No more 'pings' heard by ships searching for MH370

PERTH: Ships listening for underwater signals from MH370 have logged no more "pings" and will spend several more days trying to pinpoint a crash site before a mini-sub is launched to scour the seabed, searchers say.
A month to the day since the Boeing 777 vanished with 239 people on board, time is running out to detect further signals as the batteries in beacons on the jet's black box data recorders reach their expiry date.
Transmissions picked up by Australia's Ocean Shield naval ship – consistent with those from aircraft black boxes – had raised hopes that a robotic submersible would soon be sent down to look for debris.
But search chief Angus Houston clarified today that while the pings were an exciting development, further transmissions were needed before deploying the mini-sub.
"We need to continue that (search) for several days to the point at which there is absolutely no doubt that the pinger batteries have expired," Houston said.
"Until we stop the pinger search we will not deploy the submersible."
He said no further transmissions had been detected in the remote search area off western Australia which could help pinpoint where the jet might have crashed.
Houston had indicated that the time was nearing for the Ocean Shield, which is criss-crossing the area to try to home in on the signals again, to launch the US-made autonomous underwater vessel Bluefin-21.
Ocean Shield, which picked up two series of pulses lasting two hours and 20 minutes and then 13 minutes, is operating at the northern end of the defined search area.
China's Haixun 01, which has also reported some acoustic sounds, and Britain's HMS Echo are working the southern end.
Houston said the Ocean Shield transmissions were the most promising, adding that the advice from black box manufacturers was that the frequency of the signals could have changed.
"There's a change with the pressure on the ocean floor and the age of the particular batteries ... you get changes in the transmission level," he said.
While 14 ships were involved in the search, it was not possible to crowd the area due to the need for silence, he said.
"We can't have too many ships in the area because when you're dealing with these transmissions you need utter silence," he said. – AFP