Bird strike risk assessment at commercial airports: sub-model development accounting for strike occurrence and severity with strike contributory factors

The collisions between birds and airplanes, or bird strikes, pose a substantial safety and financial threat to the public through issues such as delays, airplane damage, passenger injuries or deaths, and environmental impacts. Current records indicate that an average of 19 bird strikes are reported each day in the United States, and the number has been increasing very quickly over recent years. The reported bird strikes have resulted in a financial loss of more than $600 million for commercial aviation in the United States and $1.2-1.5 billion worldwide. Despite the number and severity, quantifications of bird strike contributory factors have been quite limited because of the absence of data, especially bird movement data on airfields. The goal of this study is to provide additional insight into this important problem by combining a number of databases, including the newly available bird movement data collected by the avian radar, the FAA wildlife strike database, airport operations, airplane characteristics and meteorological data. Statistical models were developed to quantitatively evaluate the factors that contribute to bird strike occurrence and severity. The study of bird strike occurrence is composed of two sub-studies. One sub-study investigated the impacts of bird and airplane movement on bird strike occurrence. This study was carried out at Seattle Tacoma International Airport. Logistic regression was applied and the results showed that bird strike occurrence was positively related to both bird density and airplane movement frequency. The other sub-study analyzed the effects of meteorological variables (e.g., temperature) on bird strike occurrence also with logistic regression. Ten years of meteorological data collected from six U.S. major airports was used and the results indicated that temperature and precipitation were major factors that have significant effects on bird strike occurrence at most of these airports, while other factors including wind speed, visibility and pressure, only have effects at certain airports. The study of bird strike severity evaluated the effects of a set of variables, such as airplane mass, engine type, number of engines, altitude, bird size, and strike position of an airplane. Multinomial regression model was used to quantitatively analyze the impacts that such variables pose on three severity categories: no damage, minor damage and serious damage. Based on the data collected from commercial airports in the United States, the results indicated that small airplanes, single engine, fast flight speed, takeoff, large and flocking birds, strikes occurring at engine, wing, tail and light increased the propensity toward both serious and minor damage. Variables such as landing, warned status, and strikes occurring at nose, propeller and fuselage increased the chance of no damage. The overall study provides a series of empirical and methodological assessments to examine the effects of bird strike contributory factors on strike occurrence and severity. Logistic and multinomial regression models were applied respectively and were estimated with full information maximum likelihood to yield statistically efficient results. The findings provide quantitative evidence demonstrating factors that are relevant, and the significance of their impacts. The results not only support potential changes in airport bird hazard management and airplane operations, but also suggest improvements in engine and airframe design for safety considerations. The study also highlights the importance of managing accurate bird strike reports and applying new statistical approaches in the future as more data becomes available