LATEST REPORT: Australia's MH370 search chief Angus Houston said Wednesday that he believes the Malaysian jet could be found within days -- raising hopes that the agonising wait could soon be over for relatives of the 239 people on board.
New pings
Australian officials said on Wednesday that two new "ping" signals had been detected in the search for missing Malaysia Airlines Flight MH370, injecting fresh confidence into the search that had been struggling with a lack of information.
Angus Houston, head of the Australian agency coordinating the search, said one ping was detected on Tuesday afternoon and lasted five minutes, 25 seconds, while a second was picked up on Tuesday night and lasted seven minutes.
"I believe we are searching in the right area but we need to visually identify aircraft wreckage before we can confirm with certainty that this is the final resting place of MH370," Houston told reporters in Perth.
The hunt for the 'pings'
Search crews in the Indian Ocean failed to pick up more of the faint underwater sounds that may have been from the missing Malaysian jetliner's black boxes whose batteries are at the end of their life.
The signals first heard late Saturday and early Sunday had sparked hopes of a breakthrough in the search for Flight 370, but Angus Houston, the retired Australian air chief marshal leading the search far off western Australia, said listening equipment on the Ocean Shield ship has picked up no trace of the sounds since then.
Finding the sound again is crucial to narrowing the search area so a submarine can be deployed to chart a potential debris field on the seafloor. If the autonomous sub was used now with the sparse data collected so far, covering all the potential places from which the pings might have come would take many days.
"It's literally crawling at the bottom of the ocean so it's going to take a long, long time," Houston said.
The locator beacons on the black boxes have a battery life of only about a month — and Tuesday marked exactly one month since the plane vanished. Once the beacons blink off, locating the black boxes in such deep water would be an immensely difficult, if not impossible, task.
"There have been no further contacts with any transmission and we need to continue (searching) for several days right up to the point at which there's absolutely no doubt that the batteries will have expired," Houston said.
If, by that point, the US Navy towed pinger locator has failed to pick up more signals, the sub will be deployed. If it maps out a debris field on the ocean floor, the sonar system on board will be replaced with a camera unit to photograph any wreckage.
Earlier, Australia's acting prime minister, Warren Truss, had said the Bluefin 21 autonomous sub would be launched on Tuesday, but a spokesman for Truss said later the conflicting information was a misunderstanding, and Truss acknowledged the sub was not being used immediately.
Houston earlier said the two sounds heard Saturday and Sunday are consistent with the pings from an aircraft's black boxes.
Defense Minister David Johnston called the sounds the most positive lead and said it was being pursued vigorously. Still, officials warned it could take days to determine whether the sounds were connected to the plane that vanished March 8 on a flight from Kuala Lumpur, Malaysia, to Beijing with 239 on board.
"This is a herculean task — it's over a very, very wide area, the water is extremely deep," Johnston said. "We have at least several days of intense action ahead of us."
Houston also warned of past false leads — such as ships detecting their own signals. Because of that, other ships are being kept away, so as not to add unwanted noise.
"We're very hopeful we will find further evidence that will confirm the aircraft is in that location," Houston said. "There's still a little bit of doubt there, but I'm a lot more optimistic than I was one week ago."
Such optimism was overshadowed by anguish at a hotel in Beijing where around 300 relatives of the flight's passengers — most of whom were Chinese — wait for information about the plane's fate.
One family lit candles on a heart-shaped cake to mark what would have been the 21st birthday of passenger Feng Dong, who had been working in construction in Singapore for the past year and was flying home to China via Kuala Lumpur. Feng's mother wept as she blew out the candles.
A family member of another passenger said staying together allowed the relatives to support one another through the ordeal. "If we go back to our homes now it will be extremely painful," said Steve Wang. "We have to face a bigger pain of facing uncertainty, the unknown future. This is the most difficult to cope with."
Investigators have not found any explanation yet for why the plane lost communications and veered far off its Beijing-bound course, so the black boxes containing the flight data and cockpit voice recorders are key to learning what went wrong.
"Everyone's anxious about the life of the batteries on the black box flight recorders," said Truss, who is acting prime minister while Tony Abbott is overseas. "Sometimes they go on for many, many weeks longer than they're mandated to operate for — we hope that'll be the case in this instance. But clearly there is an aura of urgency about the investigation."
The first sound picked up by the equipment on board the Ocean Shield lasted two hours and 20 minutes before it was lost, Houston said. The ship then turned around and picked up a signal again — this time recording two distinct "pinger returns" that lasted 13 minutes. That would be consistent with transmissions from both the flight data recorder and the cockpit voice recorder.
