TM 1-1510-262-10
b. Fahrenheit to Celsius Temperature Conversion. Convert reported ield temperatures at the departure and
destination airports from Fahrenheit to Celsius using the Fahrenheit to Celsius Temperature Conversion graph (Fig.
7-9). Enter the chart at the appropriate value on the F scale, read up to the reference line and left to the corre-
sponding value in C.
Billings-Logan International 59F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C
Natrona County International 68F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20C
c. Pressure Altitude. To determine the approximate pressure altitudes at origin and destination airports, add
1000 feet to ield elevation for each 1.00 in. Hg that the reported altimeter setting value is below 29.92 in. Hg, and
subtract 1000 feet for each 1.00 in. Hg above 29.92 in. Hg. Always subtract 1000 feet for each 1.00 in. Hg above
29.92 in. Hg, then multiply the answer by 1000 to ind the difference in feet between ield elevation and pressure
altitude.
Pressure Altitude at BIL:
29.92
-30.07
-0.15
-0.15 x 1000 feet = -150 feet
Field Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3649 feet
Pressure Altitude Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -150 feet
Field Pressure Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3499 feet
Pressure Altitude at CPR:
29.92
-29.27
+0.65
0.65 x 1000 feet = 650 feet
Field Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5348 feet
Pressure Altitude Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +650 feet
Field Pressure Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5998 feet
d. Wind Components. Determine the headwind (tailwind) and crosswind component for the selected runway.
Compute the angle between the reported wind at Billings-Logan International of 290 and the selected runway head-
ing of 340 to be 50. Locate the line for 50 angle between wind direction and light path on the graph. Trace along
the 50 line and locate the reported wind speed of 15 knots (the point midway between the 10 and 20 knot wind
speed lines). Read left to obtain the headwind component and down to obtain the crosswind component.
Headwind Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 knots
Crosswind Component
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 knots
7-13
