What is Runway?
A runway is a specified rectangular area on a land aerodrome (airport) that is prepared for aircraft landing and takeoff. According to the International Civil Aviation Organization (ICAO), runways can be either man-built (usually consisting of asphalt or concrete) or natural (grass, dirt, gravel, ice, sand, or salt). A runway’s principal function is to provide a safe and unobstructed path for airplanes to land and take off.
It is preferable for stationary airplanes to take off and land facing the wind. This allows them to take off and land more effortlessly and quickly. Large airports typically have many runways pointing in various directions. They can select the one that is best aligned with the wind. When an airport has just one runway, it is generally designed to face the usual wind direction. People sometimes use a wind rose to assess wind patterns before constructing runways. Wind direction refers to where the wind is blowing from. For example, if a plane takes off from runway 09, it will be flying east into a “east wind” from 090°.
Naming
Runways are named after numbers between 01 and 36, which signify the magnetic direction of the runway’s heading in decadegrees. This direction is determined by the local magnetic declination, which deviates from true north. For example, a runway numbered 09 faces east (90°), 18 points south (180°), 27 points west (270°), and 36 points north (360°, corresponding to 0°).
When a plane takes off or lands on runway 09, it is traveling east at around 90 degrees. Runways can be used in both directions and are labeled differently for each. For example, “runway 15” in one direction becomes “runway 33” in the opposite direction, with the two numbers diverging by 18 (equivalent to 180°).
Image: Runway 22 Source: Wikipedia
Letter suffix
When numerous parallel runways align in the same direction, each runway is differentiated by appending left (L), center (C), or right (R) to the number identification. When viewed from their designated direction, runways might be termed one-five-left (15L), one-five-center (15C), and one-five-right (15R). The designation changes when the same runway is used in the other direction. A runway designated as zero-three-left (03L) becomes runway two-one-right (21R), with the new number calculated by adding 18 to the old number, signifying the 180° difference when entering from the other direction. Certain nations have restrictions stating that only one of the closely located parallel runways may be operational at any given time, especially under poor weather circumstances.
Image Source: Wikipedia
Renumbering
Because to the steady drift of Earth’s magnetic lines and the related alterations in magnetic direction, runway designations may vary over time. The location of the airport and the amount of magnetic drift experienced impact the changing of runway IDs. Runways are often allocated headings that are rounded to the closest 10 degrees, causing certain runways to be affected sooner than others. For example, if a runway has an initial magnetic heading of 233°, it is labeled as Runway 23. Even if the magnetic heading drops 5 degrees to 228°, the runway will still be designated as Runway 23. If the initial magnetic heading was 226° (Runway 23), then it drops by only 2 degrees to 224°, the runway is classed as Runway 22.
Because of the slow nature of magnetic drift, runway designation changes are uncommon. Such modifications are often undesirable since they need adjustments to aeronautical charts and descriptive documentation. When a runway designation is changed, especially at big airports, it is usually done at night. This date was chosen because it requires upgrading taxiway signs and repainting runway numbers to match the new designators. In July 2009, for example, London Stansted Airport in the United Kingdom changed its runway designations from 05/23 to 04/22 during the night.
Declared Distances
Declared distances are key runway specifications that define precise lengths beyond the physical runway usable for aircraft operations. Takeoff Run Available (TORA), Takeoff Distance Available (TODA), Accelerate-Stop Distance Available (ASDA), and Landing Distance Available (LDA) are examples of these lengths. TORA denotes the runway length available for takeoff, TODA denotes the total distance available for takeoff, ASDA is the accelerate-stop distance, and LDA denotes the runway length available for landing.
Sections of a Runway
Runways are separated into several portions, each with its own function. The runway threshold, runway strip, displacement threshold, and runway end safety area (RESA) are among these portions. The runway’s beginning point is the threshold, but the displaced threshold is a specified location where landings are not authorized. The runway strip surrounds the runway and its related shoulders, adding extra safety margins. The RESA is a runway extension designed to improve safety in the event of overshooting or undershooting during takeoff or landing.
Markings
Runway markers are important visual aids that help pilots through various phases of flight. Threshold markings, aiming point markers, touchdown zone markings, and taxiway holding position markings are examples of these markings. Aiming point markers aid pilots in aligning their aircraft during approach, touchdown zone markings define the best touchdown region, and taxiway holding position markings suggest where aircraft should halt while taxiing.
Surface Characteristics
A runway’s surface is precisely constructed to withstand the enormous pressures and strains generated by airplanes. Asphalt and concrete are common runway surfaces. Surface roughness, friction, and drainage are all carefully addressed factors to provide maximum aircraft performance and safety.
Surface Abbreviations and Meanings
| Abbreviation | Meaning |
|---|---|
| ASP | Asphalt |
| BIT | Bituminous asphalt or tarmac |
| BRI | Bricks (no longer in use, covered with asphalt or concrete now) |
| CLA | Clay |
| COM | Composite |
| CON | Concrete |
| COP | Composite |
| COR | Coral (fine crushed coral reef structures) |
| GRE | Graded or rolled earth, grass on graded earth |
| GRS | Grass or earth not graded or rolled |
| GVL | Gravel |
| ICE | Ice |
| LAT | Laterite |
| MAC | Macadam |
| PEM | Partially concrete, asphalt, or bitumen-bound macadam |
| PER | Permanent surface, details unknown |
| PSP | Marston Matting (derived from pierced/perforated steel planking) |
| SAN | Sand |
| SMT | Sommerfeld Tracking |
| SNO | Snow |
| U | Unknown surface |
| WAT | Water |