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4 Finally, Chapter 7 describes the major conclusions and rec- that may occur in those locations. Two of those sections are ommendations from this study. It also explains major achieve- located on each runway end and include the RSA portion im- ments and limitations. mediately before the arrival thresholds and beyond the depar- ture end of the runway. These are the sections that help mit- igate consequences of aircraft overruns and undershoots. The Project Goals third RSA section is lateral to the runway and extends over the The ultimate objective of this research was to develop a risk runway length on both sides of the runway. This is the area assessment tool that can be used to evaluate alternatives for that can help mitigate the severity of aircraft veer-off incidents. RSA improvements, with a capability to account for the use For the RSA sections located laterally to the runway, im- of EMAS, declared distances, the presence of obstacles, spe- provements can be made by removing obstacles and preparing cific operations, weather, and runway conditions. the area according to RSA standards to increase the runway New models were developed, and the capability to evalu- object free area (ROFA) width. In some cases this may be nec- ate risk for veer-off events was added to the approach pre- essary to introduce the operation of larger aircraft to increase sented in ACRP Report 3. Five sets of models were developed in capacity; however, they may be restrained to increase the ex- this study: landing overruns, landing veer-offs, landing under- isting runway separation distances to accommodate the larger shoots, takeoff veer-offs, and takeoff overruns. Each set includes airplane design group (ADG). three models: incident frequency, stop/touchdown location, There are four basic alternatives available to improve an and consequences. RSA when it does not meet the standards: The following were the specific goals that were achieved for ACRP Project 4-08: Extend the RSA laterally and longitudinally. Modify or relocate the runway to expand the RSA. 1. Update the ACRP Report 3 accident/incident database to Implement declared distances by reducing the available incorporate aircraft overrun and undershoot accidents and runway distances and extending the RSA section adjacent incidents occurring after 2006. to the runway ends. 2. Collect data on aircraft runway veer-off accidents and in- Use arresting systems to obtain a level of safety similar to cidents and integrate these data into the existing database. that provided by the standard RSA. 3. Develop risk models for frequency and location for each type of incident: landing overruns (LDOR); landing under- Any combination of such alternatives is also possible, and shoots (LDUS); landing veer-offs (LDVO), takeoff overruns the methodology presented in this report has the capability (TOOR), and takeoff veer-offs (TOVO). to analyze any such combinations. Each of these alternatives 4. Develop a practical approach to assess the impact of run- has advantages and disadvantages that are specific to each sit- way distance available on the probability of overruns, under- uation and that need to be assessed, as described in ensuing shoots, and veer-offs. sections of this report. 5. Develop a practical approach to assess risk and the impact It is important to note that airport operators can take addi- of using EMAS as an alternative to standard RSAs, or to tional actions to mitigate the probability of aircraft overruns, use declared distances and evaluate the safety impact of undershoots, and veer-offs. Some possible alternatives may reduced runway distance available. include the following: 6. Develop a practical approach to model incident conse- quences based on existing conditions and the presence of Improve skid resistance and reduce undulations of runway obstacles inside or in the vicinity of the RSA. surface. 7. Develop user-friendly software that incorporates the Monitor runway friction level to determine need to close methodology and models developed as a practical tool that the runway (e.g., ice conditions) and time for maintenance airport stakeholders may use to evaluate RSA alternatives. (e.g., rubber removal). 8. Field test the software developed. Ensure accurate weather information and runway surface 9. Validate the new tool based on data gathered according to conditions are available to flight crews. an airport survey plan. Improve airport capability to detect unusual weather con- ditions (e.g., wind shear). RSA Improvement Alternatives Minimize the presence of obstacles in the vicinity of RSAs. Upgrade visual and instrument landing aids to improve ac- General Considerations curacy of approach path. To facilitate understanding the role of an RSA, it can be di- Coordinate operational restrictions with airlines and air traf- vided into three sections as a function of the types of incidents fic control (ATC) when adverse weather conditions arise.

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5 Publish RSA provision in the Aeronautical Information Pub- Existing RSA lication when RSA's cannot comply with standards. Although these actions can decrease the probability of un- desirable events, it is not possible to measure the impact of these risk mitigation actions on the total airport risk of seri- Improved RSA ous aircraft overruns, undershoots, and veer-offs. This study introduces a risk-based methodology for quan- 1000 ft titative evaluation of any of the alternatives or combinations of RSA improvement alternatives identified in FAA Order Figure 2. Relocating the runway. 5200.8 (1999). These alternatives are described below. necessary to implement declared distances to accommodate a Extend the RSA larger RSA. Figure 3 shows an example to extend the RSA using An example of extending the RSA is shown in Figure 1. In this alternative. this case, the RSA adjacent to the right runway end and the This is a fast and low cost alternative for the airport opera- lateral area originally did not comply with the standard. tor; however, it may impact airport capacity, reduce payloads, This is a straightforward solution to improve an RSA and and/or degrade the level of safety under specific situations, is used to extend it to the runway ends or the lateral sections. which may lead to long-term consequences to the airport. In However, this alternative is not always feasible due to phys- the example provided, the runway was reduced to accommo- ical, environmental, or other constraints involved with date a larger RSA by reducing the landing distance available. implementation. Use of Arresting Systems Modify or Relocate the Runway When a full RSA cannot be achieved, the airport may use In Figure 2, the runway was relocated to the left to obtain a bed of lightweight concrete that is crushed under the wheels a standard RSA of 1000 ft in length. The relocation also may of a stray aircraft, causing energy from its forward motion to involve the change of runway direction. be absorbed, to bring the aircraft to a stop within a shorter Similar to the previous alternative, this solution may involve distance. A standard EMAS bed can reduce what would nor- very high costs, particularly if changing the runway direction mally be a 1000-ft RSA to 600 ft, or even less if the land is is necessary. In this case, a new runway must be constructed not available, depending upon the aircraft types using the to replace the existing one. For the example shown, to keep runway. Figure 4 presents an example of RSA improvement the distance available for landing, it is necessary to extend the using EMAS. runway to the left. This is an alternative that only became available in recent years and provides a feasible solution, particularly for land- locked runways. The major disadvantages are the high initial Implement Declared Distances cost, maintenance costs, the need to replace the bed when Declared distances are a means of obtaining a standard used, the need to periodically replace the bed due to natural safety area by reducing the usable runway length. When the deterioration, and it still requires some land area to be avail- RSA cannot be extended or the runway relocated, it may be able for installation. Existing RSA Existing RSA Improved RSA Improved RSA 1000 ft Figure 1. Extending the RSA. Figure 3. Using declared distances.

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6 Existing RSA EMAS Bed Improved RSA Figure 4. Using EMAS.