An Australian ship reacquired signals during a search for the missing Malaysian plane while an analysis of previous pings confirmed the sounds were consistent with those emitted by black boxes.
The Ocean Shield, pulling a U.S. Navy towed pinger locator, detected a signal for five minutes and 32 seconds yesterday afternoon and later in the night heard a ping for about 7 minutes, said retired Air Chief Marshal Angus Houston, who heads Australia’s Joint Agency Coordination Centre. The vessel, which earlier picked up two sounds, is now searching a smaller area. No debris has been found, Houston said.
“We are searching in the right area, but we need to visually identify aircraft wreckage before we can confirm with certainty this is the final resting place of MH370,” Houston told reporters in Perth. “Hopefully with lots of transmissions, we will have a tight, small area and hopefully in a matter of days we will be able to find something on the bottom.”
Investigators are racing against time to pick up pings from Malaysian Airline System Bhd. (MAS) Flight 370’s black boxes because beacons on the cockpit-voice and flight-data recorders are nearing the end of their batteries’ 30-day lifespan. The Boeing Co. (BA) disappeared March 8 en route to Beijing from Kuala Lumpur with 239 people on board, triggering a search that is now the longest for a modern jetliner.
Analysis of pings heard by the Ocean Shield during the weekend determined that a “very stable” signal was detected at 33.331 kilohertz and it consistently pulsed at 1.106 second intervals.
“The assessment is that the transmission wasn’t a natural origin and was likely forced from a specific electronic equipment,” Houston said. “They believe it’s consistent with the specification and description of a flight-data recorder.”
Air and sea patrols continued today over a small area in the southern Indian Ocean off Perth, Australia. Today’s hunt involves 15 aircraft and 14 ships, the JACC said in a statement before the press conference.
Two signals — one lasting two hours and 20 minutes and the other for 13 minutes — were detected over the weekend by the Ocean Shield, which deployed the pinger locator to listen for transmissions.
The Ocean Shield will be at the northern end of today’s search area, which spans 75,423 square kilometers (29,120 square miles) and is centered about 2,261 kilometers northwest of Perth, Australia, the JACC said. That was little changed from a zone of 77,580 square kilometers yesterday.
The search process with the towed pinger locator requires about eight hours for the vessel to make one pass over a search zone.
A ship towing the locator follows a “ladder pattern,” with each leg of the search followed by a second pass in the opposite direction “on a slightly different heading,” the U.S. Navy’s Seventh Fleet said in an e-mailed statement. The course adjustments on each pass steadily expand the patrol zone.
Sending too many ships to the locations where the pings were detected would make the area very noisy, Houston said.
The Ocean Shield has a submersible, the Bluefin-21, ready to launch once the search zone is refined, Houston said. Water depths in the area exceed about 4,500 meters (14,800 feet), and extend down to more than 5,000 meters in parts.
Detecting a pinger signal for more than two hours suggests that what the Ocean Shield picked up was more than a false alarm, according to said John Fish, a principal of Bourne, Massachusetts-based American Underwater Search & Survey Ltd., which has been involved in several efforts to find aircraft that crashed in oceans.
False signals tend to be shorter in duration and difficult to replicate, he said. The ship detecting it a second time also indicates that it may be nearing the crash site, he said.
The side-scan sonar carried by the Bluefin-21 is the same technology that was used to find the remains of Air France Flight 447, which crashed in the Atlantic Ocean in 2009 in 3,900 meters of water. The Bluefin’s operational depth is 4,500 meters.
Locator beacons on the black boxes have non-rechargeable lithium batteries. The power cells like those on Flight 370’s pingers usually last three to five days longer than the 30-day specification at full signal power, according to pinger maker Dukane Seacom, a unit of Hollywood, Florida-based Heico Corp. (HEI/A)
After that, the signal will fade as the batteries weaken and then go dead within days, Dukane Seacom President Anish Patel said last week in an interview.
The range of the pings is a mile, according to manuals from Honeywell International Inc. (HON), the maker of the black boxes. That may make the signals hard to pick up even if an underwater microphone is over the correct location. The pulses from the beacons don’t mark a location, just that the units are nearby.