April 17, 2014, 2:41 a.m. EDT, wsj
Hunt for missing MH370 took a gamble on location
By Daniel Stacey
A combination of cutting-edge science, dogged analysis and simple luck prompted searchers to focus the hunt for Malaysia Airlines Flight 370 underwater, just days before the plane's black box recorders were expected to fall silent.
Authorities got a first look at the sea floor Tuesday in an area that they believe is the jet's likely location, without detecting any wreckage. Hopes rest on a remote-controlled submersible from the U.S. Navy, which is seeking the first visual confirmation of wreckage that could lead investigators to the all-important recorders.
It's a turn of events that seemed unimaginable less than two weeks ago, after an extensive air and sea hunt for surface debris had turned up little more than garbage. The frequent and seemingly fruitless shifts in the aerial search frustrated investigators and eroded the confidence of the public and families of the victims. The current effort may yet turn out to be another false lead.
But over the past 11 days, an international team of experts has persistently recalibrated data and capitalized on new streams of information to zero in on a tight corridor in the southern Indian Ocean, according to senior Australian government officials, investigators from several countries and others briefed on the probe.
The decision to narrow the search on April 4 amounted to a carefully calculated gamble. Investigators incorporated arcane new calculations reflecting changes in the operating temperatures of an Inmarsat PLC satellite as well as the communications equipment aboard the Boeing 777 when the two systems exchanged so-called digital handshakes. Those links occurred regularly for some six hours after the plane deviated from its original flight path to Beijing from Kuala Lumpur, and then headed south.
The new analysis provided investigators with a "sweet spot" to begin the underwater search, initially using a black-box detector in an area of sea some 500 kilometers to the north of where military aircraft and ships had previously been looking, said Martin Dolan, chief commissioner of the Australian Transport Safety Bureau.
The international working group established by Malaysia to investigate the crash, which included U.S., British, and French technical experts, assembled the new analysis, which the ATSB vetted before incorporating into the Australian-lead search.
"There's a set of assumptions, some of which are factually checkable, others of which remain assumptions," Mr. Dolan told The Wall Street Journal. "We knew we were running out of time."
The revised data also indicated the jet, carrying 239 people, may have been flying toward the Western Australian city of Perth and possibly traveling on autopilot when it crashed on March 8, though those specifics haven't been confirmed, he said.
Nine days after the jet disappeared from civilian radar, search crews spent 10 days scouring an area of ocean for floating wreckage without success. Then the operation was abruptly moved to a new location some 1,100 kilometers northwest of Perth, based on new military radar data.
The narrowing of the search on April 4, which defined where the Australian naval vessel Ocean Shield would tow the U.S. black box locator, took into account factors including the position of the Inmarsat satellite relative to the sun.
Crucial to Inmarsat's analysis of the pings was the Doppler effect: the change in frequency of sound or other waves depending on movement of their source relative to their recipient. Luck emerged when signals believed to come from the plane's recorders were detected past the equipment's intended 30-day useful life.
Investigators relied on the principle that the satellite's temperature distorts the way it receives radio waves. The investigators analyzed changes in the temperature of the Inmarsat satellite on each occasion that the plane made contact and then made calculations about the jet's trajectory, according to Warren Truss, Australia's deputy prime minister.. Investigators also incorporated aircraft performance calculations from Boeing to fix the sweet spot, according to Mr. Dolan, developing the most precise projection yet of the jet's probable point of impact.
At the same time, investigators further refined those projections by evaluating data from hundreds of other flights with similar equipment that crisscrossed the same region, according to Inmarsat officials. That established a baseline to better calculate where Flight 370 was presumed to have gone down.
"The Inmarsat model was designed for fine tuning," said Inmarsat Senior Vice President Chris McLaughlin, who said it revised the search area continually as new information arrived.
The revelations about how the search proceeded help to explain why the Australia's Ocean Shield vessel was able to detect a string of acoustic signals, believed to have come from the plane's black box recorders, within 48 hours of starting its underwater search on April 4. And also why authorities, including Australia's Prime Minister Tony Abbott, were so quick to declare their confidence that they were closing in on the jet's location.
"We still haven't come up with a different alternative theory as to what it might be if it's not the pinger, but we're never going to give you a guarantee on this," Mr. Dolan said.
When no new underwater signals from the recorders were detected in nearly a week, authorities deployed an unmanned submersible to scan the seabed for signs of plane wreckage Monday. The primary goal remains recovering Flight 370's flight-data and cockpit-voice recorders, in the hope they might reveal what befell the jet.
After completing about six hours of its first mission Monday, the submersible reached its operating depth limit of about 3 miles, and its built-in safety feature returned it to the surface, underscoring just how difficult and protracted its mission is. The boundaries of the Bluefin-21's search zone encompass roughly 500 square miles. The device moves at a walking pace, and scanning the entire search area was expected to take between six weeks and two months.
In the end, even Angus Houston, the former Australian military chief coordinating the search, acknowledges that luck has played a part in the effort. "The batteries of both devices are past their use-by date and they will very shortly fail. I think we are very fortunate in fact to get some transmissions on Day 33," he said last Wednesday.
Describing the decision to switch to underwater searches, Mr. Houston told reporters "I think we have probably got to the end of the process of analysis." Noting that "the data we've got is the data we've got," he added "we'll proceed on the basis of that."
