Table of Contents
2 Background and Terminology,
3 Declared Distances
3.1 Take-Off RunAvailable(TORA)
3.2 Take-Off Distance Available (TODA)
3.3 Accelerate Stop Distance Available (ASDA)
3.4 Landing Distance Available (LDA)
4 Application and Publication of Declared Distances
5 Runway End Safety Area (RESA)
7 Appendix 1
8 Appendix 2
9 Appendix 3
9.1 List of Abbreviations
In a conventional air transport system, airports and aircraft are highly dependent on each other in providing service for their customers and passengers. Especially advances in the engine and airframe technology forced airports to plan, design, and construct facilities necessary to ensure that they were not left behind in full participation in a high growth industry. Nowadays international airports are progressively faced with huge aircraft with greatly increased wingspans carrying almost 900 people. These new circumstances affect airport layouts eminently. Beside the configuration of cargo and passenger terminals, geometric and structural design of pavements, including taxiways, exists and aprons, number and orientation of runways, the length of the runway is a main factor which has to match the improved parameters (Ashford/Mumayiz/Wright 2011, p. 74 ff.). Nevertheless, international airports operate with a wide range of present-day aircraft which have quite different requirements of the runway. At this point it is up to the airport owner to declare distances on the runway which are available for satisfying the takeoff runs and landings of airplanes. We know, the longer the runway the higher the costs for sure; but with the provision of declared distances the more and larger aircraft can be attracted by the airport especially for small airports with relatively short runways.
It is exactly the mentioned runway which plays a central role in the entire airport facility system. The runway has always been the most crucial point of all maneuvering areas where all takeoff and landing movements take place. It is proven that takeoff and landing phases are the most critical parts of all stages of a flight. They are demanding the highest skills from the crews and placing huge stresses and strains on the aircraft itself (Croucher 2007, p. 12-1). Therefore it is no wonder that events in which an aircraft veers off or overruns the runway surface during either takeoff or landing, so called runway excursions, are the most likeliest emergency situations. According to the Air Transport Safety Survey, runway excursions are the most common type of accident reported annually both in the European region and elsewhere in the world. 106 excursions with commercial and executive aircraft operations worldwide were recorded in 2012. That means there are at least two runway excursions each week worldwide (Air Transport News 2013, p. 13).
ICAO Aircraft Accident/Incident Data Reports (ADREP) have shown that aircraft undershooting or overrunning the runway during landing or takeoff suffer significant damage. To minimize such damage, it is considered necessary to provide structural measures or additional areas at and beyond the end of the runway or even surrounding the landing strip. Subsequently, provisions of declared distances and safety areas make an important contribution to preclude potentially hazards to aircraft and to protect passengers and people on the ground in case of an aircraft veers off or overruns the runway.
In the first two chapters I am going to explain the various kinds and differences of declared distances by explaining the relevant background and basic terminology with the help of illustrations. In the following I will briefly identify application areas of declared distances and how or rather why they have to be published for flight crews. Finally the paper concludes with a small insight in the field of safety areas in particular the Runway End Safety Area.
2 Background and Terminology
In applying declared distances and safety areas in airport design, it is helpful to understand the relationship between aircraft certification, aircraft operating rules, and airport data and design.
During the entire takeoff procedure the complex aircraft systems are running under full throttle. In this phase of flight various technical malfunctions, the recognition of a significant abnormality or an ATC instruction to stop the aircraft can occur that is forcing the pilot to abort the departure until reaching the calculated takeoff decision speed (V!). This speed is computed by the pilots in advance based on the airport data/design and can be understood as a "Go or No Go Decision". At speeds below Vi, the aircraft may be able to stop before the end of the runway. Once Vi has been exceeded, the takeoff must be continued even if an emergency occurs.
Additionally aircraft certification provides the aircraft's performance distances. They are based on the performance speeds/data of each individual aircraft established by the manufacturer and confirmed during certification testing for varying climatologically conditions, operating weights and much more. Typical performance distances are:
- Takeoff Run - The distance to accelerate from break release to lift off
- Takeoff Distance - The distance to accelerate from break release past lift off to start for takeoff climb
- Accelerate-Stop Distance - The distance to accelerate from break release to Vi and
then decelerate to a stop
- Landing Distance - The distance from the threshold to complete the approach, touchdown, and decelerate the approach.
All distances are published by the manufacture and internalized by the type-rated pilots. These distances, based on specific parameters mentioned above, are given and cannot be changed by the crew. To all distances a certain safety factor is included (FAA 2012, p. 57).
Now we are going into detail and I will define and explain the basic terms and acronyms which are from evident importance to understand the system of safety areas and declared distances. Basic definitions are given in Annex 14 and Aerodrome Design Manual (Doc 9157), both published by the International Civil Aviation Organization (ICAO).
