Background
Declared distances are specific lengths of runway that are published for aircraft operations, specifically when taking off or landing, and are defined for pilots to understand their allowable take-off and landing weights and speeds.
The declared distances for a runway comprise the Take-Off Run Available (TORA), Take-Off Distance Available (TODA), Accelerate-Stope Distance Available (ASDA), and Landing Distance Available (LDA).
Defining Each Runway Declared Distance
To define and calculate each declared distance, we must first look at what is meant by a clearway, stopway, and displaced threshold. Each definition has been taken from ICAO’s Annex 14:
- Clearway (CWY) – A defined rectangular area on the ground or water under the control of the appropriate authority selected or prepared as a suitable area over which an aeroplane may make a portion of its initial climb to a specified height.
- Stopway (SWY) – A defined rectangular area on the ground at the end of take-off run available prepared as a suitable area in which an aircraft can be stopped in the case of an abandoned take-off.
- Displaced threshold – A threshold not located at the extremity of a runway.
The definitions of each declared distance, also defined by ICAO, are presented below:
- TORA – The length of runway declared available and suitable for the ground run of an aircraft taking off.
- TODA – The length of TORA plus length of the CWY, if provided.
- ASDA – The length of TORA plus the length of the SWY, if provided.
- LDA – The length of the runway declared available and suitable for the ground run of an aircraft landing. (The length of the TORA minus the length of the displaced threshold).
An illustration of the declared distances taken from Annex 14 is shown in Figure 1 below.
Figure 1: Illustration of Declared Distances.
Dublin Airport Runway Declared Distances
The declared distances in metres for Runways 10/28 and 14/36 at Dublin Airport are presented in Table 1 below. The information has been taken from the Irish Aerodrome Information Publication (IAIP). 
Table 1: Dublin Airport Declared Distances.
Illustrations of each of the runway declared distances are presented in Figures 2 to 5 below. The figures show the runway in grey, stopway in blue, and clearway in green. All declared distances are illustrated for operations from left to right.
RWY 10
Figure 2: RWY 10 declared distances.
RWY 28
Figure 3: RWY 28 declared distances.
RWY 16
Figure 4: RWY 16 Declared Distances.
RWY 34
Figure 5: RWY 34 Declared Distances.
Conclusions
It is essential that a pilot is aware of the published runway declared distances as well as the operational requirements of their airplane to safely leave or arrive at an airport. It may seem intuitive that the entire length of the runway can be used for all operations however, as we’ve seen from the example of Dublin Airport, this is not always the case.
Pager Power
Pager Power uses runway declared distances to accurately construct Obstacle Limitation Surfaces to undertake Physical Safeguarding Assessments. Undertaking a physical safeguarding assessment is vital in understanding whether a building or wind developments can pose a physical collision risk for an airport. For more information please call us on 01787 319001.
References
[1]Brown, M., 2009. Reporting Declared Distances To Aeronautical Information Services. [online] Faa.gov. Available at: https://www.faa.gov/airports/airport_safety/certalerts/media/cert0905.pdf [Accessed 13 July 2020].
[2]ICAO, 2018. ICAO Annex 14 Volume 1 – Aerodromes – Aerodrome Design And Operations. [online] Available at: https://www.faa.gov/airports/airport_safety/certalerts/media/cert0905.pdf› bazl › icao-annex › an14_v1_cons [Accessed 13 July 2020]
[3]Irish Aviation Authority, 2020. IAIP. [online] Iaa.ie. Available at: https://www.faa.gov/airports/airport_safety/certalerts/media/cert0905.pdf [Accessed 13 July 2020].
