A Chinese ship twice detected a “pulse signal” at a frequency used by aircraft black boxes, while an Australian vessel is investigating a separate “acoustic noise” in the search for flight MH370.

Retired Air Chief Marshal Angus Houston, who is co-ordinating the search, told reporters in Perth on Sunday the Chinese ship Haixun 01 had detected two “acoustic events” which provided “some promise” and required a full investigation.

The first signal was detected on Friday and the second, which lasted 90 seconds, was detected on Saturday within two kilometres of the original detection.

“This is an important and encouraging lead but one which I urge you to continue to treat carefully,” Air Chief Marshal Houston said.

He warned no signals or objects found in the ocean had been verified as being from the missing Malaysia Airlines plane.

British naval ship HMS Echo would arrive in the search zone in about 14 hours, he said.

Australian naval vessel Ocean Shield is looking at another “acoustic noise” in a separate area and will go to the zone when that task is completed.

Air Chief Marshal Houston said he only learned about Ocean Shield’s detection on Sunday morning and it could be a couple of days until the search was resolved.

“We will pursue these leads to their conclusion,” he said.

FOCUS ON SIGNALS | AUSTRALIA HOPEFUL, NOT CERTAIN

Angus Houston speaks to media at this morning's press conference. Picture: Simon Santi / The West Australian

Air Chief Marshal Houston said there had been “fleeting acoustic events” rather than a continuous transmission.

“If you get close to the device, we should be receiving it for a longer period of time than just a fleeting encounter,” he said.

“But we’ve got a transmission (so) we must investigate it.”

Corrected satellite data indicated the ill-fated Malaysia Airlines plane might also have been travelling faster, which meant the search was moving further south - to about where Haixun 01 was - but was still within the same search zone, Air Chief Marshal Houston said.

He added that it was a “painstaking process” and there had been few leads so far that had narrowed down the search area, warning there could be similar unverified leads over the coming months.

Air Chief Marshal Houston said because the Chinese search area was 4.5km deep, any recovery operation would be demanding and take a long time.
But he stressed that authorities would first have to establish that there was actually something there.

“We’re a long way from making that conclusion,” he said.

It is now day 30 of the search and near the end of the black box emergency beacon’s battery life.

While the battery could last an extra eight to 10 days beyond that, Air Chief Marshal Houston admitted they were running out of time.

He also defended Australia’s relationship with China, saying he became aware of the first Chinese signal detection quickly because there was a journalist on board but was also informed by the Chinese government about the same time.

He said he learned about the second ping “quite some time ago“ and was “very satisfied” with the level of communication from the Chinese.

The Boeing 777 was carrying 239 passengers when it vanished on March 8 en route from Kuala Lumpur to Beijing, triggering an international search that started in the South China Sea before shifting to the Indian Ocean.

Up to 10 military planes, two civilian aircraft and 13 ships are assisting in Sunday’s search for the missing plane, about 2000km northwest of Perth, totalling about 216,000 sq km.

The Haixun 01 signal, which lasted for 90 seconds, was picked up during searches on Saturday. The Chinese ship had already detected a more fleeting signal on Friday, Houston said.

He described the development an "important and encouraging lead but one which I urge you to continue to treat carefully".

"We are working in a very big ocean and within a very large search area, and so far since the aircraft went missing we have had very few leads which allow us to narrow the search area," he said.

Air Chief Marshal Houston urged caution, saying he did not want to put the families of those onboard the missing flight under further stress.

He said the ocean in the Chinese search area was 4.5km deep, so any recovery operation would be demanding and take a long time.

A Chinese Ilyushin IL-76s aircraft taxies at Perth international airport en route to rejoin the search operation for wreckage and debris of the missing Malaysia Airlines Flight 370 in Perth, near the coast of western Australia, Sunday, April 6, 2014.. Picture: AP Photo/Rob Griffith

Signal hope

The signal detected on Friday matches the frequency used by beacons attached to the flight data recorder and the cockpit voice recorder on the Malaysia Airlines Boeing 777, the manufacturers Honeywell Aerospace have said.

Four weeks exactly after the jet, carrying 239 people, went missing during an overnight flight from Kuala Lumpur to Beijing, the official Xinhua news agency yesterday reported that a black box detector on board the Chinese search ship picked up a signal at a frequency of 37.5kHz.

The Chinese search ship Haixun 01 picked up the pulse signal at about 25 degrees south latitude and 101 degrees east longitude, Xinhua said in a brief dispatch Saturday.

Air Chief Marshal Houston said the reported characteristics of the signal "are consistent with the aircraft black box".

A number of white objects were also sighted on the surface about 90 kilometres from the detection area, he said, according to a statement by the Joint Agency Coordination Centre (JACC).

