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22 lide with fixed or movable objects after departing the runway edge and possibly the RSA. The methodology used to assess risk during the airborne phase was the CRM. Although the CRM model was developed in the 1970s and the FAA has been improving these models since the 1990s, the original CRM can serve as a screening tool to evaluate the feasibility of submitting an MOS. The FAA has other tools to evaluate the need for further analysis if the risk estimated is within a feasible range. A summary of the CRM approach, variables, and models is provided in Appendix B. LandingâAirborne Phase Model It is recognized that running the CRM demands the avail- ability of specific software and the expertise to use it. To facili- tate the analysis and the application of the methodology, several CRM runs were made for common situations and different ADGs; however, when the analysis involves specific aircraft rather than an ADG, for the airport to obtain more accurate estimates of risk, the assessment should use direct results from the CRM analysis and specific conditions, if possible. Several CRM runs were made with obstacles located at var- ious separations from the runway centerline and along the run- way length. For Cat I, an obstacle clearance height (OCH) of 200 ft was used, and for Cat II an OCH of 100 ft was used. The ranges used were â300, 0, 1,500, 3,000, and 4,500 ft. Figures 16 and 17 illustrate the experiment run for several runway/taxiway separations. In Figure 16, only ranges of â300, 0, and 1,500 ft are shown. With the results from the CRM analysis, the maximum risk for each runway/taxiway separation was identified among the five locations along the parallel taxiway. The next step was to develop risk plots for wingtip separation versus risk in terms of accidents per number of operations. The process was repeated for each ADG, and risk plots were prepared for each group and instrument approach Cat 1 and 2. The approach to estimating risk using the plots presented in Appendix A may be viewed as conservative for the follow- ing reasons: ⢠Only the highest risk along the runway length was used for the estimate of collision risk. Figure 16. Plan view of CRM run experiment. Figure 17. Perspective view of CRM run experiment (not to scale).
