MH370 search area too deep for submarine

Published: 12:28PM Tuesday April 15, 2014 Source: AP

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The search area for the missing Malaysia Airlines plane has proved too deep for a robotic submarine.

It was hauled back to the surface of the Indian Ocean less than half way through its first seabed hunt for wreckage and the all-important black boxes, authorities said today.

Search crews sent the Bluefin 21 deep into the Indian Ocean yesterday to begin scouring the seabed for the missing Malaysia Airlines Boeing 777 after failing for six days to detect any signals believed to be from its black boxes.

But after only six hours of its planned 16-hour mission on the sea bed, the autonomous underwater vehicle exceeded its maximum depth limit of 4,500 metres and its built-in safety feature returned it to the surface, the search coordination centre said in a statement today.

What if anything it might have discovered during the six-hour search was still being analysed, it added.

The Bluefin 21 will resume the search today when weather conditions permit, it said.

Search authorities knew that the primary wreckage from Flight MH370 was likely lying at the limit of the Bluefin's dive capabilities. Deeper diving submersibles have been evaluated, but none is yet available in the search area.

The sub would have been programed to return to the surface once it exceeded the 4,500-metre limit, but a safety margin would also have been included to protect the device from damage if it went a bit deeper, said Stefan Williams, a professor of marine robotics at the University of Sydney.

'Maybe some areas where they are doing the survey are a little bit deeper than they are expecting,' he said. 'They may not have very reliable prior data for the area, so they have a general idea. But there may be some variability on the sea floor that they also can't see from the surface.'

Meanwhile, officials were investigating an oil slick about 5,500 metres from the area where the last underwater sounds were detected, said Angus Houston, the head of a joint agency coordinating the search off Australia's west coast.

Crews have collected an oil sample and are sending it back to Australia for analysis, a process that will take several days. Houston said it does not appear to be from any of the ships in the area, but cautioned against jumping to conclusions about its source.

The Bluefin 21 can create a three-dimensional sonar map of any debris on the ocean floor. But the search in this area is more challenging because the seabed is covered in silt that could potentially cover part of the plane.