What Do All Those Signs at the Airport Mean?
Have you ever looked out of an airplane window and wondered what all those runway markings, runway signs, landing markings, landing signs, and lights actually mean? If so, then you are in luck, as we have prepared a short guide to explain what they all actually signify.
Please note that this guide is not intended to be comprehensive, so if you want to dig a little deeper the Federal Aviation Administration (FAA) is the de facto source for all your queries on this subject. The FAA, in case you are not aware, is the central authority for most international airports.
What is the meaning of runway markings?
If you spend your time immersed in a good book or reading a paper during flights, you might expect the pilot to touch down on the nearest patch of asphalt/concrete possible during a landing. This is definitely not the case.
In fact, all those colorful markings, lights, and other signs all play their part in telling pilots where they can, and cannot, place their aircraft during takeoff and landing. These standards are, as you are about to find out, critically important to prevent accidents that could spell disaster for all concerned.
Given the importance of standardized markings, most international airports follow the same set of standards that are defined by the FAA's advisories on runway markings.
1. The "blast pad" is vitally important
The first and one of the most important sets of runway markings is the so-called "blast pad." While it has a very impressive term, its function is a little less dramatic.
The "blast pad" is the yellow-chevroned section at the start (and end depending on the aircraft's position) of the runway. As the name suggests, this area is intended to absorb or resist the exhaust "blast" or "jet wash" from the jet engines without compromising the main section of the runway or surrounding area, objects, and importantly, people. In fact, this area of the runway is generally not designed to take the weight of an aircraft at all.
2. The "threshold" is the start of the runway proper
The runway proper begins with another runway marking called the "threshold." This is just what it sounds like: a number of thin, long lines that are used to indicate the width of the runway. They come in two main forms and can either consist of eight longitudinal stripes of uniform size and shape or more stripes depending on the width of the runway (like at Heathrow runway 27R pictured above).
The threshold markings denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions. According to the FAA, "a threshold marking helps identify the beginning of the runway that is available for landing. In some instances, the landing threshold may be relocated or displaced."
There may, or may not, also be a series of large arrows between the "blast pad" and the "threshold," depending on the airport and runway. This area is called the "displaced threshold" and is an area usually used for taxiing. It is not generally designed to support repeated landings, however,
3. The runway's name or designation comes next
Directly above the threshold area, you will find a number, sometimes followed by a letter. These, according to the FAA, denote the runway name and the number corresponds to, "the nearest one-tenth magnetic azimuthal centreline of the runway". It also corresponds to the direction of the approach of an incoming aircraft.
Given that there are 360 azimuthal degrees, runway numbers will only ever go up to 36.
The letter enables the airport in question to discriminate between two parallel runways (left or right), if present.
4. The centreline is another important runway marking
The dashed line along the middle of a runway is called the center-line for obvious reasons. This runway marking acts as a visual aid for the pilots — just like similar road markings do for car drivers.
These markings help the pilot orientate the aircraft during takeoff and landing. At some airports, these may change color to red towards the last few thousand feet or meters of the runway.
6. The "aiming point" and "touchdown zone" markings are very important runway markings
So far so good, but none of the above markings are actually intended to be "landed on," per se. In fact landing on the "blast pad," in particular, might be catastrophic, but can be used, on occasion, for taxiing and maneuvering.
To those of us who are not trained pilots, the "touchdown zone" section of the runway is easy to miss. From the above image, you will notice a series of larger, evenly spaced vertical lines on either side of the centreline after the runway number. These are called the "touchdown zone" and provide an unambiguous visual aid to pilots during landing. The touchdown zone is, as the name suggests, the portion of a runway, beyond the threshold, where it is intended that a landing airplane first contacts the runway.
The more observant among you will also notice two thicker, and larger, similar markings too. These are called the "aiming points," and they're what the pilots are supposed to be looking at when coming in for a landing.
What do all the numbers, colors, and signs on runways mean?
