MH 370: Missing Malaysian Airliner

[Peter Lemkin]

MH370 crash: Deep-sea search tools ready for deployment

BY TAN YI LIANG

The side scan sonar imagery collected by the Bluefin Robotics deep-sea search submersible is capable of capturing great detail.

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PETALING JAYA: International search and rescue efforts are still scouring the vast surface of the Indian Ocean for debris, but when the time comes for a deep-sea underwater search, the tools for it are ready for deployment.
It has been 23 days since Malaysia Airlines flight MH370 went missing, and 26 nations have contributed both manpower and technology to find the wreckage of the Boeing 777 aircraft, which was said to have ended its journey in the sea.
However, the need to locate the aircraft's flight data recorder - the so-called black box - is growing, and time is fast running out as its on-board batteries are said to be able to last for 30 days before it stops emitting locator pings.
However, what exactly will be used in the event of a deep-sea, underwater search?
Phoenix Towed Pinger Locator 25
According to the US Navy, which operates the Towed Pinger Locator or TPL-25, it is a 29kg system which "meets the Navy's requirement for locating emergency relocation pingers on downed Navy and commercial aircraft down to a maximum depth of 20,000 feet anywhere in the world", according to its page on the official Navy website.
The US Navy's TPL-25 Towed Pinger Locator.

The website explains that the TPL-25 consists of the tow fish, tow cable, winch, hydraulic power unit, generator, and topside control console.
"Navigation is accomplished by using algorithms incorporating the amount of cable in the water, the depth indication from the pressure sensor and other parameters. The generator provides electrical power for the system or power from the support platform can be used if it is compatible. The tow fish carries a passive listening device for detecting pingers that automatically transmit an acoustic pulse," it adds.
The official page adds that most pingers transmit every second at 37.5kHz, although the TPL can detect any pinger transmitting between 3.5kHz and 50kHz at any repetition rate.
"The Pinger Locator is towed behind a vessel at slow speeds, generally from one to five knots depending on the depth. The received acoustic signal of the pinger is transmitted up the cable and is presented audibly, and can be output to either an oscilloscope, or signal processing computer. The operator monitors the greatest signal strength and records the navigation coordinates," it said.
Bluefin-21 autonomous underwater vehicle
The Bluefin-21 is a 750kg, 4.93m-long "modular autonomous underwater vehicle able to carry multiple sensors and payloads at once" according to the Bluefin Robotics website.
The Bluefin-21 autonomous underwater vehicle is launched from a ship.

"It boasts a high energy capacity that enables extended operations even at the greatest depths. The Bluefin-21 has immense capability but is also flexible enough to operate from various ships of opportunity worldwide," said Bluefin Robotics on its official page.
Bluefin Robotics added that the Bluefin-21 is used for off-shore survey, search and salvage, archaeology and exploration, oceanography, mine countermeasures and unexploded ordnance searches.
'Abyss' type deep-sea submarine
Three deep-sea submarines used to search for wreckage of the crashed Air France Flight 447 have also been sent to aid in the search for MH370.
The three "Abyss" type submarines can dive to depths of 6,000m and stay submerged for up to 24 hours.
Two researchers stand behind the "Abyss" deep-sea submarine in this file picture. - EPA

They are used by two organisations, the Helmholtz Oceanography Institute in Kiel, Germany, which owns one and the Woods Hole Institute in Massachusetts in the United States which owns the other two.
The Abyss submarine has bathymetry, temperature, water velocity, salinity, sound speed, sidescan sonar, sound speed, optical backscatter and flourescence sensors, among others.
According to its official page on the Woods Hole Oceanographic Institute website, "the deep ocean version, known as Semi-Autonomous Mapping System (SAMS), dives to 6,000m and can be operated from most any research vessel or ship that can accommodate a portable lab."