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12 Airfield Lateral Deviation Studies During the course of study, an attempt was made to obtain data on extreme lateral aircraft deviations for runways, taxi- ways, and taxilanes. Also, information was gathered from previous studies and lateral deviation data and models to determine the best alternatives to use in the approach and the methodology to evaluate airfield separations. Appendix C provides a summary of this literature review. Ensuing sections of this report provide summaries of data collected in this research and describe previous studies evalu- ating the magnitude of lateral aircraft deviations during airfield operations as well as the attempts to model the probability distributions of these lateral deviations. A major consideration is random lateral deviations of air- craft during runway, taxiway, and taxilane operations. The probability distribution of such deviations relative to the centerline/guideline of runways and taxiways is crucial to assessing the adequacy of existing separation/clearance dis- tances for safe and regular operation of aircraft, both on straight portions and on taxiway curves. The following fac- tors may impact those deviations (Eddowes, Hancox, and MacInnes, 2001): ⢠Quality of aircraft nose wheel guidelines (marking and lighting) ⢠Quality of signs ⢠Visibility conditions ⢠Level of light (day or night) ⢠Surface condition (dry, wet, contaminated by snow/ice, rubber, etc.) ⢠Approach speed and touchdown location ⢠Taxi speed ⢠Pilotâs attention ⢠Pilotâs technique during landing ⢠Stability of approach ⢠Pilotâs technique on negotiation turns ⢠Wind effects (cross-wind) ⢠Aircraft handling characteristics ⢠Mechanical failures In the 1970s, the FAA and the U.S. Army Corps of Engineers (USACE) carried out substantial studies on lateral distribu- tion of aircraft traffic on runways and taxiways (Brown and Thompson, 1973; HoSang, 1975). More recently, Cohen-Nir and Marchi (2003), the FAA, and Boeing (Scholz, 2003a and 2003b) performed statistical analyses of taxiway deviations for large aircraft at John F. Kennedy International Airport (JFK) and Ted Stevens Anchorage International Airport (ANC). Veer-Off Accidents and Incidents Both the FAA and ICAO address the probability of aircraft veer-offs in their rationale for runway/taxiway separations. ICAO (2004) emphasizes that runway separation issues are supported by local airport experience in terms of identifying causes and accident factors specific to the local environment. No less important is the enormous variety and complexity of accident factors for collision risk. One of the subtasks of this project was to carry out a func- tional hazard analysis (FHA) for aircraft veer-offs based on information gathered in the literature review. The objective of this subtask was to identify relevant factors associated with such events to support the data collection effort for accidents and incidents. The research team collected information that could be used in the modeling process, particularly data on causal factors and aircraft location. Identifying the most rel- evant factors causing or contributing to such events also was part of the modeling process. An FHA is a formal and systematic process for the identifi- cation of hazards associated with an activity that is typically employed to support risk assessment and management. An FHA is often conducted in the form of a brainstorming work- shop involving a multi-disciplinary team that could include pilots, air-traffic controllers, airside operations personnel, and C H A P T E R 3 Data for Modeling Aircraft Deviations