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measures (e.g., restricting the wingspan of taxiing aircraft, using centerline lights) or to evaluate the expected number of years for one collision event based on the volume of operations in the taxiway. For smaller airports with lower volumes of traffic, an acci- dent may be expected to occur less than once every 100 years, and this condition is classified as extremely improbable. In this case, the risk may be considered acceptable according to the criteria suggested by the FAA. Section 3âTaxilane to Taxilane Procedure to Estimate Risk of Collision 1. Identify the taxilanes and the centerline separation to be evaluated. 2. Identify the ADG for analysis or the types of aircraft that will be using each taxilane. It is possible that each taxilane is assigned to a different ADG or specific aircraft. 3. If the assessment is for a specific ADG, the simplified col- lision risk plots can be used based only on the taxilane centerline separations (Figures AA-15 to AA-20). 4. If the risk assessment involves specific aircraft or two dif- ferent types of aircraft, the wingtip separation plot in Fig- ure AA-21 should be used, and, in this case, the following steps will be required: a. Place both aircraft at the centerlines of the parallel tax- ilanes (see Figure A-8). b. Calculate the wingtip clearance for this situation: where WD is the distance between wingtips of the two aircraft when both are positioned at the centerline of the taxilanes, CS is the centerline separation between the parallel taxilanes, WS1 is the wingspan for the first aircraft, and WS2 is the wingspan for the second aircraft. WD CS WS WS= â +( )1 2 2 3( ) A-7 Figure A-6. Example of analysis for taxiway/object separation. 68 70 72 74 76 78 80 82 84 86 Taxiway Centerline to Object Separation (ft) ADG III Standard = 93 ft 1.E-10 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 R is k of C ol lis io n pe r O pe ra tio n Figure A-7. Example of analysis for taxiway/object separation (ADG III).
