April 4, 2022

Runways explained

Smoke On Go

Whether you have been flying for a long time, or just started, here are some runway things you might not know or might have forgotten about.

According to the ICAO (International Civil Aviation Organnization), a runway is a “defined rectangular area prepared for the landing and takeoff of aircraft.

As for seaplanes and floatplanes, takeoff and landing areas defined on the surface of water are generally referred to as waterways.

HISTORY

In 1916, in a World War I war effort context, the first concrete-paved runway was built in Clermont- Ferrand in France.

NUMBERING

Runways are named by a number between 01 and 36, which is generally the magnetic azimuth of the runway’s heading in degrees. This heading differs from true north by the local magnetic declination. A runway numbered 09 points east (90°), while runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to the north (360°, not 0°).

A runway can normally be used in both directions, and is named for each direction separately.

If there is more than one runway pointing in the same direction (parallel runways), each runway is identified by appending left (L), center (C) and right (R) to the end of the runway number to identify its position (when facing its direction).

RENUMBERING

Runway designations may change over time because Earth’s magnetic lines slowly drift on the surface and the magnetic direction changes. Depending on the airport location and how much drift occurs, it may be necessary to change the runway designation. As runways are designated with headings rounded to the nearest 10°, this affects some runways sooner than others. Because magnetic drift itself is slow, runway designation changes are uncommon, and not welcomed, as they require an accompanying change in aeronautical charts and descriptive documents.

DISTANCE (LENGTH)

Takeoff and landing distances available are given using one of the following terms:

TORA– Takeoff Run Available.

TODA – Takeoff Distance Available.

ASDA – Accelerate-Stop Distance Available.

LDA – Landing Distance Available.

EMDA – Emergency Distance Available – LDA (or TORA) plus a stopway.

SECTIONS

There are standards for runway markings:

The runway thresholds are markings across the runway that denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions.

The runway safety area is the cleared, smoothed and graded area around the paved runway. It is kept free from any obstacles that might impede flight or ground roll of aircraft.

The runway is the surface from threshold to threshold (including displaced thresholds), which typically features threshold markings, numbers, and centerlines, but excludes blast pads and stopways at both ends.

Blast pads are often constructed just before the start of a runway where jet blast produced by large aircraft during the takeoff roll could otherwise erode the ground and eventually damage the runway.

Stopways, also known as overrun areas, are also constructed at the end of runways as emergency space to stop aircraft that overrun the runway on landing or during a rejected takeoff.

MARKINGS

There are runway markings and signs on most large runways. Larger runways have a distance remaining sign (black box with white numbers). This sign uses a single number to indicate the remaining distance of the runway in thousands of feet. For example, a 7 will indicate 7,000 ft (2,134 m) remaining.

THREE TYPES OF RUNWAYS

Visual runways are used at small airstrips and are usually just a strip of grass, gravel, ice, asphalt, or concrete. Radio communication may not be available and pilots must be self-reliant.

Non-precision instrument runways are often used at small- to medium-size airports. Precision instrument runways, which are found at medium- and large-size airports.

RUNWAY WIDTH

The threshold stripe markings represents the runway’s width. The threshold markings are 150 feet long and 5.75 feet wide.

They’re usually found on runways with instrument approaches, and are required on runways serving approach Category C and D airplanes. Threshold markings are also required on runways used by international commercial transport.

LIGHTING

A line of lights on an airfield or elsewhere to guide aircraft in taking off or coming in to land or an illuminated runway is sometimes also known as a flare path. The runway threshold is marked by a line of green lights.

Runway lighting are used at airports for use at night and low visibility. Seen from the air, runway lights form an outline of the runway. A runway may have some or all of the following.

LIGHTING CONTROL

Typically the lights are controlled by a control tower, a flight service station or another designated authority. Some airports/airfields (particularly uncontrolled airfields) are equipped with pilot- controlled lighting, so that pilots can temporarily turn on the lights by use of the radio when the relevant authority is not available.