Impact Frequency from Nonairport Operations.

DOE-STD-3014-96

Step 3. Given the orthonormal distance of the facility from each flight source, obtain the

generic aircraft crash location probability per square mile, i.e., f(x,y), for takeoff and

landing for each aircraft category/subcategory. This information is included in Appendix B

as Tables B-2 through B-13. If the orthonormal distance of a facility falls outside the

boundaries of these tables, the corresponding f(x,y) is assumed to be zero (a

noncontributor).

Step 4. Obtain the aircraft takeoff and landing crash rates, P, for each aircraft category

or subcategory. This information is provided in Table B-1 of Appendix B.

Step 5. Calculate the effective area, A, for each aircraft category or subcategory. The

calculation of the effective area consists of two components: the aircraft can crash into

the structure either by skidding or by flying directly into it. To calculate the effective area,

assume that the aircraft skids or flies into the structure in the direction that produces the

largest area, i.e., crashing in a direction perpendicular to the largest diagonal of the

building. The formula for calculating the skid- and fly-in areas of an aircraft crashing into

a facility are provided as Equations B-3 through B-5 in Section B.4 of Appendix B. The

effective area is a function of the cotangent of the impact angle, wingspan, and skid

distance of the crashing aircraft. Values of these parameters are given in Section B.4 of

Appendix B.

Step 6. Multiply the values for N, P, f(x,y), and A for each combination of flight source,

flight phase, and aircraft category/subcategory. Sum over flight sources and flight phases

to calculate an impact frequency for each aircraft category/subcategory. (Do not sum the

categories yet; this will be included in a later step.)

Impact Frequency from Nonairport Operations. Even though the expected

5.3.2

frequency of aircraft crashes into a facility due to mishaps occurring during the in-

flight phase of operation, is expected to be lower than the frequency associated

with airport operations, the expected frequency cannot be shown to be a

noncontributor to the overall frequency for all facilities. Thus, nonairport

operations must be considered in the impact frequency analysis.