Table B-43. Helicopter Crash Frequency.

DOE-STD-3014-96

APPENDIX B

The next step is to determine the impact frequency from intentional overflight of

helicopters. First, determine the number of operations. Earlier in the problem this was

defined as 365/y (or 1/day). Next, get the effective area from Table B-34. The

helicopter crash frequency is shown in Table B-43.

TABLE B-43. Helicopter Crash Frequency.

Average

Number of

Crash

Length of

Frequency

Operations

Rate/Operation

Sq. Miles

Flight (mi)

Helicopter

365

2.5E-5

6.6E-4

3.3E-7

The next set of steps calculates the total impact frequency (see Section 5.3.3 of the

standard). The analyst begins by adding the near-airport and in-flight results for each

category/subcategory. The results are shown in Table B-44.

TABLE B-44. Total impact frequencies by category/subcategory.

Category/Subcategory

Impact Frequency (per year)

General Aviation

6.2E-6

Commercial Aviation Air Carrier

1.5E-7

Commercial Aviation Air Taxi

3.5E-7

Military Aviation Large Aircraft

6.4E-7

Military Aviation Small Aircraft

6.8E-7

Helicopters

3.3E-7

Total (all aircraft)

8.4E-6

Next, the analyst sums up the category/subcategory totals to find the total frequency of

aircraft impact into the facility. This equals 8.4E-6, so the facility does not pass the

impact frequency evaluation guideline in Section 4.2. Therefore, the analyst must

decide which categories to forward to the structural analyst.

B-48