One of the world's expert wreck hunters believes searchers for the missing Malaysia Airlines plane have pinpointed the crash site and that the recovery of the black boxes is inevitable.
David Mearns, director of Blue Water Recoveries told the ABC's 7.30 program on Tuesday that he was confident that, because of their strength, the four “pings” detected were emitted from the black boxes.
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"I think essentially they have found the wreckage site," he said.
“While the government hasn't announced that yet, if somebody asked me 'technically do they have enough information to say that?', my answer is unequivocally, yes.
“They have got four very, very good detections with the right spectrum of noise coming from them and it can't be from anything else.”
Mr Mearns, an American, was awarded a Medal of the Order of Australia for his work after he found the wreckage of HMAS Sydney in 2008, 66 years after it had been lost in the Indian Ocean during World War II.
He also helped find the wreckage of Air France flight 447 deep in the Atlantic Ocean in 2011.
Mr Mearns believes search officials are being cautious for the sake of the families of the passengers and crew who were on board, while they wait for the Bluefin-21 autonomous underwater vehicle to bring back photographic proof of the plane wreckage.
Each AUV mission takes 16 hours to complete.
The sonar device takes about two hours to descend 4500 metres before scanning a five- by eight-kilometre search area. It then returns to the Ocean Shield vessel for a battery change.
Analysing data from the device can take up to four hours.
Data from the Bluefin-21's first mission, on Monday, which was aborted after six hours, has been analysed but "no objects of interest were found", the Joint Agency Coordination Centre said on Wednesday.
US Navy Captain Mark Matthews, told Fairfax Media that the Bluefin-21 is tasked with surveying a possible debris field and measures the density of the objects which will determine if something is silt or metallic, which could indicate jet wreckage.
Once man-made objects are identified, search operators can reprogram the Bluefin-21 to gather high resolution images.
“You can then then swap out sonar system with imaging system, a camera system to go take pictures of the debris field so you can positively identify that it is aircraft wreckage or something else,” Captain Matthews said.
He also said searchers had “a number of positive indications” they were in the right area, including the four sonar acoustic signals detected and an oil sheen identified on Monday.
Mr Mearns said the breakthrough in the investigation came with the analysis of the MH370 flight path, which helped refine the search area.
“Somewhere out of someplace, fantastic pieces of intelligence were put together to really narrow that down to a small, small area and that's how these guys have been able to find it so quickly,” he said.
“The Ocean Shield was only out there a couple of days and they got a hit. So that has been tremendous success and miraculous.”
A second underwater search is under way after Bluefin-21 was deployed from the Ocean Shield on Tuesday night.
Up to 11 military aircraft, three civil aircraft and 11 ships will assist in the search on Wednesday.
The centre of the search area lies approximately 2087 kilometres north-west of Perth in the Indian Ocean.
- with Aleisha Orr