Re: [Phys-l] Earth's magnetic field

[brian whatcott <betwys1@sbcglobal.net>]

On 1/14/2011 6:52 AM, Anthony Lapinski wrote:
> Saw this article online. Tampa airport had to close because Earth's
> magnetic pole is shifting. Never knew of airports closing because of this.
> Has this happen at other airports?
>
> http://news.yahoo.com/s/yblog_thelookout/20110107/sc_yblog_thelookout/florida-temporarily-closes-runway-due-to-magnetic-pole-shifting&vm=r
It was a matter of historical convenience that runway ends are marked 
with two digits representing the runway's magnetic heading modulo ten, 
and that surface winds were notified in terms of direction FROM and speed.
So if the wind is in the general direction  FROM the north, a pilot 
would prefer to taxi for a runway close to 35, 0 or 01 to minimize cross 
wind effects.
As the Terrestrial magnetic axis drifts the magnetic heading of a runway 
changes with time. At some point, the actual mag heading rounds to a 
different number than the one painted at the runway end.
At this point, the runway is closed while the old number is removed, and 
the new one added.

Brian W