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Missing MH370: Facing 'The Underwater Alps'
Confirmation that the Ocean Shield vessel has picked up pings consistent with a plane's black box flight recorders has sparked hope of a breathrough in the hunt for MH370.
But while Malaysia's transport minister spoke of his hope of progress "in days, if not hours" the retired Australian defence chief in charge of the operation has warned that "we are talking about a long operation here".
Sky News experts, maritime explorer Jock Wishart and radar specialist Professor David Stupples, from City University, have been looking at what comes next for searchers working on "the most difficult search in human history".
Which set of signals detected is more likely to be MH370?
Search teams will be keen to investigate the pings detected by the Ocean Shield, but if they are to be thorough, they can not ignore the signals picked up 300 nautical miles away by Chinese ship, the Haixun 01.
They will be hoping to confirm that the 37.5kHz frequency transmissions do lead them to an aircraft's flight recorders.
Prof Stupples said the most recent discovery appeared to be most credible as it had been detected by the more advanced pinger locator on board the Ocean Shield.
He said: "The Chinese were using handheld devices which they would put over the side of a RIB and they received just two or three pings and with the sensitivity of those pieces of equipment it could be that they were just picking up some noise.
"It could be the signal - I'm not dismissing that. But it's probably noise.
The Australian ship was picking up a much more sustained collection of pings, but it was only a few over a two hour period, which means that if it is the black box they were picking up, it is quite some way away.
The Next Steps
Mr Wishart said it would be "incredible" if search teams have managed to track down the black boxes in a search area of some 90,000 square miles of the Indian Ocean.
Royal Australian Air Force aircraft which can drop sonobuoy listening devices have been sent to the area, where the Royal Navy's HMS Echo will also be key.
He said: "Luckily we've got HMS Echo down there, which is a very sophisticated bit of kit and she will do that. I would guess then, if that proves to be not valid, then they will want to move Echo back up North.
"Echo carries items on board which are much more helpful in terms of helping to locate any wreckage there may be, so that would be my next move."
Prof Stupples said: "What they will need to do is get a few more triangulations on these pingers to get the search down to the haystack itself. They've got to get it down to a much smaller area.
"Then they'll send down something like Bluefin - a device controlled from the ship above that will navigate along the sea bed.
"It has sideways-looking sonar, so it will be looking out for wreckage."
Little has been said about the nuclear-powered submarine HMS Tireless but it is understood to have been operating in the search area.
While it can not dive to the same depth as the Bluefin-21 autonomous underwater vehicle, it has incredibly sophisticated sonar equipment which can help with the search for wreckage.
How Long To Recover The Black Boxes?
Mr Wishart said robotic underwater craft could be used to help recover the black boxes if they are confirmed to be at the current search location - which could be 4,500m below the surface.
He said any search could be hampered by sea conditions, which could be treacherous as winter in the southern hemisphere approaches.
The jagged terrain and pressure deep under the surface will also be a challenge for searchers.
Mr Wishart said: "It's the underwater Pennines - maybe even the underwater Alps in terms of some of the stuff you've got down there."
However the search is conducted, he said: "We're not looking at days."
Will The Black Box Recorders Solve The MH370 Mystery?
The flight data recorder should hold up to 15 hours of information from the flight. That would cover the crucial period after contact was lost with air traffic control 38 minutes into the flight and the plane appeared to change course.
But the plane's voice recorder may hold only as little as two hours of information, which could mean that any conversations at that time are lost.
Prof Stupples said: "Everything the plane was doing will be recorded on those data recorders.
"The voice recorder will only have two hours or maybe three and if nothing was being said, nothing will be on that tape.
Are There Lessons For Future Air Travel?
Both Sky News experts agree that the aviation industry needs to look at automatic tracking devices for planes.
Mr Wishart said: "In a world where you can put automatic trackers on cars, it's nonsense that we don't have automatic trackers on planes - something that is completely free of human interference and linked by satellite.
"If that had been the case here, this mystery could have been solved in hours."