However, he warned: "There is no confirmation at this stage that the signals and the objects are related to the missing aircraft."

Australia has asked China for more information, he said, and was considering deploying search assets to the area.

Chinese officials also warned the signal had not yet been identified.

"Suspected pulse signal picked up by Haixun 01 has not been identified yet," the China Maritime Search and Rescue Center said on a verified microblog.

Prime Minister Tony Abbott cautioned against coming to "hard and fast" conclusions.

Mr Abbott reminded people that the search was the most difficult in "human history".

"While we certainly are throwing everything we have at it, and while the best brains and the best technology in the world will be deployed, we need to be very careful about coming to hard and fast conclusions too soon," he told reporters in Tokyo.

Australian Defence Minister David Johnston echoed the words of caution.

"This is not the first time we have had something that has turned out to be very disappointing," he told ABC television.


Race against time

The possible development comes nearly a month into the unprecedented multinational search for MH370, its 227 passengers and 12 crew.

Up to 10 military planes, three civilian jets and 11 ships are currently involved in the protracted search for the Boeing 777, but have so far failed to find any sign of the plane.

Today's search involves up to 10 military planes, two civilian planes and 13 ships.

The Australian Maritime Safety Authority (AMSA) has three separate search areas planned for today about 2000km north west of Perth, which total approximately 216,000 square kilometres.

The Join Coordination Centre said this morning that weather in the search area was expected to be good with a cloud base of 2,500 feet and visibility greater than 10km.

"The Australian Transport Safety Bureau continues to refine the area where the aircraft entered the water based on continuing ground-breaking and multi-disciplinary technical analysis of satellite communication and aircraft performance, passed from the international air crash investigative team comprising analysts from Malaysia, the United States, the UK, China and Australia," the centre said in a statement this morning.

The hunt for the plane concentrated Saturday on about 217,000 square kilometres of the Indian Ocean some 1,700 kilometres (1,054 miles) northwest of Perth.

Australian and British vessels are currently involved in a round-the-clock underwater search hoping to pick up a signal from the black box, but the battery powering those emissions is nearing the end of its roughly 30-day life span.

The Ocean Shield, which is carrying a US Navy black box detector, and HMS Echo, which has a similar capability, are searching a 240-kilometre track of ocean in hopes of detecting sonic pings from the recorder.

Chinese patrol ship Haixun 01 is pictured during a search for the missing Malaysia Airlines flight MH370, in the south Indian Ocean April 5, 2014, in this photo courtesy of China News Service. Picture: REUTERS/CNSphoto

However, progress is painstaking as vessels must move slowly to improve readings, and officials have acknowledged there is no solid evidence the plane went down in that stretch of sea.

Malaysian authorities believe satellite readings indicates MH370 crashed in the Indian Ocean, far off Australia's western coastline, after veering dramatically off course.

But no proof has been found that would indicate a crash site, and Australian Prime Minister Tony Abbott has described the oceanic search as "the most difficult in human history".

JACC said Australia's Transport Safety Bureau was continuing "to refine the area where the aircraft entered the water" using further analysis of satellite data and aircraft performance.

Several nations that normally do not work together -- notably the United States and China -- have rallied to help look for clues.

But authorities still have no idea how or why the plane vanished, and warn that unless the black box is found, the mystery may never be solved.


Caution and optimism

Anish Patel, president of US black box beacon manufacturer Dukane Seacom, said he was "highly sceptical" about the Chinese report Saturday.

"I would like to understand why not two signals -- there should be a second beacon from either the flight data recorder or the voice recorder. So if the recorders are adjacent or within reasonable proximity... they should have detected possibly two signals," he told CNN.

"So let's get some additional assets in the water so we can corroborate, before we get everyone's hopes up, before we disappoint these families one more time I think we need to corroborate."

But Charitha Pattiaratchi, a professor of coastal oceanography at the University of Western Australia, said the news was exciting.

"The 35.7 kHz is a man-made noise. There's not another noise at that frequency," he told AFP, adding that this was exactly why black box pingers were set at this frequency.

"A whale or a dolphin or rain or an underwater earthquake... they have a completely different frequency."

Earlier in Kuala Lumpur, Transport Minister Hishammuddin Hussein said Malaysia would, in line with international agreements, appoint an independent "investigator in charge" to lead an international team to probe what happened to MH370.

The team will include Australia, China, the United States, Britain and France.

Hishammuddin again declined to provide any detail from Malaysia's ongoing investigation, however, saying he remained focused on finding the plane and its black box.

"In spite of (the long odds), our determination remains undiminished," he told a press briefing.

The West Australian

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