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Australian authorities think pings are from black box

Tony Abbott told reporters in Shanghai that crews hunting for Flight
370 have zeroed in on a more targeted area in their search for the
source of the sounds, first heard on Saturday.

"We have very much narrowed down the search area and we are very
confident that the signals that we are detecting are from the black box
on MH370," Abbott said.

"Nevertheless, we're getting into the stage where the signal from what
we are very confident is the black box is starting to fade," he added.
"We are hoping to get as much information as we can before the signal
finally expires."

The plane's black boxes, or flight data and cockpit voice recorders,
may hold the answers to why the Boeing 777 lost communications and
veered so far off course when it vanished March 8 while flying from
Kuala Lumpur, Malaysia, to Beijing with 239 people on board.

Search crews are racing against time because the batteries powering the
devices' locator beacons last only about a month — and more than a
month has passed since the plane disappeared. Finding the black boxes
after the batteries fail will be extremely difficult because the water
in the area is 4,500 metres deep.

The Australian ship Ocean Shield is towing a U.S. Navy device that
detects black box signals, and two sounds it heard Saturday were
determined to be consistent with the signals emitted from aircraft
flight recorders. Two more sounds were detected in the same general area
on Tuesday.

"We are confident that we know the position of the black box flight
recorder to within some kilometres," Abbott said. "But confidence in the
approximate position of the black box is not the same as recovering
wreckage from almost 4

1/2 kilometres beneath the sea or finally
determining all that happened on that flight."

An Australian air force P-3 Orion, which has been dropping sonar buoys
into the water near where the Ocean Shield picked up the sounds,
detected another possible signal on Thursday, but Angus Houston, who is
co-ordinating the search for Flight 370, said in a statement that an
initial assessment had determined it was not related to an aircraft
black box.

The buoys each have a hydrophone listening device that dangles about
300 metres below the surface and their data is sent via radio back to a
plane, Royal Australian Navy Commodore Peter Leavy said.

The Ocean Shield was still towing its pinger locator to try to find
additional signals on Friday, and the Orions were continuing their hunt,
Houston said. The underwater search zone is currently a
1,300-square-kilometre patch of the ocean floor, about the size of the
city of Los Angeles.

"It is vital to glean as much information as possible while the
batteries on the underwater locator beacons may still be active,"
Houston said in a statement.

The searchers are trying to pinpoint the exact location of the source
of the signals so they can send down a robotic submersible to look for
wreckage. Houston said on Friday that a decision to send the sub could
be "some days away."

The Bluefin 21 submersible takes six times longer to cover the same
area as the pinger locator being towed by the Ocean Shield and would
take six weeks to two months to canvass the current underwater search
zone.

Complicating matters is the depth of the seabed in the search area. The
signals are emanating from 4,500 metres below the surface, which is the
deepest the Bluefin can dive. The search co-ordination centre said it
was considering options in case a deeper-diving sub is needed.

Meanwhile, the centre said the surface area to be searched for floating
debris had been narrowed to 46,713 square kilometres of ocean extending
from 2,300 kilometres northwest of Perth. Up to 15 planes and 13 ships
were conducting the visual search Friday, west of the underwater search
based on expected drift from the suspected crash site.

Investigators believe the plane went down in the southern Indian Ocean
based on a flight path calculated from its contacts with a satellite and
analysis of its speed and fuel capacity.

Separately, a Malaysian government official said Thursday that
investigators have concluded the pilot spoke the last words to air
traffic control, "Good night, Malaysian three-seven-zero," and that his
voice had no signs of duress. A re-examination of the last communication
from the cockpit was initiated after authorities last week reversed
their initial statement that the co-pilot was speaking different words.

The senior government official spoke on condition of anonymity because he wasn't authorized to speak to the media.