With regards to colored markings, generally speaking, anything painted white is reserved for the actual runway itself while yellow is all about taxiing or, in some cases, designates no-go zones.
All well and good, but what about the other numbers, and signs on (or close to) a runway? What do they mean?
With regards to the markings, everything is regulated, once again, by organizations like the FAA. For example, the FAA's guidelines include provisions for the number "1" having a horizontal tip to avoid confusion. And that all text must be 60 feet high (18.2 meters), except the numbers "6" and "9" because of their "tails".
When removing obsolete characters, the airport must sandblast, shot blast, water blast, or chemically remove them, not paint over them. This is to prevent the new marking from decaying and revealing the old information. That explains the light-colored spots or words you may see on the runway.
When taxiing to the runway from the terminal, you may have also seen large red markings just before the runway. Called "holding positions", these act like stop signs for an aircraft while it's taxiing or waiting to take off.
The numbers are there to help the air traffic controller coordinate aircraft comings and goings.
When a pilot reaches a short line at a runway entrance the red block denotes which runway the pilot is about to enter. For example, "18-36" indicates that "Runway 18" runs from left to right and "Runway 36" runs from right to left. This information is usually also painted on the tarmac.
Gates are identified with yellow numbers and markings when the aircraft gets closer to the terminal building.
What do the lights mean on a runway?
An organization like the FAA not only assigns standards to paint and signage, but also to the lighting.
Depending on where you sit as a passenger and the kind of plane you're traveling in, you may not appreciate the myriad of lights that pilots must obey. Generally, however, you'll most likely see blue lights. These indicate the taxiway edges or, if they are white, will indicate the touchdown area of the runway.
According to the FAA, green lights designate the threshold, where the actual runway starts, while red always means exactly what you think it means: do not go!
The centerline of the runway is usually indicated by a series of white or red lights for most of the length of the runway. Towards the last few hundred feet/meters these will alternate between red and white, and finally, become red towards the end of the runway.
There may also be a series of horizontal white lights in the "touchdown" area of the runway too.
You may also notice a series of red and white lights when approaching a runway. These form distinctive short lines of light that begin long before the runway. They are very powerful and important lights for pilots and are called approach lights.
These act as important visual aids for the pilot when making their final approach to the runway.
After the approach lights, there is a further wider line of light that directly precedes the runway. This provides an aide for pilots at a critical phase in landing.
These lights will appear red or white depending on the angle of approach. Called the precision approach path indicator (PAPI) these lighting systems can consist of a single row of either two or four light units and visible from at least 5 miles (8 km) out in the daytime and 4 times that at night.
If the pilot sees four white lights, this usually indicated they are too high. Four red lights, conversely, mean their approach is too low. They want to aim for two white, and two red lights.
Another form of lights you might see on the runway is called amber guard lights. These lights are used to tell pilots (and service vehicles) that they are approaching an active runway.
For most lights, steady burn incandescent lighting is generally used, but there has been an increase in the use of LEDs on taxiways and runways across the globe over the last few years.
What is the importance of a wind cone?
Another interesting visual aid you may see near a runway is the wind cone, or windsock. These should be available at the end/beginning of each runway where they can area easily visible by the pilot, they also need to be lit at night too.
They need to be colored in distinct colors to contrast with their surroundings and can be between 8 (2.4 meters) and 12 feet (3.6 meters) long.
They act as a basic visual aid to tell the pilot the current wind direction and approximate speed or intensity prior to takeoff. Windsocks need to be able to rotate freely around their mounting pole and should show at least wind speeds of 3 knots (5.5km). When fully extended the windsock should be able to designate wind speeds of 15 knots (27.8km) or more.
If the windsock has variegated colors, each bar helps to give a rough idea of the wind speed too. For each bar fully extended, the wind speed is roughly a multiple of 3 knots (5.5 km/h).
So there you have it; your plane journeys will never be the same again. Now you can show off to your loved ones what all those colorful signs, markings, and lights mean next time you jet off to some far-flung destination.