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. The magnetic North Pole (as opposed to the geographic one, which doesn’t move) shifts by as much as 40 miles a year, and is steadily headed from somewhere over Canada toward Russia.
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. The other end is 320 degrees off. For simplicity’s sake, the headings are rounded to the nearest 10, 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 airport’s other runways, 1L/19R and 1R/19L, work the same way: The 1 means one end of the runway is 10 degrees off north, the 19 means the other end is 190 degrees off. They share numbers because they run parallel to one another. That’s why they have letters: The L and R stand for left and right, respectively meaning west and east.
That makes things easy for pilots, especially if they’re newbies at the airport in question. When they get the order to land at runway 20R, they can easily pick it out and make sure they’re properly lined up for touchdown.
But those numbers, painted in the 1950s, are no longer accurate, at least not according to the magnetic navigation tools that commercial aircraft still use. The FAA knows all about those itinerant poles, and regularly evaluates runway designations to make sure they’re still accurate. Things only change when the compass reading shifts a certain amount. Say the pole shifts such that the heading of 258 degrees is actually 259 degrees. That still rounds to 260, and the runway would still be called 26. But if the compass reading goes from 258 to 254, you’re now looking at runway 25.
And so, any given year, it’s likely that at least one or two airports will have to break out the white paint. (Because the runway designations are rounded, it takes a decent amount of movement to trigger a change, and not every airport hits that point at the same time.) In 2013, Oakland International’s runways changed from 27 and 29 to 28 and 30. In 2009, the UK’s Manchester International rechristened 6L/24R as 5L/23R.
So what happens if you don’t bother changing the runway designations because it’s such a headache to repaint everything, change every sign, edit all the documents, and find the money to do it? “The big-picture answer is probably nothing,” says John H. Mott, who runs the Advanced Aviation Analytics Institute for Research at Purdue University and has a commercial pilot’s license. These folks are used to minor deviations, and unless an airport has two runways that have nearly identical orientations, they shouldn’t get overly confused.
But the FAA, which obsesses over safety, doesn’t much like “probably,” and any confusion can lead to potential safety hazards. You might throw off pilots who use the runway alignment as a way to verify the accuracy of their magnetic heading indicator before takeoff, says Doug Moss, a commercial pilot and aviation consultant.
Moreover, you don’t want to make it harder, or more confusing, to use that instrument to verify they’re on the correct runway. Both Moss and Mott point to the 2006 crash of Comair Flight 5191 in Lexington, Kentucky. When the pilots tried to take off from runway 26 instead of the much longer 22, they ran off the end of the tarmac, killing 49 of the 50 people aboard. National Transportation Safety Board investigators concluded that the crew failed to check they were in the right spot.1
When it comes to commercial aviation, anything that reduces the chances of such a terrible mistake is welcome, even if it means a pile of work. So Wichita Eisenhower will break out the paint and call the sign shop, and its pilots will learn to love their new homes, 2L/20R, 2R/20L, and 15/33.
1Story updated at 21:20 on Thursday, April 19 to correctly note the runway from which the Comair flight took off.
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