A towed pinger locator is a water-borne device used to locate the sonar "ping" from the underwater locator beacon which is fitted to the

Cockpit Voice Recorder A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents. The device may often be referred to colloquially as a "black box", an outdated nam ...

s and

Flight Data Recorder A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents. The device may often be referred to colloquially as a "black box", an outdated nam ...

s installed in commercial airliners. They can locate pingers at depths of up to underwater.

Description

The locator is mounted in a hydrodynamic shell, or "tow fish", connected by winch behind a surface vessel across the search area. The locator listens for the sound emanating from the beacon or "pinger". Once located, the beacon and its attached recorders can be retrieved by divers,

submersible A submersible is an underwater vehicle which needs to be transported and supported by a larger ship, watercraft or dock, platform. This distinguishes submersibles from submarines, which are self-supporting and capable of prolonged independent ope ...

s or remotely operated vehicle (ROV), depending on depth. A model currently used by the

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

is the TPL-25, which has a weight of and a length of ; it is generally towed at . Most beacons transmit a pulse once a second at 37.5 kHz. The

hydrophone A hydrophone () is a microphone designed for underwater use, for recording or listening to underwater sound. Most hydrophones contains a piezoelectric transducer that generates an electric potential when subjected to a pressure change, such as a ...

must be positioned below the

thermocline A thermocline (also known as the thermal layer or the metalimnion in lakes) is a distinct layer based on temperature within a large body of fluid (e.g. water, as in an ocean or lake; or air, e.g. an atmosphere) with a high gradient of distinct te ...

layer which reflects sounds, either back to the surface or back to the ocean floor. Since the pinger signal is relatively weak, the hydrophone must be within a

nautical mile A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute ( of a degree) of latitude at t ...

(about ) to detect it. The hydrophone is typically deployed about above the ocean floor, where it can scan a swath approximately wide, on a flat, level surface.

References

{{reflist Aircraft emergency systems Beacons

Description

See also

References