March issue of the "Firefighting" magazine continued my series of articles on primary search. We are in the middle of a sub-series on large-area search. As you probably remember, in the previous two issues we have covered the basics of searching the large areas, as well as two different approaches to doing it: simply defaulting to small-areas techniques (and thus sacrificing the coverage in the name of safety) and using full-blown methods of large area search that involve separating from the wall under the protection of a search line. We have also looked at what kind of trajectories, or routes you can use in such searches. In March issue we begin discussing how your team members should search the surroundings while advancing along the chosen route.
As the article is in Russian, I will translate its most important points for my English-speaking readers.
- As you probably remember from the first article, I advocate breaking down the problem of large area search into two levels: what route you will use to cover the territory and how your team members will search the area along the chosen route. We have listed various routes in February issue, among them are "Zigzag", "Pendulum" and the "Ruler". In March issue we will start discussing how to search along the route and we will only do this for "Zigzag" route this month. Next month's issue will cover the rest of the routes.
- When studying search tactics for "Zigzag" route, it is critically important to break down numerous methods that are floating around into two broad categories: parallel and intermittent. Parallel methods are those in which the team searches the area at the same time as it advances along the route. In intermittent methods the team stops at predetermined points of the route, searches the surroundings using one or another pattern, and then continues moving along the route to the next predetermined point.
- Regardless of the method selected, all team members must be attached to each other using some sort of leashes when conducting large area search, because even a brief loss of contact on large areas leads to a very significant separation distance. Many teams cannot recover from such separations. The length of the leash will depend on the method of search chosen.
- Parallel method of searching the surroundings is fairly simple: while advancing along the zigzag route, the team leader deploys the search line and two partners follow the team leader on the sides without stopping.
- Partners should be attached to the team leader using arms-length leash, which should be kept under tension. This ensures that there will be no gaps in the coverage of the area along the search line.
- A great way of making an improvised leash that happens to be of the right length is using a 25' webbing sewn into a loop that you should have in your bunker gear pocket for victim packaging anyway. When such a loop is given a knot in the middle with the team leader attached to the center knot and partners attached to the ends of the loop, the entire team will be spaced nearly perfectly while searching. If there are only two members in the team, simply fold the loop and you have a perfect spacer leash for just two firefighters.
- When the wall is reached, the team leader should find an attachment point, tie off the seach line while keeping it taught (we were discussing this in the previous article) and then shift her/his entire team along the wall the distance equal to three leash lengths. This ensures that then next zigzag pass will be adjacent to the previously searched areas without any gaps. Because the distance is measured in leashes, it can be done in zero visibility by simply allowing one of the partners move in desired direction along the wall until the leash becomes taut, then advancing the team leader and remaining partner until they meet the first partner and then repeating the whole procedure two more times (for a total of three times).
- Intermittent methods are also known in some jurisdictions as "butterfly" search patterns. They are pretty popular in large-area search, but unfortunately their true performance is poorly understood. Here are few things you need to know about them:
- The main idea is that the team stops periodically along the route and partners perform a circular search around the team leader. The hope is that the leash can be longer than in parallel search because we don't have to be at the arms length distance while searching during the stop. This is supposed to widen the search area we cover during each zigzag pass, hopefully reducing the number of turns we make while covering large areas. Sadly, though, this does not translate into reduced search time and I will show you why by the end of this article.
- There exist many variants of "butterfly" patterns and they are often being taught as equivalent, and yet, they are not. Some of them are plain unusable in zero-visibility. Overall, there can be six different ways how two partners can search around the team leader, but only those two in which partners terminate their search by bumping into a taut search line work reliably when you can't see anything. Using all other patterns will result in partners not knowing when to terminate their search or becoming entangled in each others' leashes.
- The distance between the stops should be less than the length of the leash, otherwise the circular pattern will result in gaps. An overlap in circular patterns is inevitable if you want to ensure that there are no gaps. Mathematically it can be demonstrated (and has been demonstrated in my book) that the optimal distance between the stops that ensures no gaps and minimizes the overlap is the leash length divided by square root of 2.
- Similarly, the optimal distance the team needs to move along the wall when changing direction in butterfly methods is the length of the leash multiplied by square root of 2.
- An extensive computer modeling of more than half a million different large area search scenarios has revealed that "butterfly" pattern is never faster than parallel search, even when the leashes are several times longer. In fact, intermittent methods are on average 3-4 times slower, and in certain searches they can be up to 11 times slower than parallel method. This happens because in "butterfly" search the team is forced to make stops and cover significant portion of territory several times in order to avoid gaps, so even longer leashes do not help make it faster than parallel search. By the way, these results were also confirmed in numerous practical experiments too. So, if you want to search large areas efficiently using "zigzag" route, do not bother with "butterflies" and always employ a simple parallel search.
- The next month's article will cover the rest of the routes.
This concludes a brief overview of the article. It is only an overview and does not include all the details you need to know about how to lay the routes in large area searches. If you are curious, your department can contact me for details.
If you do understand Russian, you can either download and save a copy of the article in PDF format or you can view it right here on this page.