المدرج (RWY: Runway)

What Is a Runway?

A runway (RWY) is the defined rectangular surface at an aerodrome prepared for the landing and takeoff of aircraft. It is the most critical and tightly regulated piece of airport infrastructure, designed to specific dimensions, surface specifications, and marking standards governed by ICAO Annex 14. A runway's dimensions, orientation, surface condition, lighting, and available navigational aids directly determine which aircraft can use it, in what weather conditions, and with what payload — making runway characteristics central to airline network planning and operational safety.

How It Works

Runways are identified by their magnetic heading rounded to the nearest ten degrees divided by ten — so a runway aligned at approximately 090° (due east) is designated Runway 09. The reciprocal direction (270°, due west) is Runway 27. Where two parallel runways exist, they are suffixed Left (L), Centre (C), or Right (R): 27L and 27R. Runway condition is reported as the Runway Condition Code (RwyCC) or mu (friction coefficient) for contaminated surfaces. Declared distances — TORA (Takeoff Run Available), TODA (Takeoff Distance Available), ASDA (Accelerate-Stop Distance Available), and LDA (Landing Distance Available) — specify exactly how much runway length is legally available for each phase of a departure or arrival. Instrument Landing System (ILS), RNAV/GNSS, or visual approach procedures are published for each runway end.

Types and Standards

• Instrument runway: Equipped with ILS, PAPI, and lighting for IMC operations; the majority of commercial runways.
• Precision approach (CAT I/II/III): ILS precision approach runways certified for progressively lower visibility minima — CAT IIIc theoretically allows zero visibility operations.
• Stopway / clearway: Areas beyond the TORA that extend TODA and ASDA for performance purposes, not paved to full runway strength.
• EMAS (Engineered Materials Arresting System): Crushable concrete or foam beds at the end of short runways to decelerate overrunning aircraft safely.

Interesting Facts

• The world's longest commercial runway is at Qamdo Bamda Airport (ZUBD) in Tibet, at 5,500 metres — required to compensate for the extremely high altitude (4,334 m AMSL) which severely reduces engine thrust and aerodynamic lift.
• Heathrow's two runways handle over 480,000 movements per year — an extraordinary intensity achieved through precise sequencing that leaves as little as 90 seconds between landing aircraft.
• The bright white "piano key" markings at each runway threshold are a universal ICAO standard; they are not merely decorative — their width and number encode the runway width to pilots on approach.
• Runway rubber removal — grinding off accumulated tyre rubber deposits from the touchdown zone — is required periodically to maintain surface friction above the minimum acceptable coefficient.