[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.

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

"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.

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

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.

"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"

"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?

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...]

"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

"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.

Icebound wrote::

>
> a.. Navigation without magnetic compass: gyro errors, finding & using the
> sun's true bearing, and finding true north without celestial reference.

What about FMS and IRUs? Been around on the more sophisticated airliners
since the 767 came out in 1982 or so.

writes:
> Icebound wrote::
> >
> > a.. Navigation without magnetic compass: gyro errors, finding & using the
> > sun's true bearing, and finding true north without celestial reference.
>
> What about FMS and IRUs? Been around on the more sophisticated airliners
> since the 767 came out in 1982 or so.

There are all sorts of things for the big boys, but what
do the small planes use?

What was used for small planes in the days before GPS?

I would think it would be a real challenge to fly the
Alaskan North Slope on a cloudy day (or night) without
at least GPS.

"Everett M. Greene" wrote:

> writes:
> > Icebound wrote::
> > >
> > > a.. Navigation without magnetic compass: gyro errors, finding & using the
> > > sun's true bearing, and finding true north without celestial reference.
> >
> > What about FMS and IRUs? Been around on the more sophisticated airliners
> > since the 767 came out in 1982 or so.
>
> There are all sorts of things for the big boys, but what
> do the small planes use?

The question was asked in the general context of aviation, not just light
aircraft operations.