2.8 Search Patterns

A. Parallel Line. Parallel line search patterns are used when the area of probability is large and the location of craft or person in distress is not well established. The search legs used are parallel to the major axis of the search area. This search pattern can be carried out by single or multiple rescue units. The parallel line search pattern is best used in rectangular or square areas. The rescue units proceed from one corner of the search area maintaining parallel tracks. Successive tracks are maintained parallel to each other and one track spacing apart. This type of search may be carried out by one aircraft or by several aircrafts following parallel tracks or each searching smaller rectangular areas separately.

B. Creeping Line. A creeping line search pattern would be used when there is a stronger probability that the craft or person in distress is closer to one end of the search area. A creeping line search is to be utilized in inshore conditions when the last known position of the victims is known. This search pattern should also be utilized when undertaking search and rescue operations in river and creek mouths. When undertaking a creeping line search the following steps should be utilized:

1. The search pattern shall begin at the last known position.
2. Rescue units shall take a visual reference as a surface marker. This will then provide a continuous reference point during the search.
3. The search lines taken should be close enough so that there is a continuous overlap of vision throughout the search.
4. Rescue units shall work from the last known position and move along search lines that are equally spaced.

C. Expanding Square. This procedure is referred to as an expanding square search as it begins at the reported position or most probable location and expands outwards in concentric squares. It is a very precise pattern and requires accurate navigation. The square search pattern is used when the target is known to be in a relatively small area and the current direction is unknown. This search pattern provides uniform coverage and should be utilized only when operating in the open area.

Search and rescue units should follow the following steps when utilizing this search pattern:

1. The search pattern shall begin at the last known position.
2. Rescue units shall take a visual reference as a surface marker. This will then provide a continuous reference point during the search.
3. The search pattern should begin so that there is a continuous overlap of vision throughout the search.
4. The first two legs are held to a distance equal to the track spacing and every succeeding two legs are increased by a further track space. Turns may be to the left or right at a 90-degree angle, depending upon the observer positions.

Expanding square search patterns utilizing more than one rescue unit should follow the same steps as one rescue unit operations but include the following considerations:

1. The second rescue unit is to commence the same pattern but orientated 45°.
2. If the same speed is used for both rescue units, the first rescue unit must be allowed to complete at least 3 search legs before the second commences to avoid risk of collision.