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12 Location Distribution for TOVO Events Aircraft Data 20 18 One of the project goals was to incorporate a factor in the models to account for the impact of aircraft performance and 16 available runway length on probability of incidents. When the 14 distance available is close to the distance required, the safety # of Events 12 margin is smaller during the aircraft landing or takeoff, and 10 the likelihood is greater that an overrun or veer-off will occur. 8 Compared to the ACRP Report 3 study, two new factors were 6 included in the improved models: the runway distance avail- 4 able for the operation (takeoff or landing) and the aircraft run- 2 way distance required under the operation conditions. The 0 runway available and required distances were gathered or esti- 0 0 0 0 50 0 e 0 0 0 0 mated for each accident, incident, and normal operation, ac- 30 35 40 45 50 or 10 15 20 25 M Distance from Runway Edge (ft) cording to the procedures described in ensuing sections. The parameter introduced in the frequency models was the loga- Figure 14. Location distribution for takeoff veer-offs. rithm of the ratio between the distance required and the dis- tance available, to address the interaction between the two pa- rameters. When the criticality factor is close to zero, the ratio deviated less than 175 feet from the runway edge. In 85% of between the required and available distance is close to one. the events, the aircraft was within 250 feet of the runway edge. Aircraft dimensions and performance data were gathered from various sources, including aircraft manufacturers' web- Normal Operations Data sites and other databases: Another key approach in this study was the use of NOD for FAA Aircraft Characteristics Database. probability modeling. In the absence of information on risk Source: FAA exposure, even though the occurrence of a factor (e.g., contam- Website: ( inated runway) could be identified as a contributor to many aircraft_char_database/) accidents, it is impossible to know how critical the factor is, Eurocontrol Aircraft Performance Database V2.0 since many other flights may have experienced the factor with- out incidents. With NOD, the number of operations that ex- Source: Eurocontrol perience the factor benignly, singly, and in combination can Website: ( FAA Aircraft Situation Display to Industry (ASDI)--Aircraft be calculated; risk ratios can be generated; and the impor- tance of risk factors can be quantified. This assessment may Types. allow the prioritization of resource allocation for safety im- Source: FAA provement (Enders et al. 1996). Website: ( The same NOD used in the ACRP Report 3 study was used in types.txt). Boeing Airplane Characteristics for Airport Planning. this study. The data were complemented with information for GA aircraft with MTOW lower than 12,500 lb and higher than Source: The Boeing Company 6,000 lb. The NOD database comprises a large and representa- Website: tive sample of disaggregate U.S. NOD covering a range of risk plan_manuals.html factors, allowing their criticality to be quantified. The data and Airbus Airplane Characteristics for Airport Planning. the information on U.S. incidents and accidents were used as a Source: Airbus Industrie sample to develop the frequency models only. A small sample Website: & Mainte- of the NOD used in this study is presented in Appendix C. nance/Technical data/Aircraft Characteristics Incorporating this risk exposure information into the acci- Embraer Aircraft Characteristics for Airport Planning. dent frequency model enhances its predictive power and pro- Source: Embraer vides the basis for formulating more risk-sensitive and respon- Website: sive RSA policies. Accident frequency models need no longer english/content/aeronaves/ rely on simple crash rates based on just aircraft, engine, or op- eration type. As discussed in the following pages, factors pre- Aircraft performance data used to develop the probability viously ignored by airport risk assessments and RSA regulations models also were incorporated into the analysis software. A are accounted for using the models developed in this study. summary of the aircraft database is presented in Appendix D.