Pist Numbering

Runway numbering is a numerical and alphanumeric coding system that defines the orientation of an airport runway relative to magnetic north and ensures standardization in flight operations. This system is based on assigning a two-digit number to each runway direction, with an additional letter added when necessary to indicate position. Magnetic direction is divided into 10-degree segments; the magnetic heading of the runway axis is rounded to the nearest 10-degree value and the final digit is dropped to form the runway number. Thus, a runway with a magnetic heading of 153° is designated as “15”, and one with a heading of 82° is designated as “08”. For orientations close to magnetic north, the value “36” is used and “00” is not employed.

Each end of a runway represents the opposite direction. Since the magnetic difference between these two directions is approximately 180°, the runway numbers for opposite ends differ by 18. For example, if one end of a runway is numbered “09”, the other end is marked as “27”.

Purpose and Application Scope

The primary purpose of runway numbering is to provide pilots with visual and standardized information regarding runway orientation. This system, in conjunction with other visual markings on the runway, forms a comprehensive identification mechanism. Runway numbers enable pilots to correctly identify takeoff and approach directions. In particular, they facilitate accurate runway selection and prevent runway confusion in conditions of low visibility or at busy airports with parallel runways.

Use of Letters for Parallel Runways

When an airport has multiple runways aligned in the same magnetic direction, the runways are distinguished by their positional location. In such cases, a letter indicating position is appended to the runway number.

• L (Left): Left runway
• R (Right): Right runway
• C (Centre): Centre runway

At an airport with two parallel runways, the runways are designated as “09L/27R” and “09R/27L”. For three parallel runways, the designations are “09L”, “09C”, and “09R”. At airports with more than three parallel runways—for example Los Angeles or Atlanta—some runways are renumbered by shifting their magnetic alignment to avoid confusion between similar designations; for instance, 36L/36R and 35L/35R. This adjustment aims to prevent ambiguity among similarly named runways.

Marking Format and Application Standards

Runway numbers are painted in white, using bold, high-contrast characters at the runway threshold. Their application is mandatory on paved runways and recommended on unpaved runways. The digits and letters are drawn according to dimensions, proportions, and placement rules specified in ICAO Annex 14 and national standards.

The threshold area where the numbering is located marks the beginning of the usable portion of the runway. It is positioned on the same plane as or immediately behind the threshold markings. If the numbers are integrated with the threshold lines, the character size is increased to fill the space between the lines. On parallel runways, the letter designating position typically follows the number—for example “08L”.

Runway numbers are symmetrically placed along the runway’s long axis. The accuracy and visibility of the markings are regularly inspected based on the condition of the surface, ambient lighting conditions, and maintenance frequency.

Relationship with Visual Aid Systems

Runway numbers are one of the key elements of the runway marking system. This system works in conjunction with runway threshold markings, the centreline, the aiming point, the touchdown zone, and edge lines. Together, these markings provide pilots with a sequential and hierarchical visual guidance system during approach.

The numbering is also integrated with runway lighting systems. Runway threshold lights are green, runway end lights are red, edge lights are white, and centreline lights alternate between white and red. This arrangement supports accurate identification of runway direction, particularly under low visibility conditions.

Relationship with Safety Areas

Although runway numbering directly relates to directional identification, it is part of a broader design framework that includes the runway’s geometric structure and safety areas. The Runway End Safety Area (RESA) is a designated zone beyond the runway end intended to reduce the risk of aircraft damage in the event of an overrun or undershoot. These areas are symmetrically arranged along the runway axis. According to ICAO and SHGM standards, the minimum RESA length for Code 3 and Code 4 runways is 90 metres, with a recommended length of 240 metres.

Magnetic Variation and Renumbering

As the Earth’s magnetic field changes over time, the magnetic orientation of runways may also shift. This gradual drift can cause runway numbers to become inaccurate. When periodic measurements of magnetic declination indicate that a runway’s magnetic heading has shifted into a different 10-degree segment, the runway is renumbered. For example, a runway with a magnetic heading of 144° may retain the designation “14” even as it shifts to 146°; however, once it exceeds 147°, it is renumbered to “15”. These updates are simultaneously reflected in aviation charts and ground markings.

Special Cases and National Practices

In some countries, particularly regions with high magnetic variation, runways may be numbered based on true north rather than magnetic north. This practice is adopted to avoid frequent renumbering.

In Türkiye, runway numbering and marking standards are detailed in the document “Airport Runways” published by the General Directorate of Civil Aviation. This document defines runway orientation, length, width, slope, safety areas, marking dimensions, and geometric requirements in accordance with ICAO norms.

Runway numbering is the fundamental system that ensures the international standardization of runway orientation in aviation. It enables pilots to select the correct runway, allows air traffic control to safely direct aircraft, and supports the maintenance of global standardization. This numbering system, based on magnetic north and integrated with visual identification, lighting, and runway geometry, enhances the safety of airport operations.