JP 3-50 National Search and Rescue Manual Vol I - US Navy

Figure 5-36.
divides the circle into three equal triangles with one corner
of each triangle at datum. All search legs, crosslegs, and
the maximum track spacing are equal to the radius of the
circle.
b. The four-sector pattern has 90 degrees between
successive radii, and only two search legs (diameters) and one
crossleg (equal to 1.4 times search radius) are required to
complete the pattern. To obtain complete area coverage, the
pattern is rotated 45 degrees after completion of the first
pattern, and then run again.
2. Sector Single-Unit Radar (VSR) is used when a radar-equipped
marine craft takes station at the center of the pattern and
provides radar navigation assistance to one aircraft
completing a sector search pattern.
G. Contour Patterns (O) are used for search in mountainous and
hilly terrain. They are adaptable to underwater SRUs for searching
peaks on the ocean floor. Contour searches are covered in Chapter 8.
H. Flare Patterns (F) are used only at night. Detection of
survivors without visual aids is difficult at night. Parachute flares
increase the chance of detection only slightly and are effective mostly