Tampa airport runways renumbered due to magnetic north movement

airport runway

(PhysOrg.com) -- The magnetic north pole is slowly moving, and the shift is affecting runways at airports in Tampa, Florida, with the major runway at Tampa International Airport closed until January 13th to allow for the signage to be changed and numeric designators at each end of the runway to be repainted.

The primary runway at the is designated 18R/36L, which means the runway is aligned along 180 degrees from north (that is, due south) when approached from the north and 360 degrees from north when approached from the south. Now the (FAA) has requested the designation be changed to 19R/1L to account for the movement of the magnetic . Similar changes are also taking place at the Peter O. Knight airport in Tampa. Later in the month Tampa International Airport’s east parallel and east-west runways will also be closed to allow their signage to be changed. Over 100 sign panels and 40 signs will need to be changed, along with painted signs on the runways.

The magnetic north pole is always slowly moving and is currently heading towards Russia from its current position in far northern Canada. The magnetic north pole moves by around 64 km (40 miles) a year because of changes within the Earth’s core (unlike the true north pole which moves very slowly due to tectonic plate movements). It has moved from extremes of around 10 degrees east in the late 16th century to 25 degrees west early in the 19th century, and is now at around 3 degrees west. The north and south magnetic poles can also switch places, and this last happened about 780,000 years ago.

According to FAA spokesman Paul Takemoto changes at other airports may not be required because magnetic fields vary from place to place. Takemoto said re-designation is rarely required. Such changes are not that unusual, however, with Stansted Airport in London having to do the same thing in 2009, redesignating its 3,000 meter runway 23/05 as 22/04. Stansted airport officials said they would have to renumber the runway again — in another 56 years or so.

Kathleen Bergen, also from the FAA, said runway designations were based on geomagnetic information, and that aviation uses information on latitude, longitude, and the magnetic poles. She said that the magnetic poles are constantly changing, and movements of more than three degrees can affect runway designations and numbering. In far northern areas, where the relative difference in location between true north and magnetic north has a greater effect, aviators tend to use true north as their reference instead of magnetic north.

Takemoto stressed the changes at the Tampa airports would have absolutely no effect on passenger safety.

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Jan 10, 2011
Why can't they just use the real directions and let the navigators compensate for their own compasses instead of repainting the numbers every time the drift gets too large? If it gets to a point where a plane has no GPS or computers capable of compensating for the compass then the plane is probably in an emergency situation and under the guidance of the tower long before they see the runway, right? Has anyone before these runway closures taken off and gotten confused and spent several hours flying in the wrong direction? I think there is a larger problem here than what is painted on the runway.

Jan 10, 2011
The north and south magnetic poles can also switch places, and this last happened about 780,000 years ago.

So how does the magnetic pole alignment tie up with the pole reversal? Did the core swing around completely, doing a 180 degree movement first and then later on come back another 180 degrees?
If so, how long did that change take and how long did the field stay in that position? I do wish the researchers / reporters wouldn't just make a statement and leave the questions up in the air.

From volcanic lava flows, it would appear the reversal were very rapid, within a matter of weeks, not thousands of years.

Question that does remain on this item is how does magnetic field reversal tie up with magnetic field strength diminishing at such a rapid rate? I don't think it has anything to do with each other and that the field is diminishing in strength independently. And of course it has implications for origin of the earth since it cannot have lasted for 4.5By at this rate.

Jan 10, 2011

Even the most cursory glance around would have answered your questions...

From wikipedia:


A geomagnetic reversal is a change in the orientation of Earth's magnetic field such that the positions of magnetic north and magnetic south become interchanged. These events often involve an extended decline in field strength followed by a rapid recovery after the new orientation has been established...

:end quote

No slivers of evidence to be found here for a young earth, I'm afraid!

Jan 10, 2011
@kevintrs, poles drift as well as flip. You're right that the flips are very rapid reversals of magnetic field. I don't know if the timescale is weeks or couple of years, but all very short geologically.

As for field strength, the field strength has varied considerably since the last reversal. Some times stronger some times weaker. I don't think that anyone's tied field strength to a flip.

Jan 10, 2011
Slow. News. Day.

Repainting runway numbers is not that uncommon as the magnetic north moves. The runway 36R and 36L had actually been aligned to 6.5 degrees north for some time. It should be relabeled runway 01R and 01L instead. Look up KTPA on Airnav.com and take a close look at the FAA's airport diagram...

Jan 10, 2011
Runways being fixed because the Poles change alignment. Hmmm! Deja vu anyone?

Jan 14, 2011
Geographic North is a Magnetic South pole and physicsorg.com should know that. TV getting this screwed up is ok but a physics site should understand that a compass needle that points north is a north pole and north poles are attracted to south. The magnetic south pole is what is moving and it is located in the north..

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