Unmanned underwater vehicles will only be deployed in the search for the missing Malaysia Airlines plane when another acoustic signal is detected, authorities say.
Two sets of possible black box pings picked up by the Australian vessel Ocean Shield in the southern Indian Ocean – one that was held for two hours and 20 minutes, and another for 13 minutes – remain the best lead so far.
Search co-ordinator Angus Houston said no more signals had been detected since those announced on Monday.
But the former defence force chief said strenuous attempts to pick up more would continue until there was no doubt the black box beacon’s battery, now two days past its 30-day life, had run out.
Batteries often lasted several days longer than that, so there was still hope, he said.
“Unless we find another transmission…”
“Until we stop the pinger search, we will not deploy the submersible … unless we find another transmission,” he told reporters in Perth on Tuesday.
“If we can get more transmissions, we can get a better fix on the ocean floor, which will enable a much more narrowly focused visual search for wreckage.
“If we go down there now and do a visual search, it will take many, many days because it’s very slow, very painstaking work to scour the ocean floor.”
He said some of the false acoustic leads that had been discounted had come from a search ship.
“It got its own transmissions back again. Funny things happen in that environment and you can’t assume things,” he said.
“We think the Ocean Shield transmission is probably the most promising one and we continue to prosecute that.”
Co-operation “absolutely first class”
Defence Minister David Johnston said 14 ships and 14 aircraft continued to look for debris on the ocean surface, and were “flat out trying to enhance that lead and to deliver up something more tangible”.
He declined to comment on reports that the Chinese ship Haixun 01 and British ship HMS Echo, which were operating at the southern end of the search area, were going it alone.
But the co-operation between all of the nations involved had been “absolutely first class”.
Ocean Shield is scouring the northern end of the search area, more than 2000 kilometres northwest of Perth, where the water depth is some 4.5km.
“This is a Herculean task,” Senator Johnston said.
“We have at least several days of intense action ahead of us.
“We are throwing everything at this.”
MH370 with 239 people aboard vanished on a flight from Kuala Lumpur to Beijing on March 8.