Flight MH370: search teams racing against the clock to find black box

Search teams are racing against the clock to find the missing Malaysia Airlines flight MH370 as the window for finding one of the black boxes with an active power source gets progressively smaller.

Australia’s defence minister, David Johnston, said on Tuesday that a spell of “reasonable” weather in the Indian Ocean search area meant the sea and air search teams would be stepping up their efforts in the next few days.

On Monday the Australian vessel Ocean Shield detected two separate pulses in the Indian ocean search area consistent with signals emitted by a black box. The first lasted two hours and 20 minutes and the second 13 minutes.

Johnston said 20 sonar buoys had been deployed in the search zone and 14 ships and 14 aircraft were also scouring the ocean where the doomed flight is believed to have disappeared 32 days ago, claiming the lives of all 239 passengers on board. Black boxes emit pulses for about 30 days.

“I want to confirm that we have at least several days of intense action ahead of us. The weather out there today is reasonable,” he said.

The head of Australia’s joint co-ordination centre, Angus Houston, said Ocean Shield was continuing to look for signals from the black box by towing a pinger. An underwater vessel would not be used unless the search area could be narrowed further.

“We will not deploy it unless we get another transmission, in which case we will probably get a better idea about what’s out there,” Houston said.

“If we can get more transmissions we can get a better fix on the ocean floor, which would enable a much more narrowly focused visual search.

“That’s why it’s so important to get another transmission and we need to continue until there is absolutely no chance that the devices are transmitting.”

China's state news agency Xinhua also announced this weekend that a Chinese patrol ship, the Haixun 01, detected a signal that could be from one of the black boxes of the missing plane, about 300 nautical miles from the location of Ocean Shield.

Houston said it was unlikely the Chinese and Australian crews had detected the same source, though he added: "In deep water funny things happen with acoustic signals."

Professor Charitha Pattiaratchi, an oceanographer from the University of Western Australia, said it was not unusual to detect the same signals at such lengths.

“The nature of sounds in the ocean is that they get refracted a lot and can go very long distances,” he said. “For example, we’ve detected off Rottnest Island sounds that are emanated from Antarctica. And in the 1960s they had an explosion in Bermuda that could be detected near Rottnest.

“The Chinese ship may be picking up a signal that is trapped in the surface layer. In deep water the Ocean Shield can go beyond the surface layer where the sound can be trapped, so they can get a more direct signal,” he added.