One may think that designing a runway is easy. Just create a road, paint markings, and that’s it, you have a runway. However, with how aviation has evolved today, runways are not only about having a long road where planes can roll. They must be well thought out, with different parts, areas, and dimensions. So yes, runways also have various parts and areas.
The Runway
The runway is the primary component of an airport, designed for the landing and takeoff of aircraft. According to the ICAO, a runway is a “rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft.” Runways can vary significantly in length and surface material, although paved surfaces are most common.
Runways are typically measured in meters, though in North America, feet are also used. Airport charts usually display both units of measurement. The length of a runway is crucial as it determines the types of aircraft that can safely operate from it. Longer runways accommodate larger aircraft and allow for longer takeoff and landing rolls.
Runways are marked with specific identifiers, including threshold markings, centerline markings, and aiming points. These markings provide visual cues to pilots, helping them maintain alignment during takeoff and landing. Runways also have lighting systems, such as runway edge lights, approach lights, and touchdown zone lights, to aid pilots in low visibility conditions.
The Stopway
A stopway is an area beyond the runway, designed to accommodate aircraft in the event of a rejected takeoff. The stopway must be strong enough to support the aircraft without causing damage. It is typically constructed from the same material as the runway and must be at least as wide.
Stopways are marked with yellow chevrons and are used only in emergencies. Building a stopway can be expensive, so airports sometimes opt to extend the runway instead. This approach provides additional runway length while still serving the stopway’s purpose.
Stopways play a crucial role in ensuring safety during takeoff. If a pilot decides to abort takeoff due to an engine failure or other issue, the stopway provides additional space to bring the aircraft to a halt. This extra safety margin can prevent accidents and reduce the risk of overruns.
The Clearway
The clearway is a defined area beyond the runway and stopway, managed by the airport to ensure it remains free of obstacles. The aircraft is never intended to be on the ground in this area during normal operations but will pass over it during the initial climb.
The clearway must allow an aircraft to achieve a specific rate of climb without encountering obstacles. According to the Federal Aviation Administration (FAA), clearways must be at least 150 meters (500 feet) wide, and the practical limit for clearway length is 300 meters (1,000 feet). Clearways can be located on land or water.
Clearways influence a pilot’s decisions during takeoff, particularly concerning flap settings. Takeoffs with extended flaps reduce the takeoff roll but also decrease the rate of climb. A longer clearway allows for safer initial climbs and greater flexibility in takeoff procedures.
Declared Distances
Declared distances are essential for understanding the usable length of a runway. ICAO mandates that these distances be published in a country’s Aeronautical Information Publication (AIP). There are four key declared distances:
- Takeoff Run Available (TORA): The length of the runway declared available and suitable for the ground run of an aircraft taking off.
- Takeoff Distance Available (TODA): The length of the takeoff run available plus the length of the clearway, providing the total distance available for an aircraft to become airborne.
- Accelerate-Stop Distance Available (ASDA): The length of the takeoff run available plus the length of the stopway, giving the total distance available for an aircraft to abort takeoff and come to a stop.
- Landing Distance Available (LDA): The length of the runway available and suitable for landing an aircraft.
These declared distances are critical for flight planning and safety. Pilots use them to determine if an aircraft can safely take off or land under specific conditions. Factors such as aircraft weight, weather, and runway conditions all influence these calculations.
Runway Safety Areas
Runway safety areas (RSAs) are surfaces surrounding the runway, designed to protect aircraft that overrun, undershoot, or veer off the runway. RSAs provide a buffer zone that reduces the risk of damage to aircraft and injury to passengers.
RSAs must be cleared and graded to specific standards, free of obstacles that could interfere with aircraft operations. They are essential for maintaining safety during takeoff and landing, particularly in adverse conditions.
Runway Shoulders
Runway shoulders are paved areas adjacent to the runway that provide additional lateral support. They help prevent soil erosion and support the weight of aircraft that might veer off the runway. Shoulders also enhance drainage and reduce the risk of standing water on the runway surface.
Runway shoulders are marked with yellow lines to distinguish them from the main runway. They are not intended for regular aircraft operations but provide a safety margin in case of deviations from the runway centerline.
Taxiways
Taxiways are routes that connect runways with other parts of the airport, such as terminals, hangars, and aprons. They allow aircraft to move safely and efficiently between different areas of the airport. Taxiways are marked with yellow centerlines and edge markings to guide pilots.
Taxiways also have lighting systems to ensure visibility in low-light conditions. They are designed to accommodate the weight and size of the largest aircraft operating at the airport. Efficient taxiway design helps reduce congestion and improve overall airport operations.
Runway Markings and Lighting
Runway markings and lighting systems are crucial for safe aircraft operations. Markings provide visual cues to pilots, helping them align with the runway centerline and identify critical areas such as the threshold, touchdown zone, and aiming points.
Runway lighting systems include:
- Runway Edge Lights: White lights outlining the edges of the runway.
- Runway End Lights: Red lights marking the end of the runway.
- Threshold Lights: Green lights indicating the beginning of the usable runway.
- Touchdown Zone Lights: White lights indicating the touchdown zone for landing aircraft.
- Approach Lights: A series of lights guiding aircraft to the runway during approach.
These lighting systems enhance safety, particularly during night operations and in poor visibility conditions.
From the primary runway to stopways, clearways, and declared distances, each component plays a crucial role in supporting aircraft takeoff and landing. Runway safety areas, shoulders, and taxiways further enhance safety and operational efficiency.
Airport authorities and aviation organizations continuously work to maintain and improve these runway components, ensuring they meet the highest standards of safety and performance.
First love never dies. I fell in love with airplanes and aviation when I was a kid. My dream was to become a pilot, but destiny led me to another path: to be an aviation digital media content creator and a small business owner. My passion for aviation inspires me to bring you quality content through my website and social accounts. Aviation is indeed in my blood and blog!
