Locator for a submerged black box

Produces a precise estimate for the location of a ULB using data collected during a single, non-maneuvering pass of a typical search pattern


News of planes lost at sea routinely raises questions as to why we do not have better devices and techniques to locate these large objects. This was certainly the case with Malaysia Airlines 370 which disappeared in 2014 with 239 souls on board. Planes are mandated to carry underwater location beacons (ULBs), but given the number of aircraft not recovered, better tools are needed.

Previous attempts to improve devices and detection have required changes in airframes, significant retrofits, or incorporated unreliable mechanisms. An ideal solution would be a system that increases the distance at which a ULB can be detected; yields a precise estimate of the beacon location; and does not require costly modifications to the aircraft, data recorders, or acoustic beacons attached to the recorders.

The Navy is ideally motivated and suited to develop such a system and has done so with a detection device with greatly enhanced sensitivity. Towed behind a ship, the underwater apparatus is equipped with a linear sensor array comprising (in one configuration) 32 hydrophones. The device uses a linear acoustic sensor array arranged with an improved directivity index DI enhanced by the spatial response of the array beam pattern.

A useful comparison between existing detection practices and the novel Navy system is the total area of the seafloor from which a ULB signal is likely to be detected. Assuming that the tow body is operated five hundred meters above a level seafloor; the area beneath the tow body for which a ULB signal is likely to be detected in present practices is thirty-eight square kilometers. A search system equipped with the linear sensor array would be equally likely to detect a ULB over a seafloor area totaling seventy-two square kilometers—nearly twice the area covered by present beacon location systems.

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