Runway Headings: How to Read Them and How To Use Them
Being able to read and understand runway headings is a fairly simple endeavor (that is sometimes skipped over), and it’s also a useful tool for orienting yourself at the airport. So, let’s begin:
Since I enjoy historical connections, we shall take a two paragraph trip down memory lane. If you don’t love history, skip it.
In the early 20th century, the first airports/airfields (College Park Airport, MD claims to be the first airport in the USA) were simple grass strips with a few hangars. As time went on a few airports began having cinder, or gravel, strips, but until about the time of World War II, the majority had grass strip runways with a takeoff length of less than 2000 feet.
Paved runways eventually began to appear as the desire for all-weather operations grew and as larger/heavier aircraft appeared on the scene (Boston’s Logan airport appears to have paved runways in the late 1930s). The DC-3 (16, 870 lbs) was one of the aircraft that required runways to be paved and it also needed a takeoff length of more than 3000 feet. The runway lengths needed for takeoff continue to increase, and currently the largest commercial aircraft, the Airbus A380 (610,200 lbs), needs almost 10,000 feet of takeoff length.
Boston airport in the 1920s
New York’s LaGuardia in 1939
Permanent runways were, and still are, set up in such a way to take advantage of the prevailing winds for that area. As air traffic was beginning to pick up, multiple runways could be found at major airports. A naming system was needed, and as can be seen in the 1951 edition of Annex 14, the ICAO (International Civil Aviation Organization) clearly spelled out the conventions in Section 2.1.2.1.4.1 that we still use today.
How to read runway headings:
First we need to refresh ourselves on how the cardinal directions (north, south, east, and west) relate to the numerical compass headings.
North=0° or 360° East=90°
South=180° West=270°
When we look at an aerial photo of an airport we can see that numbers are painted at the ends of the runways. First up is a close up screenshot from Google Maps showing the end of runway two-six at the Jacksonville International Airport. For any budding aviation nerds, I thought I’d also point out that the numbers are preceeded by 8 white stripes and may be followed by 6 white stripes (indicating the touch down zone).
And here is a screenshot from Google Maps that shows my home DZ’s airport. Please note that each runway is labelled on both ends.
What those numbers mean:
Runways are named according to their compass headings. Let’s assume for a moment that I am quite eccentric and I have the construction equipment and the money to build a runway that heads to the southwest. Then that runway would be named for its numerical compass heading (say 220° for our fictional runway), no matter how loudly I protest and say that I would prefer the number 25. Runways are named for their heading, not their eccentric builders.
And since a runway can be used in two directions, each runway has a number on both of its ends. My fictional runway would head 220° if used in one direction, but if I turn around to use it in the other direction then I would be heading towards the northeast, or 40°. Each runway has two sets of numbers that will always differ by 180°. Please keep in mind that runways are named for the heading of their direction of use. Stated another way, the number tells you which direction you are traveling (or heading) to, not where you have been.
However, it’s not quite that simple:
The naming rules (found in ICAO’s document Annex 14) state that runways may only have two digits, and the number assigned should be the nearest whole number that is 1/10th of the magnetic heading of the center line of the runway. And thus it was Annex 14 that sealed the fate of runways all over the world: only the numbers 01 through 36 were to be used (next time you sit next to the pilot take a look at his compass). You may have just built a runway that had a heading of 68°, but after applying the runway naming conventions, that runway would actually be designated as zero-seven (and the other end would read two-five).
Let us revisit that screenshot of my home airport and try to determine which direction is east….
We can see that Runway 9-27 is in the center of the photo.
The number 9 is painted on the left-hand side of the runway in this photo.
We know that 9 (or 09, for our international friends) stands for 90°, or east on a compass.
By using runway 9, we would be traveling from left to right in this photo.
Therefore, the right side of our photo is east and the left side is west.
You can run through that set of thinking for runway 17-35 (running from top to bottom) and find that north would be approximately 10° further clockwise from the end of the runway at the top of the photo, and south would be 10° further clockwise from the end of the runway at the bottom of the photo.
And, you may have noticed, that I have also written out the two digit numbers found at the ends of the runway from time to time. If you’ve ever listened to the radio communications in an airplane, it can sometimes be challenging to figure out what a person is saying. For clarity, the runway digits are always pronounced individually with the number 9 being pronounced as “niner.”
I’m a skydiver….why should I care?
If you held on this long then you might be wondering why a skydiver should care to understand about runway headings. Simple answer, when you are at any DZ, anywhere, at any airport, with paved runways you will always be able to figure out the cardinal directions simply by looking at the runway headings. Super helpful information for when a fellow jumper tells you that the winds on the ground are coming from the west, but winds aloft are from the north. And, you’ll never have to ask, “Which way is north?”