In this article, we will define parts and extensions of runways: Clearway, Stopway, TORA (Take of Run Available), TODA (Take of Distance Available), ASDA (Accelerate-Stop Distance Available) and LDA (Landing Distance Available). All these parts serve for safety operations of aircraft. It may be a little bit confusing. But the figure showing the relation between them will help and ease the issue for understanding. You can find the figure below.
First of all, let we define “What Runway is”.
According to ICAO (International Civil Aviation Association), runway is defined as “rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft”. Moreover, runway surfaces can be made of various special materials like asphalt, concrete, or a mixture of both. On the other hand, in some domestic airfields runways may be natural surface like grass, dirt, gravel, ice, sand or salt. Commonly runway length is given as meters, just in North America it is given by feet.
Clearway is the area beyond the runway not less than 152 meters wide, centrally located about the extended centerline of the runway and under the control of airport authorities. It is expressed as a plane extending from the end of runway with up slop not exceeding 1.25% above which no object or terrain protrudes with exception of threshold lights.
Stopway is the area at the end of take-off runway no less wide than the runway and centered upon extended centerline of runway. This area is able to support the aircraft during an aborted take-off without causing structural damage to the aircraft.
TORA (Take off Run Available)
TORA is defined as length of runway suitable for takeoff run of an aircraft. If there exists a displaced threshold TORA is not equal to LDA (Landing Distance Available). On the other hand, TORA doesn’t include Stopway or Clearway.
TODA (Take off Distance Available)
TODA is the length of runway plus any clearway if exists. In case no clearway exists, TODA is same as TORA. In detail, TODA includes ground as well as air segments.
ASDA (Accelerate-Stop Distance Available)
ASDA a distance and is defined as sum of LDA/TORA (as applicable) and Stopway. In case take off is aborted the aircraft can be brought to a stop either on the runway or on Stopway. ASDA must not be used as TORA because of the structure of the Clearway area.
LDA (Landing Distance Available)
LDA is the portion of runway length declared available and suitable for landing of an aircraft. If there exists a displaced threshold LDA starts from beginning of displaced threshold. Otherwise beginning of the threshold is the beginning point of LDA.
Information about Clearway, Stopway, TORA, TODA, ASDA, LDA and other details for relevant runways can be obtained from Aerodrome Information Publications, Jeppesen Charts.
These lengths and values are very important for aerodrome authority, air traffic controllers of the airport and the pilots of the aircraft. There are various types of aircraft in different categories and all have some minimum requirements. An airline company has to fulfill these requirements to build a destination.
From an air traffic controller side, ATC must know all lengths with intersection takeoff values to success and build a safety environment.
For all technical details, rules and regulations in aviation serve firstly to one purpose and that’s “Safety”.
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