Finding Malaysian Airlines' doomed Boeing 777 – lost somewhere at sea in the remote reaches of the Indian Ocean after someone in the cockpit "deliberately" changed its Beijing-bound course – could take years and cost a fortune.
"We've been searching for many, many days and so far have not found anything connected with MH370," Angus Houston, the retired former chief of Australia's air force who is now heading the multinational search effort, said Tuesday.
And Mr. Houston raised the grim reality that without any surface debris to point – even vaguely – to an impact site, searching the seabed will require some very big and expensive decisions.
"If we don't find wreckage on the surface we are potentially going to have to, in consultation with other stakeholders, review what we do next," he said. Ultimately that issue is whether the government in Kuala Lumpur is willing to pay for a long, expensive commercial search of the seabed. Currently each contributing nation is paying for the mostly-military surface search by aircraft and ships.
Malaysia, the nation of registry for Flight 370, which apparently was lost in international waters, must, under international law, bear the cost of finding, recovering and investigating the cause of the disaster. That could run into tens – or hundreds – of millions of dollars, with no guarantees of success. As Australia's Prime Minister Tony Abbott put it, the vast search area is "as close to nowhere as it's possible to be."
Time is rapidly running out on what remains the best chance to locate the wreckage of the Boeing 777. Each of its two so-called "black boxes" – actually bright orange flight data and cockpit voice recorders – has locator beacons attached, which emit a special-frequency ping that can be heard by hydrophones. But their range is only a few kilometres and – more importantly – the battery-powered beacons only last for roughly 30 days. The jet crashed on March 8 and the beacons will die soon.
The batteries often last a few days, perhaps as much as two weeks, longer than design life but weaken over time.
"Every day past 30 days is lower and lower probability" of detection, said U.S. Navy Captain Mark Matthews. The navy has sent its Towed Pinger Locator as well as an autonomous submersible to start mapping the seabed. Its detection range is about two kilometres and it must be towed at very slow speed – about three kilometres an hour – to work properly. And as yet searchers have no useful starting point to determine where to tow it over the sea bottom.
A British nuclear-powered submarine, HMS Tireless, which is also capable of listening for the undersea beacons, will join the search but it too will need to be within a few kilometres of the wreckage to capture the pinger beacons.
Even finding floating debris – and none connected to the flight has been found – after four weeks of drifting in powerful currents and varying winds would only narrow the search to an up-current area perhaps hundreds of kilometres long.
Officials are already warning that the big red-and-white Boeing 777 and the secret of why it flew, silent and off-course, for nearly seven hours and thousands of kilometres may take years to find and unravel.
"This search and recovery operation is probably the most challenging I have ever seen," Mr. Houston said.
Should the current intense phase, with military aircraft from more than a half-dozen nations and warships from Australia and China, end without finding floating wreckage, a much-longer, undersea search likely with commercial vessels chartered by Malaysia may follow.
Unless point of impact is roughly determined – that is, where the Boeing 777 eventually slammed into the sea, somewhere in the southern Indian Ocean – search of the bottom, using side-scan sonar that can find wrecks on the bottom, may be unrealistic.
"Right now the search area is basically the size of the Indian Ocean, which would take an untenable amount of time to search," Capt. Matthews said.
"Compare this to Air France Flight 447 [when] we had much better positional information of where that aircraft went into the water," he added, referring to the Airbus A330 that crashed near the equator on a flight from Rio de Janeiro to Paris in 2009.
Even though floating wreckage – including bodies and the big tail fin from the aircraft – was found within 60 hours of the crash, the locator beacons faded out without being detected. France spent at least $50-million (U.S.) and two years of painstaking undersea combing of the bottom with remote-controlled submersibles to find and recover the black boxes.
The amount of floating wreckage also depends on whether the aircraft broke up at altitude – as happened to Air India Flight 182 when a terrorist bomb blew it up off Cork, Ireland, on a flight from Montreal to London in 1985 – or crashes relatively intact as was the case with Air France Flight 447.
That terrorist attack, aviation's worst until the Sept 11, 2001, hijackers turned four U.S. airliners into fuel-filled human-guided missiles, was launched by Sikh separatists operating in Canada.
After the bomb exploded off Ireland, the Air India Boeing 747 left a massive debris field as passengers and luggage were hurled from the broken fuselage. But even with a pinpoint location for impact, it took weeks to locate and recover the flight data recorders.
Soon the black boxes will go silent
Finding the flight recorders, the so-called "black boxes," may determine whether whatever doomed Flight 370 is ever discovered. The two recorders – actually bright orange, armoured and fire-resistant – are designed to withstand impact. Each is equipped with an emergency locator beacon designed to emit a "ping" detectable by undersea hydrophones usually towed close to the bottom.
One recorder stores hundreds of flight parameters, including speed, altitude, control settings, cabin pressure and malfunctions, and keeps track of them second-by-second, usually for at least 24 hours until impact. The other, the cockpit voice recorder, is limited – because pilots don't want their workplace conversations to be recorded for longer – to the last 30 minutes. Given that Flight 370 flew on for about seven hours after someone in the cockpit deliberately changed its course and turned off the usual communications devices, what the pilots said in those critical minutes may never be known even if both recorders are recovered.
Navy undersea ping detector
Looking like a giant yellow bat, the U.S. Navy's undersea "pinger locator" is a sophisticated listening device tuned especially to hear the pings emitted from flight recorders on commercial and military aircraft. The metre-long, 25-kilogram device is towed slowly – very slowly – at about walking speed by a ship on the surface of the ocean. It's designed to operate close to the seabed, in waters as deep as 7,000 metres. The faint acoustic pulses emitted on a special frequency by the pingers on the flight recorders can only be heard a few thousands metres. So unless the detector is deployed very close to the impact point, it may fail to find the recorders before the battery-powered beacons die, usually about 30 days after impact. If a ping is detected, the ship tows the detector across the area to triangulate the location so a remotely-operated submersible with claws can be sent to the seabed to recover the recorders.