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20 CHAPTER 3 Findings and Applications Database Summary Statistics investigation report may describe high approach speed and long touchdown as causal factors, but the report described This section provides a statistical description of the data the runway surface as wet. Although the latter was not con- gathered in this study and included in the ACRP 4-01 acci- sidered a relevant factor in the investigation, the anomaly was dent and incident database. The final database incorporates present and is included in the summary statistics that follow. 459 accidents and incidents. Figure 8 depicts the distribution The anomalies were divided into six different categories to of events by type of accident and incident (LDOR, LDUS, or aid in understanding the factors leading to aircraft overrun TOOR). and undershoot events: Proportionally, there have been more LDOR than LDUS and TOOR, as shown in Figure 9. The numbers of LDUS and Aircraft System Fault (SysF); TOOR are similar. Wildlife Hazards (WH); Although some events prior to 1982 were included in the Weather Conditions (W); study, the majority of cases date from 1982 to 2006. The dis- Human Errors (H); tribution of incidents and accidents is variable along the Runway Surface Conditions (R); and period data was collected. However, in the average (from Approach/Takeoff Procedures (AT). 1984 to 2004), the number of reported accidents and inci- dents was similar and averages 18 events per year (9 accidents Several anomalies within each of these categories may be and 9 incidents). Part of the reduction observed for 2005 to present during accidents and incidents. The majority of these 2007 is due to the unavailability of the reports when the data anomalies were taken from the list of causal and contributing for this study were collected. For many events during this factors described in the investigation reports. In a few cases, period, either the reports had not been completed or they even when not listed in the report, if an additional anomaly were not yet available in electronic format. Figure 10 sum- was identified, it was included in this analysis. For example, marizes the number of events per year. some investigation reports did not describe the wet runway as a causal or contributing factor to the accident, but rain during touch down on the runway was listed, and wet runway Summary of Anomalies Associated was included in the analysis. with Accidents and Incidents The complete list of anomalies within each of the above An FHA was conducted during the initial stages of this categories and used in this study is shown in Table 4. study to identify the relevant factors associated with aircraft Figure 11 depicts the distribution by category for landing overrun and undershoot events so that data on these param- overruns. In this case, anomalies are mostly related to weather, eters could be gathered and included in the accident database human error, runway conditions, and approach procedures. and be used for developing risk models. Figure 12 shows the frequency of anomalies by the category The majority of investigation reports describe causal and for undershoots. Similarly to landing overruns, the anomalies contributing factors to accidents but in general these are not are mostly related to weather, human error, runway condi- reported for incidents. In addition, certain factors not de- tions, and approach procedures. Except for runway conditions, scribed as causal or contributing factors in the accident are the incidence of anomalies was higher for the accidents under relevant to the present study. For example, a runway overrun the predominant categories.