Table B-17. Values of the mean of the cotangent of the impact angle (cot ).

DOE-STD-3014-96

APPENDIX B

TABLE B-17. Values of the mean of the cotangent of the impact angle (cot ).

Military Aviation

Aircraft

Commercial

General

Helicopters

Large Aircraft

Small Aircraft

Category

Aviation

Helicopters

Large Aircraft

Small Aircraft

Takeoff

Landing

Takeoff

Landing

Mean Skid

1440

780

368

246

447

Distance, ft

In calculating an effective area, the analyst needs to be cognizant of the "critical areas"

of the facility. Critical areas are locations in a facility that contain hazardous material

and/or locations that, once impacted by a crash, can lead to cascading failures, e.g., a

fire, collapse, and/or explosion that would impact the hazardous material. This

knowledge is important for reducing the unnecessary conservatism that is likely to be

introduced if the facility's dimensions are used blindly. For example, if the critical area

dimensions are small fractions of the overall facility dimensions, this must be reflected

in the analysis. In addition, the analyst needs to consider the facility's layout and its

location in relation to other facilities when determining the facility input parameters.

Information about critical areas and potential aircraft heading angles may eliminate or

change the need for further analysis. Otherwise, the conservatism in the analysis

might unnecessarily overburden the evaluations.

In addition, there may exist conditions and physical attributes that could affect the

evaluation of the effective target areas. For example, there could be nearby barriers

that have sufficient structural integrity to resist impact from the categories (or

subcategories) of aircraft under investigation. Examples of barriers are robust

B-29