What do numbers on the runway mean?

Image from : - Flickr

Have you ever noticed big numbers on the runway? If not, then just open google maps and turn on satellite mode and search for the airport near your city and check out the ends of the runway, you will notice those big numbers on them. Those numbers have significant meaning. Let's find out the meaning of these numbers.

These numbers on the runways are used to name them, so that, if multiple runways are available on same the airport then ATC (Air Traffic Control Tower) can mention runway name and tell the pilot  which runway to land on.

Numbers on the runways are based on the magnetic azimuth in which they are heading. North heading is taken as reference. Those numbers are known as QFU codes. So East is 090°, South is 180°, West is 270° and North is 360°. While naming runways, first two digits of the angle of inclination of the runway with magnetic north are taken. So a runway numbered 09 points east (090°), a runway numbered 18 is south (180°), a runway numbered 27 points west (270°) and a runway numbered 36 points to the north (360° rather than 0°).

Compass - Wikimedia

Now if a runway is heading 150° to north then it will be numbered as 15. Similarly if a runway is heading 310° to the north then, it will be numbered as 31.

As each runway has two ends, it has two headings. Every runway has two numbers. The two headings of the runway differ by 180°. So if one end of the runway has a heading of 150° to the north then that end will be numbered as 15 as mentioned earlier. Heading of the other runway will differ by 180°. So heading of that runway will be 150+180 = 330°. Hence, the number on other end of the runway will be 33.

Now suppose the runway has a heading of any random degrees say 144°. Then such number will be rounded off to nearest ten. So in this case for 144° runway will be rounded off to 140° and numbered as 14. Now suppose a runway has an heading of 316°. Guess what will be the number on the runway?
You guessed it right! It will be 32 as 316° will be rounded off to 320°.

Now there is one more possibility, what if there are multiple runways parallel to each other. As runways are parallel to each other their heading will be same. Now how will you number them. In this case location of the runway on that airport is considered. Suppose if there are two runways then the runway located at the right side of the heading will be numbered with the prefix 'R'. R here stands for right. Such as 27R, 32R, 18R, etc. Similarly runway located at left side of the aircraft heading will be numbered with L as a prefix, which stands for left. Such as 27L, 32L, 18L, etc.

John F. Kennedy International Airport Left Runway - Google Maps

John F. Kennedy International Airport Right Runway - Google Maps

Now suppose there are three parallel runways then runways will be located as right, center and left. Right and left runways will be numbered as mentioned above and for the runway in between these two, it will be prefixed with (you guessed it) 'C', which stands for right. Such as 27C, 32C, 18C, etc.

Chicago O'Hare International Airport Center Runway - Google Maps

Hope now you understood those mysterious big number that you've noticed while travelling on an airplane.