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

SRUs are dispatched next. Supplementary SRUs may be requested from
other activities.
C. If sufficient SRUs are not available, compromises should be
made to develop an attainable search plan. These compromises may
involve reduction of the search area, increased track spacing, or the
use of less desirable SRUs.
532 Search Time Available
A. The amount of search time available (T) is of paramount
importance. Since survival rates normally decrease with time, the SMC
is always working against the clock. Limited time available for search
may require a rapid search rate at the expense of area searched or POD.
Two major controlling factors for computing search time available are
SRU endurance and amount of daylight available.
B. Search Endurance of the individual SRUs is normally more
critical for aircraft. To calculate on scene endurance for an SRU,
total mission endurance should be determined, contacting the parent
agency if necessary. Time needed for transit to and from the assigned
search area is deducted from total endurance, to obtain on scene
endurance. Search endurance can be assumed to be 85 percent of on scene
endurance, allowing 15 percent for identifying targets.
1. Generally, diversion to identify a target will have no
appreciable effect on area coverage as long as the SRU "fixes"
the location and time of departure from the search pattern and
returns to the same point to resume search within a reasonable
time.
2. When SRUs operate far from home base, they can sometimes be
deployed to an advance base so more time will be available for
searching, and less time will be spent en route to and from
the search area.
C. Sunset is the usual cut-off point for visual searches. Every
time the SRU diverts, available
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