Malaysia Airlines MH370: Ocean Shield detects two more signals in search for missing flight

Updated

An Australian search vessel has picked up two more signals from what could be the black box from missing Malaysia Airlines flight MH370.

The man in charge of the search, retired Air Chief Marshal Angus Houston, says the Ocean Shield picked up the traces on Tuesday afternoon and late on Tuesday night Perth time.

Ocean Shield has now detected four signals in the same area less than 40 kilometres apart, and Air Chief Marshal Houston believes the search is closing in on MH370's "final resting place".

The planned search area has been reduced over the past few days and now covers 75,000 square kilometres.

Air Chief Marshal Houston says he is confident the search is in the right area.

Sorry, this video has expired Video: Angus Houston says more pings detected (ABC News)

"I think we're looking in the right area, but I'm not prepared to confirm anything until such time as somebody lays eyes on the wreckage," he said.

Air Chief Marshal Houston says the Ocean Shield will be looking to pick up more transmissions which would help to better pinpoint where the signal was coming from.

He says once the search area has been narrowed down, searchers could then find something in a "matter of days".

"Hopefully with lots of transmissions we'll have a tight, small area and hopefully in a matter of days we will be able to find something on the bottom that might confirm that this is the last resting place of MH370," he said.

The reduced search area has also led to a boost in visual search operations on the ocean surface. Up to 11 military aircraft, four civil aircraft and up to 14 ships are involved in the search.

The Australian Air Force is also dropping sonar buoys into the water to help pick up more signals.

Both signals picked up on Tuesday lasted just over five minutes.

What is the Bluefin-21?

An autonomous underwater vehicle (AUV) designed for deep-sea surveying.

It has a "swappable payload". It will first use sonar in the search and will be refitted with cameras if something is detected.

It's 5m long and weighs 750kg. Has an endurance of 25 hours underwater at a speed of 3 knots, with a top speed of 4 knots.

It has a depth rating of 4,500m, meaning it will be at its limit in the Indian Ocean search zone.

Bluefin Robotics says its AUV can also be used for archaeology, oceanography, mine countermeasures, and unexploded ordnance.

The signals are becoming weaker and Air Chief Marshal Houston says that is most likely because the batteries are beginning to run out.

Once the signal dies, an autonomous underwater vehicle called the Bluefin-21 will be deployed to scan the ocean floor, which is more than four kilometres deep.

Air Chief Marshal Houston says an underwater search could present its own challenges.

"I'm informed by experts that there's a lot of silt down there," he said.

"That could complicate the search because the silt on the bottom of the ocean can be very thick and things disappear into it and it makes a visual search underwater very difficult."

He says an underwater search can take up to six times longer to cover the same area as a search on the surface.

Signals cannot be used to officially verify the missing plane, and Air Chief Marshal Houston says he wants more.

"I'd just like to have that hard evidence - a photograph - that there are pieces of evidence down there," he said.

Once located, a new type of submersible will be needed to bring the wreckage to the surface, and hopefully find the crucial flight data and voice recorders.

Meanwhile, preparations are underway in Perth to accommodate the families of those missing on the flight.

Topics: air-and-space, disasters-and-accidents, accidents, perth-6000, wa, australia, malaysia, asia

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