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Runway

technology Maturity 9-11 Next article →

A runway is an elongated, rectangular surface designed for aircraft to land and take off. These surfaces are vital for aviation safety and efficiency. Most runways are human-made using materials like asphalt, concrete, or a mixture of both. However, some runways use natural surfaces such as grass, dirt, gravel, ice, sand, or salt. While people often use the word "tarmac" to describe these areas, very few runways are actually constructed from tarmac. For seaplanes, takeoff and landing areas on water are called waterways.

Palm Springs International Airport photo Don Ramey Logan
Palm Springs International Airport photo Don Ramey Logan

The design of a runway depends heavily on the wind. Engineers must consider the prevailing wind, which is the direction the wind blows most often. To avoid dangerous crosswind operations, runways are aligned with this wind direction. Taking off and landing into a headwind is a major advantage. This movement increases the relative airspeed of the aircraft, which creates more lift. Lift is the force that allows an aircraft to fly. Because of this extra lift, a plane can reach takeoff velocity with a shorter ground roll. It also allows the aircraft to land with a slower ground speed.

To decide where to build, experts analyze a wind rose. This tool shows the prevailing wind directions for a specific location. In the 1920s and 1930s, many airports used a triangular pattern. They built three runways at 60° angles to each other. This was because early aviation experts did not fully understand wind behavior. Eventually, the runway with the most traffic would become the main runway. The other two were often abandoned or turned into taxiways.

China lake
China lake

Runways have changed significantly as aircraft technology has advanced. In January 1919, Orville Wright noted that preparing flat ground was an expensive task. During the 1930s, many army planes used "all-over fields." These were circular, groomed, and drained areas of turf. However, as aircraft grew larger, their tire pressures increased. These tires required more than 70 psi, which the grass fields could not handle. By 1928, Ford Airfield became the first U.S. airport with concrete runways. By 1932, all major U.S. airports had installed runways.

McDonnell Douglas MD-11 KLM - Royal Dutch Airlines, AMS Amsterdam (Schiphol), Netherlands PP1151411211
McDonnell Douglas MD-11 KLM - Royal Dutch Airlines, AMS Amsterdam (Schiphol), Netherlands PP1151411211

Runways are identified by specific numbers between 01 and 36. These numbers represent the magnetic azimuth, or the compass heading, of the runway. This heading is based on magnetic north rather than true north. For example, runway 09 points east at 90°. Runway 18 points south at 180°. Runway 27 points west at 270°. Runway 36 points north at 360°. Because a runway can be used in both directions, it has two names. If one end is runway 15, the opposite end is runway 33. The numbers always differ by 18. Pilots pronounce each digit individually, such as "one-five," to ensure clear radio communication.

Runway 22
Runway 22

At large airports, multiple runways may run parallel to each other. To tell them apart, engineers add letter suffixes: L for left, C for center, and R for right. For instance, you might see runways 15L, 15C, and 15R. At very large airports like Chicago O'Hare or Dallas/Fort Worth, the numbering system can become complex. Some airports shift identifiers by one to avoid confusion when they have four or more parallel runways. Other suffixes exist for special uses. The suffix "W" is used for waterways. Other letters can denote specific aircraft, such as "G" for gliders or "H" for rotorcraft.

15R-33L - Aeropuerto de Madrid-Barajas - detail
15R-33L - Aeropuerto de Madrid-Barajas - detail

Runway names must sometimes change due to magnetic drift. As the Earth's magnetic field shifts, the magnetic heading of a runway changes. This is a common issue at higher latitudes. For example, Fairbanks International Airport renames its runways roughly every 24 years. When a renumbering happens, it is usually done at night. Workers must repaint the numbers and change the taxiway signs.

ORD Airport Diagram
ORD Airport Diagram

Finally, pilots rely on specific measurements regarding available distance. Takeoff Run Available (TORA) is the length suitable for the ground run during takeoff. Takeoff Distance Available (TODA) includes the TORA plus any available clearway. Accelerate-Stop Distance Available (ASDA) includes the takeoff run plus a stopway. Landing Distance Available (LDA) is the length suitable for the ground run during landing. These precise measurements ensure that every takeoff and landing is performed within safe limits.

Aim fig 4-3-5 Declared Distances with Full-Standard Runway Safety Areas, Runway Object Free areas, and Runway Protection Zones
Aim fig 4-3-5 Declared Distances with Full-Standard Runway Safety Areas, Runway Object Free areas, and Runway Protection Zones
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🖼️ Images & Media (18)
File:Palm Springs International Airport photo Don Ramey Logan.jpg
Palm Springs International Airport photo...
File:McDonnell Douglas MD-11 KLM - Royal Dutch Airlines, AMS Amsterdam (Schiphol), Netherlands PP1151411211.jpg
McDonnell Douglas MD-11 KLM - Royal Dutch...
File:China lake.jpg
China lake.jpg
File:Runway 22.svg
Runway 22.svg
File:Runway landing designator marking-Numbers.svg
Runway landing designator marking-Numbers.svg
File:ORD Airport Diagram.svg
ORD Airport Diagram.svg
File:15R-33L - Aeropuerto de Madrid-Barajas - detail.jpg
15R-33L - Aeropuerto de Madrid-Barajas -...
File:Aim fig 4-3-5 Declared Distances with Full-Standard Runway Safety Areas, Runway Object Free areas, and Runway Protection Zones.jpg
Aim fig 4-3-5 Declared Distances with...
File:RunwayDiagram.png
RunwayDiagram.png
Airport lights 1.webp
File:Runway Landing Light.jpg
Runway Landing Light.jpg
File:A320-cockpit-night.jpg
A320-cockpit-night.jpg

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