Getting off the ground in an airplane, soaring away in the high skies, all of us get mesmerized by the beautiful cities shrinking underneath. For the pilots, however, the ground of the airport runways carry much more meaning. The airport runways are designated with numbers to aid the pilots in taking off and landing correctly in the right spot.
At large airports, there is not just one runway, so all the parallel runways are given a number and a letter designation to identify the left, right and the center if there are many. The airplanes can land from either direction depending on the weather and the winds.
The runways are marked with two numbers that correspond the to the Earth’s magnetic field. The numbers range from 01 to 36, and each of the numbers matches a compass direction. The first number represents the actual bearing of the compass with the number rounded off to the nearest 10 and the last digit dropped. The difference between the two numbers is always 18 representing the opposite direction of the compass or a change of 180°.
The parallel runways on a large airport may get the same two numbers but the letter designation L, R or C helps identify the correct one for landing.
The shift in the Earth’s magnetic field changes the magnetic north pole of the planet which changes the reading on the compass. The FAA checks for this shift every five years. If the change is significant, the numbers on the runway need to be changed.