Figure 13. Search Sector Size
b. Establish Upper and Lower Limits. Vertical search limits are helpful in detecting
aircraft. When searching and scanning for aircraft, do not limit your search too near the horizon
and miss higher flying aircraft, nor search too high above the horizon and miss lower flying
aircraft. Establish the search area 20 degrees above and 20 degrees below the horizon. This will
ensure that aircraft are detected within the search parameters.
One method of estimating 20 degrees is extend one hand straight in front of you with your fingers
fully spread. With your thumb in the air and your little finger pointed at the ground and touching
the apparent horizon, your thumb tip will be about 20 degrees above the horizon
(Figure 14).
Figure 14. One Method of Estimating 20 degrees
20
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