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Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules
TABLE 5VARIABLE DEFINITIONS AND CONSTANT VALUES USED IN POLAR BEAR HARASSMENT ESTIMATES FOR WINTER
AND SUMMER AIRCRAFT ACTIVITIES ON THE COAST OF THE NORTH SLOPE OF ALASKAContinued Variable DpLT
tLT
DpTR
tTR
x Bes Bi ac ai eco eci eio eii ta Bt
Definition
Value
proportion of the day landing/take-off areas are impacted by aircraft activities.
amount of time an aircraft is impacting landing/take-off areas within a day
proportion of the day traveling areas are impacted by aircraft activities
amount of time an aircraft is impacting traveling areas
number of 3.22-km 2-mi segments within each traveling area
bears encountered in an area of interest for the entire season
bears impacted by aircraft activities
coastal exposure area
inland exposure area
coastal open-water season bear-encounter rate in bears/season
coastal ice season bear-encounter rate in bears/season
inland open-water season bear-encounter rate in bears/season
inland ice season bear-encounter rate in bears/season
aircraft harassment rate
number of estimated level B harassments

The number of times each flight path was flown i.e., flight frequency was determined from the application. We used the description combined with the
varies by flight.
10 minutes per flight.
varies by flight.
1.5 minutes per 3.22 km 2 mi segment per flight.
varies by flight.
varies by flight.
varies by flight.
1,610 m 1 mi.
1,610 m 1 mi.
3.45 bears/km2/season.
0.118 bears/km2/season.
0.0116 bears/km2/season.
0.0104 bears/km2/season.
0.23.
varies by flight.

approximate number of weeks and months within the open-water season and the ice season to determine the total number of flights per season for each
year f. We then used flight frequency and number of days per season ds to calculate the seasonal proportion of flights Sp; Equation 6.

f sp -- ds Equation 6
After we determined the seasonal proportion of flights, we estimated the amount of time an aircraft would be impacting the landing/take-off areas within a day tLT. Assuming an aircraft is not landing at the same time another is taking off from the same airstrip, we
estimated the amount of time an aircraft would be present within the landing or take-off zone would be tLT = 10 minutes.
We then calculated how many minutes within a day an aircraft would be impacting an area and divided by the number of minutes within a 24-hour
period 1,440 minutes. This determined the proportion of the day in which a landing/take-off area is impacted by an aircraft for each season DpLT; Equation 7.

Equation 7

=

Sp
travel area in a day and divided by the number of minutes in a 24-hour period.
This calculation determined the proportion of the day in which an aircraft would impact an area while traveling during each season DpTR;
Equation 8.

trn X
1440
Equation 8

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DpTR

slower flights at lower altitudes, such as summer cleanup activities and determined it would take approximately 1.5 minutes. We then determined how many 3.22-km 2-mi segments are present along each traveling path x.
We determined the total number of minutes an aircraft would be impacting any 3.22-km 2-mi segment along the
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jbell on DSKJLSW7X2PROD with PROPOSALS2

To estimate the amount of time an aircraft would be impacting the travel areas tTR, we calculated the minimum amount of time it would take for an aircraft to travel the maximum exposure area at any given time, 3.22 km 2.00
mi. We made this estimate using average aircraft speeds at altitudes less than 305 m 1,000 ft to account for