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

SRUs is generally not a significant problem as long as LORAN,
inertial, SATNAV, OMEGA, or radar navigation aids are
available. DR navigation can cause significant errors in
search pattern execution, even in coastal areas with visual
references. Sea states of three feet or more can also
adversely affect the ability of small surface SRUs to execute
search patterns accurately.
2. Aircraft. High-speed aircraft are more likely to accumulate
turn errors, especially with narrow track spacing, because of
their larger turn diameters. Low-speed aircraft are more
sensitive to wind because the crosswind component will be a
higher percentage of search speed. The following should be
considered when planning aircraft searches:
a. Aircraft navigation accuracy has improved due to
increased use of, and improvements in, navigation computers,
area navigation (RNAV), OMEGA, INS, and LORAN C. More
sophisticated systems can be coupled to an autopilot, enabling
execution of accurate search patterns.
b. When accurate navigation systems are not available,
the type of pattern that requires minimum turns and maximum
search leg length is usually selected to reduce turning errors
and to ease navigation. For high-speed aircraft, patterns and
search area assignments that allow turns outside the search
area should be considered to allow aircraft to establish
themselves on each leg, improving uniformity of area coverage.
(Canadian SRUs always turn outside assigned search areas.)
C. Once large-scale search efforts are under way, redeployment of
SRUs or changing of assigned search patterns becomes difficult. Careful
consideration should be given to selecting patterns and designating
SRUs. Unique patterns based on search circumstances may be developed.
552 Search Pattern Nomenclature
A. Commence Search Point (CSP) is the location in the search
pattern where the SRU begins searching. Specifying the CSP allows the
SRU to efficiently plan the en route track, and ensures that SRUS are
separated and that the SRU begins search at the desired point and time.
B. Search Leg is the long leg along the track of any pattern.
C. Crossleg is the connection between two search legs.
D. Creep is the general direction in which an SRU moves through a
rectangular or square area, normally the same direction as the
crosslegs.
553 Search Pattern Designation
A. A coded system of letters is used to designate search patterns.