Following are the available take-off lengths declared by appropriate authorities and ICAO for for different airfields. Knowledge on these terms is important for performance calculations.
Clearway, Stopway, TORA, TODA, ASDA & LDA
Clearway is the area beyond the runway not less than 152m wide centrally located about the extended centerline of the runway and under the control of airport authorities. Clearway 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.
Characteristics of Clearway:
- centrally located about the extended center line of the runway
- under the control of appropriate airport authorities
- be expressed in terms of a clearway plane extending upward slope not exceeding 1.25%
- have minimum width not less than 152m
- have no protruding objects or terrain
- only threshold lights may protrude above the plane, if their height above the end of the runway is 0.66m (26 inch) or less, and if they are located on each side of the runway
Stopway is the area at the end of take-off runway no less wide than the runway and centered upon extended centerline of runway and able to support the aeroplane during an aborted take-off without causing structural damage to the aeroplane.
characteristics of Stopway:
- at least as wide as the runway and centered upon the extended center line of runway
- able to support airplane during aborted take off without causing any structural damage
- designated by airport authorities for use in decelerating the airplane during an aborted take off
TORA (Take off Run Available)
TORA is the length which is available (declared available by appropriate authority) and suitable for ground run of an aeroplane during takeoff. TORA does not include Stopway or Clearway.
TORA is either equal to the runway length, or to equal to distance from runway entry point(intersecting taxiway) to the end of the runway.
TODA (Take off Distance Available)
TODA is the sum of length of takeoff run available and length of clearway available. In case no clearway exists, TODA is same as TORA. TODA includes ground as well as air segments.
ASDA (Accelerate-Stop Distance Available)
It is defined as lenght of take off run available plus the length of Stopway. ASDA is important factor for determination of V1 speed. It 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.
LDA (Landing Distance Available)
LDA is the runway length declared available and suitable for landing an airplane.
Information on Clearway, Stopway, TORA, TODA, ASDA & LDA for different runways can be obtained from Aerodrome Information Publications, Jepessen Charts and RTOW charts.
ICAO document : http://www.icao.int/NACC/Documents/Meetings/2015/GREPECASPF2/GRPECASF2-P09.pdf