Re:Tampa Airport: Moving magnetic poles forces runway changes
by hugh3 on Friday January 07, 2011 @11:20AM
(#2079939)
This is all fine and dandy until the next geomagnetic reversal, at which point we suddenly find everything 180 degrees out of phase.
Re:Tampa Airport: Moving magnetic poles forces runway changes
by AndrewDucker on Friday January 07, 2011 @11:24AM
(#2079956)
Thankfully, runways are numbered with _both_ numbers. So 18/36 or 9/27. Total reversal would leave the numbers the same...
Re:Tampa Airport: Moving magnetic poles forces runway changes
by yogipatel on Friday January 07, 2011 @01:39PM
(#2080541)
No, they'd still have to be swapped (under the current scheme of runway numbering). If you're landing on runway 18, you know your compass better be reading ~180° (after correction for deviation). Similarly, when taking off from runway 18, your compass should read the same.
You can see just how much the magnetic variation changes around the world in this graphic: http://en.wikipedia.org/wiki/File:Earth_Magnetic_Field_Decli...
Even if we could come up with a safe and reliable way to always have true heading displayed in the cockpit, there remains a very pragmatic reason for keeping runway numbers magnetic rather than true: under the current system, we have to change a few runways every once in a great while; if we switched systems, we would have to change every runway in the whole world all at once. It's not just a simple matter of re-painting the runways: publications have to be changed, notices have to be issued, etc. Changes would cascade out into literally every aspect of the aviation industry.