Relatives of Chinese passengers onboard Malaysia Airlines Flight 370 pray during a candlelight vigil for their loved ones at a hotel in Beijing, China, Tuesday, April 8, 2014.Andy Wong/The Associated Press
If the "pings" detected by an Australian naval vessel towing a deep-sea listening device are confirmed as coming from emergency locator beacons on board Malaysia Airlines Flight 370, it could still be months before the treasure trove of data saved inside flight recorders is recovered and divulges its secrets.
The possible stunning breakthrough – a month after the Boeing 777 went mysteriously missing, and after weeks of intensive searching failed to find any floating debris from the jetliner that crashed at sea – came when the metre-long, bat-like detector towed behind the hulking Australian ship, Ocean Shield, "heard" distinctive pings.
Carefully worded cautions failed to dispel hopes that Flight 370, which carried 239 passengers and crew, had finally been found. The doomed jet vanished from air-traffic controllers' radar screens on March 8, abruptly veered away from its intended Beijing-bound course, went silent after someone in the cockpit turned off the plane's usual array of communications devices, and then disappeared. But the plane then flew on for more than six hours. It headed nearly due south after a dog-leg turn that skirted Indonesian radar, until it crashed in a remote region of the southern Indian Ocean after apparently running out of fuel.
Up to a dozen maritime patrol aircraft and ships from several countries have been searching but have not located floating debris in the area roughly calculated from the aircraft's last "handshake" with a communications satellite. The sophisticated long-shot underwater search, though, may have achieved success. The pinger detector must be towed at roughly walking speed and can pick up the pings only within a few kilometres. Yet, within 72 hours of being deployed, it seems to have "found" Flight 370.
"We've got a visual indication on a screen and we've also got an audible signal – and the audible signal sounds to me just like an emergency locator beacon," Angus Houston, head of the Australian joint agency co-ordinating the search and a former air force chief.
Mr. Houston called the Ocean Shield's detection of the once-a-second pings – the first time for about two hours and the second for 13 minutes – "the most promising lead … in the search so far."
The next step on board Ocean Shield will be to launch Bluefin, a small but sophisticated unmanned submarine that looks like a yellow torpedo. It can scan the ocean's bottom, in the inky darkness thousands of metres beneath the surface, with high-resolution sonar capable of building a picture of wreckage or debris.
Bluefin, provided by the U.S. Navy like the pinger detector, was expected to be sent to the bottom as soon as possible in an effort to confirm that the "pings" came from the Boeing 777's wreckage. Visual confirmation that any wreckage is from the white-and-red jet will require a deep-diving, remotely operated submersible equipped with lights. Bluefin can be equipped with a camera and lights once it maps the ocean floor with its sonar.
The ocean is extremely deep at the location – more than four kilometres – and Bluefin will be operating close to limits. The sea bottom in the area ranges from flat – covered with deep, thick ooze laid down over eons – to craggy, rocky, undersea canyons where wreckage recovery would be far more difficult.
With the "pingers" – one each on the flight data and cockpit voice recorders – about to fade into oblivion as their 30-day batteries ebb away, the urgency to confirm the location of the so-called black boxes is mounting.
"Without wreckage, we can't say it's definitely here," Mr. Houston said. "We've got to go down and have a look."
As long as the emergency locator beacons continue to emit their distinctive "pings," acoustic sensors can home in, essentially riding the beacons back to their source.
The Malaysian government – under harsh attack for its mishandling of the early days after the flight went missing and its treatment of distraught families of the victims – voiced hope that the wreck had been found.
"We are cautiously hopeful that there will be a positive development in the next few days," Defence Minister Hishammudin Hussein said Monday.