UPDATE: Teams searching for the missing Malaysia Airlines plane have reacquired signals that could be consistent with black box flight recorders.
The Australian vessel The Australian Defence Vessel Ocean Shield, towing a US pinger locator, heard the signals again on Tuesday afternoon and evening, search chief Retired air chief marshal Angus Houston said at a mid-afternoon press confrence.
Signals heard earlier have also been further analysed by experts who concluded they were from "specific electronic equipment", he said.
The signal detected on Tuesday afternoon was held for about five minutes and 32 seconds. It was followed by a second signal on Tuesday night, which was held for seven minutes.
"The analysis determined that a very stable, distinct and clear signal was detected at 33.331 kilohertz, and that it consistently pulsed at a 1.106-second interval," Mr Houston said.
''They therefore asses that the transmission was not of natural origin, and was likely sourced from specific electronic equipment. They believe the signals to be consistent with the specification and description of a flight data recorder.''
Reacquiring the the signals has given new hope to the search. The batteries for Fight MH370's flight recorder and voice recorder were due to expire around three days ago.
Flight MH370: Undersea search faces critical decision
EARLIER: Three days have passed since the last flight recorder signals suspected to be from the missing Malaysia Airlines Boeing 777-200.
The Australian Navy ship Ocean Shield is continuing to search off the Western Australia coast for signals.
Search organisers now face a decision over moving to a new phase with the deployment of an unmanned submersible to crawl the ocean floor.
The batteries on the flight’s locator beacons have passed their one-month life, making towed pinger locator useless.
The Ocean Shield cannot use its Bluefin-21 submersible drone and its black box detecting equipment at the same time, search leader Chief Air Marshal Angus Houston says.
Switch decision looms
Any decision to deploy the Bluefin-21 will mark a definitive switch in the search and effectively signal an end to hopes of picking up further location pings.
Other ships and submersibles have been ordered to stay away from the Ocean Shield’s search area as even the slightest noise can confuse the black box detector.
If the search site can be narrowed through the triangulation of the collected underwater pings, then the Bluefin-21 may be all that is needed to discover the wreckage of Flight MH370.
The submerisble can be programmed to conduct a specific search mission of around 20 hours, using side-scan sonar to scroll back and forth looking for unique features on the ocean floor. Once hauled back on board, its data is downloaded and analysed.
If operators on board the Ocean Shield discover an anomaly on the seabed, then the Bluefin-21 will have its sonar scanning equipment stripped off and replaced with a high-grade underwater camera. The submersible can o
Only one of the two systems can be used at a time. Phoenix International Holdings is under contract to the US Navy to provide the Bluefin-21 and towed pinger locator on Ocean Shield.
Air search continues
Though an aerial search for possible plane debris continued, authorities are increasingly of the view that the underwater search offers the best hope of pinpointing a possible crash site before the beacons stop emitting signals, if they haven’t already done so.
“This is the most positive, definitive lead we’ve had and we are pursuing it,” Australian Defence Minister David Johnston says.
“We are throwing everything at this difficult, complex task in at least the next several days while we believe these two pingers involved are still active.”
Beacons on the two flight recorders aboard the plane have an estimated battery life of about 30 days before they stop emitting signals. It has been more than that since the plane vanished on March 8 on a flight from Kuala Lumpur to Beijing with 239 people on board.