Runway numbers changing...BACK !!

[Sid Lambert]

Money makes the world go-around.

Maybe it's Jeppesen changing the runways to validate it's database update costs!

[Jimboscr]

The North and South Poles have vary a lot during Earths history. There is an excellent article on NASA's science web page.
Here is the linkhope I did that correctly)
http://science.nasa.gov/science-news...magneticfield/

There is also a science page that is dirctly reffering to the change of rumway numbers:
http://www.livescience.com/9231-eart...ay-change.html

If the link dosen't work here is the jist of the article.

What's going on in Florida?

Travelers have struggled with the complexity of navigating by compass for centuries, and modern American travelers are no exception.

Runways are designated according to the points on a compass, and the drifting magnetic north means that they, periodically, need to be renamed.

"Recently, the drift has caused our runways' orientations to be closer to the next increment on the magnetic compass," Tampa International Airport spokeswoman Brenda Geoghagan told LiveScience in an e-mail.

For example, the west parallel runway, which was named 36Left ?18Right to designate compass points of 360 degrees and 180 degrees, is being renamed to 1Left ? 19Right, to indicate 10 degrees and 190 degrees, since the runway designations are separated into 10-degree increments.

Adjustments to runways like this and to navigational aids are ongoing, according to Kathleen Bergen, a spokeswoman for the Federal Aviation Administration's Southern Region. A third airport is scheduled to rename its runways in October; however, the changes aren't necessary for all airports in the Tampa Bay area, she said.

Every five years, federal agencies tabulate and publish a value called magnetic variation, which varies by location. Similar to declination, it correlates true direction to the magnetic compass readings needed for navigation.

These values are used to update navigational aids, such as instrument landing systems and beacons, she said. If there is a change of more than three degrees at any given airport, then runways need to be renumbered, as is happening at the Florida airports, Bergen said.

While aviation in the United States still relies on ground-based radar, which is calibrated to the local magnetic variation, it is moving toward a satellite-based system.

"Runways are still aligned toward magnetic poles. That?s not going to change," she said.


Jim

[Ron Lee]

Originally Posted by Jimboscr

If there is a change of more than three degrees at any given airport, then runways need to be renumbered, as is happening at the Florida airports, Bergen said.

So 188 degrees to 191 degrees requires a runway change? No doubt it is not just a matter of "three degrees."

I can see 194 degrees to 197 or even 196 degrees.

[Sparky]

This should help you visualize the changing magnetic variation (declination)...



Sorry, the image turned out smaller than I thought. Here's a link to a better image...

http://upload.wikimedia.org/wikipedi...90_to_1990.gif

[Av8torTom]

Originally Posted by kevinh

A runway # change is a 10 degree change ;-)

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[az_gila]

Every five years, federal agencies tabulate and publish a value called magnetic variation, which varies by location. Similar to declination, it correlates true direction to the magnetic compass readings needed for navigation.


...and all of the time I thought the magnetic variation lines printed on the Sectional charts were up to date...

Checked a few old sectionals against the latst and they all refer to the 2010 database.