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

TABLE 5-10. Sweep Widths for Surface Vessel Radar (NM)
Sweep Width (NM))
Douglas Surface Vessel
Sea Radar System
Target Type State AN/SPS-64(V) AN/SPS-66
Small (20 feet or less)
fiberglass boats, without 0 to 1 1.4 0.8
radar reflector or 2 to 3 1.1 0
engine/metal equipment
Small (20 feet or less)
fiberglass boats, with 0 to 1 5.0 2.0
radar reflector or 2 to 3 1.6 0.4
engine/metal equipment
Medium to large vessels
(40 feet or over) with 0 to 2 13 9.5
significant amounts
of reflective material
a. For intermediate-size targets in sea states below 3,
the information from the SVR table must be interpolated. For
sea states greater than 3, sweep width should be estimated on
the basis of sea state and target characteristics.
b. When windy conditions cause heavy sea clutter, SVR
search patterns oriented with major search legs in the
crosswind direction and crosslegs in the downwind direction
provide the best radar coverage. However, sea conditions may
inhibit searching in this manner.
5. Sweep widths for Forward-Looking Airborne Radar (FLAR) can be
calculated using the values in Tables 5-11 and 5-11a.
a. Sweep widths for small targets in sea state 3 or
higher decrease rapidly to zero.
b. Detection range is more often limited by either
clutter or signal-to-noise ratio than by horizon distance.
c. AN/APS-127 searches should be conducted at lower
altitudes whenever flight operations permit, particularly when
seas are greater than two feet, because higher altitudes tend
to enhance sea return.
d. The AN/APS-127 provides a useful detection capability
for life rafts when the 10NM scale is used. The 20NM range
scale may degrade detection capability at each range interval
but the doubling of the range scale leads to a greater sweep
width. Either the 10 or 20NM range scale is effective against
24 to 43 foot boats.