Another long-drawn-out search?

The crash, initial search

It is now seven weeks since MH370 went missing, en route from Kuala Lumpur to Beijing. The Boeing 777-200ER vanished from air traffic control screens about 50 minutes after it departed with 239 passengers and crew on board.

Based on analysis of satellite data by London-based Inmarsat, Malaysian authorities are certain the plane crashed into the southern Indian Ocean. But they are unable to pinpoint the exact site.

The plane's communication systems were shut down - deliberately it is believed - at least six hours before the presumed crash.

On June 1, 2009, Flight AF447, an Airbus A330-203, was flying from Rio de Janeiro to Paris with 228 people on board when it plunged into the Atlantic Ocean with no survivors.

Flying amid stormy weather, the aircraft was due to leave Brazil airspace and enter Senegal at 2.20am. But more than one and a half hours later, the pilots had still not contacted air traffic control. Attempts to reach them also failed. By early afternoon, the plane was declared lost - presumed crashed.

It took six days before the Brazilian navy found the first debris and bodies. Four days later, a French nuclear submarine arrived at the site to assist in the search for the flight recorders, also known as black boxes.

The United States supported the search with underwater devices capable of picking up signals that the black boxes emit.

By mid-July - a month and a half after the crash - the black boxes, which had stopped emitting signals, were still not found. The search was temporarily suspended.

The hunt for MH370 has now crossed the one and a half month mark. For more than a week now, a submersible US-made sonar device called Bluefin-21 autonomous underwater vehicle (AUV) has done daily sweeps of the ocean floor some 4.5km deep and 2,000km north-west of the Australian city of Perth.

Over 80 per cent of the current 10km-radius search area around the site of an acoustic detection - believed to be from the aircraft's black boxes - on April 8 has been covered.

If nothing is found by the time the sweep is completed, search teams will, as they did in the Air France case, regroup and re-assess their options.

Phase 2 of search for AF447

In late July 2009, the hunt resumed in an area not covered earlier.

It was led by a French research vessel using a towed sonar array, which consists of a long cable with an array of hydrophones that trails in the water.

After about three weeks of finding nothing, the search was called off in late August that year. The total bill so far had been borne by France, Air France and the plane's maker, Airbus.

Phase 3

Search teams took a seven-month break before starting to look again in April 2010. This time, the search lasted about two months, with the airline and Airbus footing the bill.

During the months in between, a new search area was drawn up by oceanographers from France, Russia, Britain and the United States. They did this by combining data on the location of floating bodies and wreckage, and currents in the mid-Atlantic in the days right after after the crash.

A smaller area to the south-west was also searched, based on a re-analysis of sonar recordings made by the French submarine the previous year.

There were two simultaneous search efforts undertaken by the US Navy/Phoenix International and the Woods Hole Oceanographic Institute. Both involved the use of more powerful sonar equipment.

Australian authorities searching for MH370 have said in recent days that they are considering deploying more powerful sonar equipment to scan for debris on the seabed.

Malaysia's Acting Transport Minister Hishammuddin Hussein said on Friday that a preliminary report on the missing airline would be released this week but that it would contain "nothing exciting", Bernama reported.

For the AF447, the third phase of the search had also come up with nothing.

The final phase

After the lack of success, French authorities engaged US-based search consultancy Metron in July 2010 to re-analyse all available data, including the results from previous searches.

The Metron team recommended resuming the search in an area close to the aircraft's last known position. On April 3, 2011, the search resumed.

A week later, experts from the Woods Hole Oceanographic Institute found the wreckage - nearly two years after the plane had crashed.

On May 7, the flight recorders were taken aboard a French navy vessel for delivery to Paris.

Between May 5 and June 3, 104 bodies were recovered from the wreckage, bringing the total number of bodies found to 154.

The search cost a total of 115 million euros (S$200 million). And 74 bodies still remain missing.

This article was published on April 27 in The Straits Times.

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