What’s With Those Numbers Painted on the Runways?
Takeoffs, landings depend on wind direction, weather conditions and the magnetic pull of the Earth's poles
By Noah Moore
Published June 19, 2019
Read Time: 3 mins
Looking out an airplane window, we’ve all seen the big, bold numbers (and sometimes letters) painted in white on the runways. At Pittsburgh International, you’ll see 28-L or 28-R, among others. Though these numbers may sound random, each designates one of the airport’s four runways.
From pilots to ground operators worldwide, taking off and landing a plane requires intense, coordinated communication, including this standardized system of naming runways.
For Jim Polachek, a retired pilot and current Airport Duty Manager, these numbers are part of an elaborate system that takes into account coordinates of the globe, prevailing winds and other weather conditions to ensure safe takeoffs and landings.
The best place to start is to think of a compass which points to the North Pole at 360 degrees, south at 180, east at 90 and west at 270. However, the direction the plane is traveling is key. On a north-south runway, for example, a plane enters at the south end in order take off at the north end. Thus, the south end of the runway is designated 36 for 360 degrees, the usual setting for true north, since that’s the direction the plane is heading.
Likewise, the north end would be designated 18, for 180 degrees, or true south. East and west flip flop from the traditional as well. That means either end of a runway, regardless of its orientation, is 18 digits apart, since they are 180 degrees from each other.
Three of the four runways at PIT are designated 28-10.
“Twenty-eight represents 281.1 degrees magnetic,” Polachek said. “Since three runways are aligned at the same angle, they are further named left, right and center to distinguish.”
The number is rounded to the nearest tenth of a degree, and the third digit is dropped for simplicity, he added.
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