The black boxes normally emit a frequency of 37.5 kilohertz, and the signals picked up by the Ocean Shield were both 33.3 kilohertz, U.S. Navy Capt. Mark Matthews said.
Houston said the frequency heard was considered "quite credible" by the manufacturer, and noted that the frequency from the Air France jet that crashed several years ago was 34 kilohertz. The age of the batteries and the water pressure in the deep ocean can affect the transmission level, he said.
The Ocean Shield is dragging a pinger locator at a depth of 3 kilometers (1.9 miles). It is designed to detect signals at a range of 1.8 kilometers (1.12 miles), meaning it would need to be almost on top of the recorders to detect them if they were on the ocean floor, which is about 4.5 kilometers (2.8 miles) deep.
The surface search for any plane debris also continued Tuesday. Up to 14 planes and as many ships were focusing on a single search area covering 77, 580 square kilometers (29,954 square miles) of ocean, said the Joint Agency Coordination Center, which is overseeing the operation.
Bluefin-21 poised... but 'pings' have stopped
Ships searching for underwater signals from Flight MH370 have heard no more "pings" and will spend several more days trying to pinpoint a crash site before launching a mini-sub to scour the ocean floor, authorities 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 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 Tuesday that while the pings were an exciting development, further transmissions were needed before scouring the ocean floor.
"We need to continue that (search) for several days to the point at which there is absolutely no doubt that the pinger batteries will have expired," Houston said.
"Until we stop the pinger search we will not deploy the submersible."
He said that no further transmissions had been detected in the remote search area off western Australia which could help pinpoint where the jet carrying 239 people might have crashed.
The plane went missing en route from Kuala Lumpur to Beijing on March 8 and the search is now focusing on a 600-kilometre (370-mile) arc of the remote southern Indian Ocean.
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.
But he put a more definitive timeframe on it Tuesday, saying the five-metre (16-feet) long submersible sonar device would not be put into the water unless more transmissions were detected.
"If we go down there now and do the visual search it will take many, many, many days because it's very slow, very painstaking work to scour the ocean floor," he said.
Families of MH370 passengers in Beijing marked the one-month anniversary of the plane's disappearance with a tearful candlelit vigil Tuesday, desperately trying to comfort each other as their agonising wait for news continues.
About two-thirds of the 239 people on board were Chinese.
Sub-marine hunter
The hunt for missing Malaysian Flight MH370 could soon head to the ocean floor using an autonomous sonar vessel after possible black box signals were detected, the head of the Australian-led search operation said Tuesday.
A month to the day since the Boeing 777 disappeared, retired Air Chief Marshal Angus Houston warned that hopes of finding surface debris were fading and that sonic "pings" detected by the Australian naval ship Ocean Shield were the best lead.
Houston told ABC radio Tuesday that once the position of the signals was pinpointed, autonomous underwater vessel Bluefin-21 would be deployed to the ocean floor to search for wreckage.
And this could happen soon.
"I haven't had the discussion this morning, we'll be having that discussion a little later on," he told ABC radio.
"I imagine we'd be getting very close to that point."
The search is now focusing on a 600-kilometre (370-mile) arc of the southern Indian Ocean, far off the West Australian coast.
Houston announced Monday that Ocean Shield had detected underwater signals consistent with aircraft "black boxes", calling it the "most promising lead" so far.
The apparent signals breakthrough came as the clock ticks past the 30-day lifespan of the emergency beacons of the two data recorders from the Malaysia Airlines jet, which vanished on March 8 with 239 people on board en route from Kuala Lumpur to Beijing.
"As a consequence there is a chance the locator beacon is about to cease transmission, or has ceased transmission," Houston said.
"I think it's absolutely imperative to find something else and hopefully when we put the autonomous vehicle down, its capability is such that it'll be able to find wreckage.
"Unfortunately with the passage of time, oceanic drift and all the rest of it -- particularly as a cyclone went through that area in the last few days -- the chances of finding anything on the surface are diminishing with time."
Houston explained that the 4,500m depth of the ocean floor was the absolute operating limit for a Bluefin-21, which is designed for deep sea surveying and can carry video cameras.
"It can't go deeper than that, so it's quite incredible how finely balanced all of this is," he said.
"It's a long, painstaking process, particularly when you start searching the depths of the ocean floor."
Up to eleven military planes, three civilian planes and 14 ships were Tuesday set to take part in the unprecedented search 2,200 kilometres northwest of Perth.
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