MH-370 signals (1300 sq km wide, 6.5 km deep)

The hunt for the black box recorder goes on, now concentrated on a Los Angeles size area in the Indian Ocean.

It is one level of miracle to pin-point the pings (which are due to be switched off any time now, there is a grace period of about 10 days) and quite another (impossible) challenge to retrieve the recorder from extreme depths (worst case scenario: it is in a trench 5800m deep).
….

An
Australian aircraft picked up a new underwater signal on Thursday while
searching the same part of the Indian Ocean where earlier sounds were
detected that were consistent with an aircraft’s black boxes.


If confirmed, this would be the fifth underwater signal detected in the
hunt for Flight 370, which vanished on March 8 while flying from Kuala
Lumpur, Malaysia, to Beijing, with 239 people aboard.

On
Tuesday, the Australian vessel Ocean Shield picked up two underwater
sounds, and an analysis of two other sounds detected in the same general
area on Saturday showed they were consistent with a plane’s flight
recorders, or “black boxes.”

 

The Australian navy has been
dropping buoys from a P-3 Orion to better pinpoint the location of the
sounds detected by the Ocean Shield.

 
Royal Australian navy
commodore Peter Leavy said each buoy is dangling a hydrophone listening
device about 300 meters (1,000 feet) below the surface. Each buoy
transmits its data via radio back to the plane.

 
The underwater
search zone is currently a 1,300 square kilometre (500 square mile)
patch of the ocean floor, and narrowing the area as small as possible is
crucial before an unmanned submarine can be sent to create a sonar map
of a potential debris field on the seabed.

 
The Bluefin 21 sub
takes six times longer to cover the same area as the pinger locator
being towed by the Ocean Shield, and it would take the vehicle about six
weeks to two months to canvass the underwater search zone, which is
about the size of Los Angeles. That’s why the acoustic equipment is
still being used to hone in on a more precise location, US navy Capt.
Mark Matthews said.

 
The search for floating debris on the ocean
surface was narrowed on Thursday to its smallest size yet — 57,900
square kilometers (22,300 square miles), or about one-quarter the size
it was a few days ago. Fourteen planes and 13 ships were looking for
floating debris, about 2,300 kilometers (1,400 miles) northwest of
Perth.

 
A “large number of objects” were spotted on Wednesday,
but the few that had been retrieved by search vessels were not believed
to be related to the missing plane, the search coordination centre said.


The
locator beacons on the black boxes holding the flight data and cockpit
voice recorders have a battery life of about a month, and Tuesday marked
one month since Flight 370 disappeared. The plane veered off-course for
an unknown reason, so the data on the black boxes are essential to
finding the plane and solving the mystery. Investigators suspect it went
down in the southern Indian Ocean based on a flight path calculated
from its contacts with a communications satellite and analysis of its
speed and when it would have run out of fuel.

 
An Australian
government briefing document circulated among international agencies
involved in the search on Thursday said it was likely that the acoustic
pingers would continue to transmit at decreasing strength for up to 10
more days, depending on conditions.

 
Once there is no hope left of the Ocean Shield’s equipment picking up any more sounds, the Bluefin sub will be deployed. Complicating matters, however, is the depth of the seafloor in the
search area. The pings detected earlier are emanating from 4,500 meters
below the surface — which is the deepest the Bluefin can dive.


Williams said colleagues at the Woods Hole
Oceanographic Institution in Massachusetts had autonomous and remotely
operated underwater vehicles that will dive to 11 kilometers (36,100
feet), although they might not be equipped for such a search.

 
Underwater vessels rated to 6,500 meters (21,300 feet) could search the
sea bed of more than 90 percent of the world’s oceans, Williams said.
“There’s not that much of it deeper than six and a half kilometers,” he said.
 
Williams said it was unlikely that the wreck had fallen into the narrow
Diamantina trench, which is about 5,800 meters (19,000 feet) deep,
since sounds emanating from that depth would probably not have been
detected by the pinger locator.


regards

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