Search area descriptions:
Search patterns and the boundaries of search areas are usually described by:
• Geographical Coordinates.
• Universal Grid Reference.
• Track Line.
When a person is reported missing at sea the Master may decide to search the vessel before turning back.
The problem with this situation is that the time period for the person in the water can only be estimated. You may have to take into account the vessel’s leeway but drift should be similar for both vessel and person. At night use searchlights and have people listening for cries of help (engines be slowed/stopped periodically for this purpose).
If the casualty is not located immediately a search should be initiated without delay.
Notify the Rescue Authorities, put out a Pan Pan message on the VHF and MF radio
and display the Man Overboard flag (to notify other vessels that may be in the area). A search datum should be established taking into account the most probable position of the casualty, time elapsed, drift and subsequent information.
Expanding square system - one vessel-
This system starts at the datum point established earlier. The diagram shows the pattern, distance between the tracks will depend on height of lookout and weather conditions but should be such that each sweep should double up on detection.
Sector searching - one vessel:If the incident position was noted and the conditions indicate that the person may not have drifted far from that particular point, the sector search pattern may be used. Remember with this pattern, all changes in course are 120° to starboard.
If the person has not been detected on completion of the first search adjust the original line by 30° and recommence the search pattern. Distance for each leg will vary for types of vessels but may be 1-2 nautical miles.
Parallel track search:
Parallel Track Patterns are normally used when;
• The search area is large and the terrain is level e.g. Maritime Areas.
• Uniform Coverage is required.The location of the target is not known with any precision.
Search legs are aligned parallel to the major or minor axis of the individual search area. The pattern is best used in rectangular or square areas.
A parallel search for two ships- A parallel search for two ships, the search vessels
proceed from one corner of the search area maintaining parallel tracks. The first is at a distance of one–half the track spacing from the side of the area. Successive tracks are maintained parallel to each other and one track spacing apart.
A parallel search for two or more ships-The OSC on the command ship
coordinates the convoy of ships, spreading them abreast of him by “radar distance off” to maintain sweep widths appropriate to the individuals observing platform. Covering a combined track width, the convoy now steams to a point of course change for the next track leg. The OSC signals each vessel of their moment to change course in order to reform the convoy on the new heading at the same track spacing.