for headings? You may be going geographically northward but the compass is reading around 180. Which number do you use to describe what's actually happening? Airways are prescribed on magnetic courses. VOR orientations are aligned to magnetic directions. I imagine that magnetic reversals don't occur overnight, so the transition would be even more chaotic. We'd get a magnetic deviation setting along with the local altimeter setting in clearances? Since the scenario may be a thousand years or more in the future ("tomorrow" on the geologic time-scale), none of us has to worry about it in the next few days. |
#6
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"J Haggerty" wrote in message news:8wn3e.38$KI6.5@okepread07... Seriously, though, check out the following approach plate and magnetic variation notes at Barrow, AK. They already have magnetic problems up there. http://www.naco.faa.gov/d-tpp/0503/05463I6.PDF Nothing new. All of Canadian airspace marked on this map http://webhosts.nunanet.com/~pnagle/ndairspacelg.jpg as "Northern Domestic Airspace" uses TRUE north headings only and no magnetic nav due to unreliability. When operating in this airspace the rules call for the aircraft to be equipped with "a means of establishing direction that is not dependent on a magnetic source" |
#7
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"Icebound" writes:
"Northern Domestic Airspace" uses TRUE north headings only and no magnetic nav due to unreliability. When operating in this airspace the rules call for the aircraft to be equipped with "a means of establishing direction that is not dependent on a magnetic source" What does one use for such a means? |
#8
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Andrew Gideon writes:
Everett M. Greene wrote: Since the scenario may be a thousand years or more in the future ("tomorrow" on the geologic time-scale), none of us has to worry about it in the next few days. You didn't read the article clearly. It can take from 4,000 years to 9,000 years for the reversal to be completed. But magnetic headings could become unreliable much more quickly than that. I've started looking into some form of inertial platform for our club aircraft. I figure that we may have as little as 1,000 or 2,000 years, so I'm trying to get this fast-tracked. Good idea. Mother Nature can be as unpredictable governments. It's never a bad idea to be prepared for the worst-case scenario. [Anybody want to make a wild guess as to when the FCC is going to order termination of all analog TV broadcasting and what the effective date will be? The earliest effective date is 1/1/07 by law but...] |
#9
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"Everett M. Greene" wrote in message ... "Icebound" writes: "Northern Domestic Airspace" uses TRUE north headings only and no magnetic nav due to unreliability. When operating in this airspace the rules call for the aircraft to be equipped with "a means of establishing direction that is not dependent on a magnetic source" What does one use for such a means? GPS, Inertial-Gyro systems, and celestial nav. You take a course such as this: http://people.aero.und.edu/~deremer/courses.html and pay particular attention to Level 3, number 2 :-) : a.. Navigation without magnetic compass: gyro errors, finding & using the sun's true bearing, and finding true north without celestial reference |
#10
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"Icebound" wrote in message
... But they don't have to be. The radials can be realigned to degrees TRUE. Magnetic navigation would cease to exist. All nav would be done by GPS. All directions will be stated in degrees TRUE. Some repainting of runway numbers required, to match. The nice side-effect being that after this change, you'll never have to rename your runways and repaint the numbers due to changes in magnetic variation (as I believe Bourn in Cambridgeshire did a little while ago). :-) D. |
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