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2Background Introduction Accident statistics show that from 1959 to 2011, 53% of the worldâs fatal commercial jet aircraft accidents occurred dur- ing landing and takeoff. These accidents accounted for 47% of all onboard fatalities (Boeing, 2012). Most of the aircraft accidents that occurred on or in the immediate vicinity of the runway were the result of undershoots, overruns, or veer-offs. The worldwide data for accidents and incidents from 1982 to 2008 collected for the ACRP Report 50: Improved Models for Risk Assessment of Runway Safety Areas showed that almost 50% of the events that have involved aircraft in RSAs were lateral runway excursions (veer-offs). Although in many cases the causal factors involve some type of human error, the conditions at the airport may be an important contributing factor that may affect the severity of the accidents. In an attempt to mitigate the severity of these accidents, the FAA developed standards for RSAs in the 1960s. The RSA is a graded and obstacle-free, rectangular-shaped area surrounding the runway that is âprepared or suitable for reducing the risk of damage to aircraft in the event of an undershoot, overshoot, or excursion from the runwayâ (FAA - AC 150/5300-13A, 2012). By reducing the chance of damage to the aircraft, the RSA also reduces the chances of death or injury to the occupants of an aircraft that is involved in a runway undershoot, over- run, or veer-off. RSAs have resulted in many potentially cata- strophic accidents becoming minor incidents. The rectangular dimensions of the RSA are dependent on the type and size of aircraft using the runway. To meet aviationâs continuous growth, airlines are operating larger aircraft with greater seating capacity. However, for many airports, airfield configurations were established many years ago and it is impracticable to meet the current RSA standards that have been established for these larger aircraft. The question arises as to what is the risk if these larger aircraft are allowed to operate in these airports with non-standard RSA dimensions. Currently there are no approved methodologies for assessing these risks and each situation is considered separately. Another issue that has challenged the aviation industry, particularly airport planners, is how much risk is associated with the presence of certain obstacles inside the RSA. Although most navigational aids (NAVAIDs) are mounted on frangible structures, some of those larger structures may cause damage to aircraft, such as glideslope antennas, runway visual range (RVR) masts, or VHF Omnidirectional Range (VOR) structures. A queue of aircraft waiting for takeoff on a parallel taxiway, rough terrain, drainage structures, and other obstacles may also be present in the vicinity of runways and may represent hazards to aircraft that veer off the runway. A tool to quantitatively estimate the risk of aircraft veering off runways and assess risk of aircraft operations under spe- cific conditions in a uniform manner will be very beneficial to airport operators and governmental agencies. The proposed approach is based on ACRP Report 50 and includes the factors that impact the level of risk for airport operations. This approach also provides a rational probabilistic methodology for the analysis of areas contiguous to the sides of the runway. The approach is based on data collected from accidents and incidents for the past 30 years. The analysis also utilizes historical data from the specific airport being evalu- ated. This allows the user to take into consideration particular operational conditions to which aircraft are subject to at the airport, as well as the actual RSA conditions in terms of dimen- sions, configuration, type of terrain, and existing obstacles. Despite the advances achieved with ACRP Report 50, the veer-off models developed for that project have some limita- tions, particularly in addressing the probability distributions of wreckage location for veer-off events over the length of the runway. This project further enhances the models described in ACRP Report 50 by considering adjusted (normalized) loca- tion data, as well as veer-off location relative to the begin- ning of the runway. Such factors were not included within the scope of the previous work. The location models were integrated into the analysis meth- odology and software with the capability of assessing RSA lat- eral areas, the areas contiguous to the longitudinal sides of the C H A P T E R 1
3 runway. The analysis was validated and took into consideration the RSA boundaries and existing obstacles within the existing or proposed RSA. This report summarizes the tasks, results, conclusions, and recommendations for the entire study. In addition, a software tool is included that may be utilized by the industry to assess risk associated with the lateral portions of the RSA. Project Objectives This project was aimed at identifying the subareas of the RSA where runway veer-offs are most likely to occur and develop quantitative analysis capability to evaluate the risk of runway veer-offs. Three goals were set to achieve this objective: ⢠Identify the probability of an aircraft that veers off the runway traversing various areas that are contiguous to the sides of the runway and determine how obstacles located within these areas may impact risk. ⢠Develop quantitative analysis capability and software tool to evaluate the risk of runway veer-offs and the probability dis- tribution of veer-off locations in the vicinity of the runway. ⢠Identify deficiencies in data availability to characterize the location distributions and make suggestions for future improvements to the models developed in this study.