As mentioned in the introduction, the length of the runway is from upmost importance and influences the aerodromes performance data decisively. The field length is determined not only on the basis of the aircraft's design but also by the safety regulations established by the responsible bodies of individual member countries of the ICAO. The actual runway length should always be adequate to meet the operational requirements of the airplanes for which the runway is intended. Furthermore, the length should be not less than the longest length determined by applying the corrections for local conditions to the operations and performance characteristics of the relevant aircraft (ICAO Annex 14, 3.1.6).
In some cases airport operators plan to extend the dimensions of the runway. Reasons can be varie- er aircraft. Often operators have an agenda to reach socio-economic goals or their intention is to improve the level of service; Or they simply try to improve safety. Whatever the reasons are, runway extension decisions can be very costly and complex (LPS Aviation 2007, p. 5).
In particular out of safety perspectives it can be absolutely worthwhile to increase the length of the runway. If you have a closer look on the accident statistics you will see that overrunning the end of the runway during takeoff and landing are one of the most common types of aircraft accidents. In this regard a useful alternative of extending the actual length of runway can be the so called Stopway (SWY). The SWY constructed at the end of runways as emergency space to slowly stop planes that overrun the runway to slowly stop a plane on a rejected takeoff.
According to ICAO Annex 14 SWY is defined as follows: "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."
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Image 1: Simplified Illustration of a Stopway [Own Illustration)
Nevertheless, if a SWY is established it must fulfill various conditions. According to the regulation of the respective aviation authority it must be able to support the weight of the largest aircraft able to use and shall be constructed with sufficient strength to support a decelerating aircraft in all weather conditions. Additionally, the aerodrome operator designates and commits to maintaining the area as stopway, including the appropriate lighting and marking shown in the image below (FAA 2000, p. 1).
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IMAGE 2: EXAMPLE OF THE PROPER MARKING OF A STOPWAY [FAA 2012, p. 93)
A second option to increase the length parameters of a runway is the establishment of a Clearway [CWY). A CWY is a nearly flat part on the ground or water and is not a paved part of the runway like the SWY is. It should be understood as a safety area beyond the runway end, which allows an airplane to fly over in low altitude after takeoff without the threat of getting endangered by any major obstacles. Generally it does not extend beyond the airport boundary. Again ICAO Annex 14 provides an official definition: "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." The image below depicts a simplified figure of the
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IMAGE 3: SIMPLIFIED ILLUSTRATION OF A CLEARWAY (OWN ILLUSTRATION)
Basically for large airports the application of SWY and CWY does not make any sense in most cases because they do have a relative long runway anyway. However, for example for smaller regional airports with limited financial resources, which are in addition short of space on the airside area, the establishment of a SWY/CWY can be a useful option. As a result airport planners can benefit from both alternatives. It is frequently advantageous to establish a clearway because it saves full strength runway without penalizing the operational usage. More precisely a clearway increases the allowable aircraft operating takeoff weight without increasing the length of the runway (Ashford/M umayiz/Wright 2011, p. 90; FAA 2012, p. 65). Unfortunately most ICAO recommendations concerning SWY and CWY published in Annex 14 are ambiguous and are not uniformly applied worldwide. Whenever a crew is in doubt about the quality of a SWY/CWY, consideration in performance optimization tools may be inappropriate (Bos 2013, p. 1). Nevertheless, whenever a SWY/CWY is provided, the stopway length and the declared distances shall be provided in the airport/facility directory and in the aeronautical information publication (AIP) for international airports for each operational direction (ICAO Doc 9157, 3.4.2). A practical example will follow in the appendix.
Before finally entering the main subject of declared distances, I need to make a short explanation of the term "Displaced Threshold". The landing threshold marks the beginning of that portion of the runway usable for landing and is usually located at the beginning of the runway. However, displacement of the landing threshold may be required when an object that obstructs the airspace required for landing aircraft is beyond the airport owner's power to remove, relocate or lower. Thresholds may also be displaced for environmental considerations, such as noise abatement, or to provide additional safety space. Hence, the displacement of the threshold shortens the usable runway length for landing, while not affecting the distance of the runway available for departing aircraft (FAA 2012, p. 52). Whenever a displaced threshold is encountered it must be identified, classified, and documented similarly to a runway end.
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Image 4: Simplified Illustration of a Displaced Threshold (Own Illustration)
- ISBN (eBook)
- ISBN (Buch)
- 1.6 MB
- Institution / Hochschule
- Technische Hochschule Wildau, ehem. Technische Fachhochschule Wildau – Wildau Institute of Technology
- Air Traffic Control ATC TORA TODA ASDA LDA RESA Declared Distances Safety Areas ATM Air Traffic Management Landing Distance Available Runway End Safety Area Takeoff Distance