# How are runways numbered?

Danny Beckett
• How are runways numbered? Danny Beckett

I'm not a professional pilot, just an enthusiast, so this might seem obvious to others; but I noticed that airports don't use sequential numbering for runways, starting from 1.

Liverpool (for example) has runway 9/27; so how are these numbers assigned? Also, what do Left and Right signify?

• Runway numbers are determined by their heading, e.g. for Liverpool, runway 9/27 is facing approx. magnetic heading 90° in one direction, and 270° in the opposite direction.

If an airport has parallel runways, these would then be marked Left, Center and Right, e.g. 9L/9C/9R.

• The information from the US AIM may be useful here:

b. Runway Designators. Runway numbers and letters are determined from the approach direction. The runway number is the whole number nearest one‐tenth the magnetic azimuth of the centerline of the runway, measured clockwise from the magnetic north. The letters, differentiate between left (L), right (R), or center (C), parallel runways, as applicable:

1. For two parallel runways “L” “R.”

2. For three parallel runways “L” “C” “R.”

As to why the numbers are 1, 9 or something else, that is determined by the local prevailing wind conditions among other considerations (terrain etc.). Aircraft always take off or land into the wind (as far as possible), so that is a key factor in how runways are positioned. NASA has a very good article on airport layouts that goes into more detail.

• Runways are usually numbered according to their direction. Consider a plane flying toward the runway on final approach. Divide its magnetic heading by 10 and you'll usually get the runway number. Runway 35 will be a runway used for landings (and takeoffs) to the north, for example.

Opposite ends of the same runway have different numbers, 18 (which represents 180 degrees) apart. A runway with 35 for landings to the north will have runway 17 for landings to the south. Even though these are the same strip of concrete, they are treated as separate runways by pilots and controllers.

If there are two airports near one another with runways at the same angle, sometimes one of the airports will add or subtract one from the runway number to help planes differentiate between the airports.

Occasionally a runway number will change when the magnetic declination angle changes across 5 degrees.

Some runways in areas of large magnetic declination use true instead of magnetic headings for the runway numbers. This is not unusual in northern Canada and Greenland.

When there is more than one parallel runway at an airport, L, R, or C may be appended to the runway number for Left, Right, or Center. These are based on the approach direction, so, for example, the runway 35L would be called 17R from the opposite direction.

Tags
• I'm very interested to learn if there are (m)any (major) (commercial) airports that have runways further away from the terminal(s) than Schiphol's Polderbaan. Which airport is "in the lead" in this respect? The northern end of the Polderbaan, the last runway to be constructed, is 7 km (4.3 mi) north of the control tower, causing taxi times of up to 20 minutes to the terminal. [...] Newest runway, opened 2003. Located to reduce the noise impact on the surrounding population; aircraft have a lengthy 15-minute taxi to and from the Terminal. Wikipedia

• A few times, when flying into SFO, me and my fellow passengers were informed that due to foggy weather one of two parallel runways there is closed, causing delays. So, a few questions: Why can only one runway be used during fog? During an instrument landing, if the instruments are precise enough to land the plane exactly in the middle of one runway, then surely they are precise enough to differentiate between two runways? Is this standard practice in all airports or something specific to SFO? Is there some minimum distance between parallel runways above which it is safe to keep them both

• I'm not a professional pilot, just an enthusiast, so this might seem obvious to others; but I noticed that airports don't use sequential numbering for runways, starting from 1. Liverpool (for example) has runway 9/27; so how are these numbers assigned? Also, what do Left and Right signify?

• I've never had the opportunity to fly into a controlled airport with parallel runways, so I've never actually faced the situation. But, in the interest of being ahead of it, when would it be prudent to switch to ground frequency with this clearance (assume I just landed)? N12345, right on E, cross 27 R, contact ground .9 Should I call ground (or switch frequency, so I no longer hear the tower) before or after crossing 27 R? My by-the-book assumption would be immediately, as there's no "then" or "after crossing" or similar, but somehow that feels wrong. I suppose normally it doesn't

• Let's say we have a Cessna 150 or some other lightweight two seater and no chance to land with head wind for whatever reason. We're trying to land with a constant tailwind of 7 knots. I would try to land as close to stall speed as possible to compensate the tailwind. So much for the theory. In reality, the wind is not constant. If I'm close to stall, dying wind will give me trouble. What's a general good approach for such situations? What configuration would you choose? If the runway is very long, one can just go faster. But often, runways are rather short.

• Forgive my total lack of aviation knowledge. I just flew out of SFO and was fascinated by the fact that pairs of planes alternated between departing on 28L + 28R (simultaneously) and arriving on 19L/R. My question is this: What amount of micromanagement from ATC exists to keep taking-off planes on schedule and not running into the landing planes, especially in cases where runways cross? How much information does the tower give to the taxiing planes? Thanks!

• Whenever I sit in an aircraft and we taxi around the airport, I wonder how exactly is the airport organized, for example, the arrangement of the taxiways and runways. Is it possible to locate airport diagrams? I'm mostly interested in Paris CDG, Prague PRG and Amsterdam AMS.

• Primary target: An aircraft not reporting mode-C, the only thing the controller has is the return on the radar. When a controller reports a primary target as traffic to other aircraft, the controller does not have the altitude of the target. Given this, I conclude that ATC radar does not have the altitude (angle-up) to the target, and only provides azimuth. So then without the altitude, how... miles out. However, if the target is at 15,000ft, the proper position would be 9.5 miles out. Since the difference is so small, does the radar just put the target at 10 miles, and the FAA separation

• After answering this question on History.SE, I started to wonder if it would be possible to find out even more detail about the plane now that its serial number is known. I have no idea what kind of flight records the US Army Air Corps kept, however. I know most flight logs today are kept by pilot, but I imagine there would be some way to trace what pilots flew a particular plane. I have no idea if this is possible for USAAC trainer planes in the 1930s. Could I get access to these records? If so, how would I go about it? I'm mostly interested in seeing if I can find out more information

• I thought that you had to perform all your ATPL multi-crew time in aircraft with a certificated minimum of 2 crew, but I've heard of some pilots using time in single-pilot aircraft towards their EASA ATPL licence. Is this true? If so, could someone explain how is this possible?

Data information