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Why Airports Rename Runways When the Magnetic Poles Move (wired.com)
An anonymous reader shares a report: For decades, pilots heading into or out of Wichita Eisenhower National Airport in southeast Kansas have had three runways to choose from: 1L/19R, 1R/19L, and 14/32. Now, at the orders of the FAA, the airport will spend hundreds of thousands of dollars to give itself a makeover. Workers will repaint those huge numbers at the ends of each runway and replace copious signage. Pilots and air traffic controllers will study new reference manuals and approach plates, all updated to reflect an airport whose three runways have been renamed. World, meet 2L/20R, 2R/20L, and 15/33 -- which happen to be the same runways that have been welcoming planes since 1954.
This is not a "What's in a name?" situation. The runways may be the same sweet-smelling stretches of tarmac they've always been, but the world around them has changed. Well, the magnetic fields around the world have changed. The planet's magnetic poles -- the points that compasses recognize as north and south -- are always wandering about. That's a problem, because most runways are named for their magnetic headings. Take Wichita's 14/32. First off, because planes can land or take off from either direction, you can think of it as two runways: 14 and 32. (Pro tip: Pilots say "one-four" and "three-two," not 14 and 32.) If you're looking at a compass, one end is about 140 degrees off of north, counting clockwise. For simplicity's sake, the headings are rounded to the nearest five, and dropped to two digits. So if you're looking down at Wichita Eisenhower, runway 14/32 is the one running from the northwest to the southeast.
This is not a "What's in a name?" situation. The runways may be the same sweet-smelling stretches of tarmac they've always been, but the world around them has changed. Well, the magnetic fields around the world have changed. The planet's magnetic poles -- the points that compasses recognize as north and south -- are always wandering about. That's a problem, because most runways are named for their magnetic headings. Take Wichita's 14/32. First off, because planes can land or take off from either direction, you can think of it as two runways: 14 and 32. (Pro tip: Pilots say "one-four" and "three-two," not 14 and 32.) If you're looking at a compass, one end is about 140 degrees off of north, counting clockwise. For simplicity's sake, the headings are rounded to the nearest five, and dropped to two digits. So if you're looking down at Wichita Eisenhower, runway 14/32 is the one running from the northwest to the southeast.
The deviation between magnetic and geographic north depends not just on the poleâ(TM)s degree of movement, but also the angle you are away from the pole. In some areas of the US, yes, the movement has been about 10 degrees since the mid 20th century.
E pluribus unum
"You are approved to land on runway Kardashian, lookout for cross traffic from runway Jenner"
If you don't use numbers, that will be the end result.
There are a *lot* of aircraft out there that don't have GPS systems built in, and even if they are, they are subject to failure. Airports are built to be properly usable to the lowest common denominator of available technology, and in an emergency, the lowest common denominator may well be the basic magnetic compass.
Emergencies aside, many aircraft (especially home built's, ultralights, and a lot of other non-commercial aircraft) don't bother with things like GPS.
Z
If you're dealing with only 2 runways, your argument is valid - why update for a minor adjustment.... but as a pilot, I can tell you that it's important when there's more than 2 tangential runways, especially in low visibility and/or in a non-IFR equipped plane.
One runway can be labeled 18 and a tangential runway could be 20. If the pole shifts, requiring 18 to be 19 now, you can get confused and come in on approach for 20, potentially causing an accident or other runway incursion. This is an extreme example, but it's a possibility. The tangential runways are the big issue and are why having accurately numbered runways are so important. The more pilot load you can remove, the safe everyone is. Having to think about and mentally calculate a change can cause a serious diversion of attention during a tense landing situation. Something you *really* don't want to happen.