After missing Malaysian plane's pingers are dead, then what?

Underwater probes could help find MH370
Underwater probes could help find MH370

    JUST WATCHED

    Underwater probes could help find MH370

MUST WATCH

Underwater probes could help find MH370 02:03

Story highlights

  • Probe of the ocean floor will move from ping locators to sonar
  • The Bluefin-21 is equipped with side-scan sonar
  • And once the debris field is found, investigators would turn to remotely operated vehicles
  • An intact plane could complicate the search effort, CNN analyst says

Once investigators looking for Malaysia Airlines Flight 370 decide to shift from listening for pings emanating from the floor of the Indian Ocean to poring over its terrain, they will begin drawing from a whole new set of tools.

Among them will be the Bluefin-21, a probe equipped with side-scan sonar -- an acoustic technology that creates pictures from the reflections of sound rather than light.

"That is a piece of equipment that does assist in locating where the wreckage may be," said Sylvia Earle, an oceanographer from National Geographic who was chief scientist for the National Oceanic and Atmospheric Administration.

A 'massive, massive task'

Though the discovery of four pings believed to be from the jet's so-called black boxes -- its flight data recorder and its cockpit voice recorder -- have helped investigators narrow the search area, they would still face a formidable task. "It's a lot of terrain to cover," given that the Bluefin-21 moves at the pace of a leisurely stroll, she told CNN.

Though it moves slowly, it creates good images -- so good that they are "almost a picture of what's there ... but it's imaged with sound instead of with a camera."

Listen for a ping, and the water may play tricks on you

PM Abbott confident signals from MH370
PM Abbott confident signals from MH370

    JUST WATCHED

    PM Abbott confident signals from MH370

MUST WATCH

PM Abbott confident signals from MH370 01:01
Searching below the surface
Searching below the surface

    JUST WATCHED

    Searching below the surface

MUST WATCH

Searching below the surface 01:27
Mixed messages on Flight 370
Mixed messages on Flight 370

    JUST WATCHED

    Mixed messages on Flight 370

MUST WATCH

Mixed messages on Flight 370 02:30

Once the debris field is found, then other equipment -- such as remotely operated vehicles -- would be brought in to recover the black boxes, Earle said.

ROVs working at depths of three miles would require power conveyed down a cable from a ship above, she said. "There are not many pieces of equipment in the world able to do this."

And there are only a handful of countries that have manned submarines capable of descending to such depths, she said, citing the United States, Russia, Japan, France and China.

"Having the human presence there can make a big difference," she said. It "can give you a real edge in terms of understanding what's there."

The scarcity of resources "shows how ill-prepared we are to operate in the deep sea," Earle said. "We've invested in aviation and aerospace, and we've been neglecting the ocean."

The time to move from listening for pings to looking for debris is fast approaching, said Alan Diehl, a former Air Force accident investigator. "We're right on the cusp where we need to go from passive listening to active (looking) with the Bluefin," he told CNN.

That's because the batteries powering the black boxes' locator devices are probably already dead, said Mary Schiavo, former inspector general for the U.S. Department of Transportation, who noted that more than four days had elapsed since any pings were detected.

"I'm surprised that they lasted as long as they did," she said.

The failure of searchers to find any debris linked to the plane has not surprised CNN Aviation Analyst David Soucie, author of "Why Planes Crash."

The model used for tracking the debris could be incorrect, he said, noting that that was the case when investigators were searching for evidence of Air France Flight 447, which plunged into the southern Atlantic Ocean in 2009, killing all 228 people aboard.

"They spent weeks looking for debris in the wrong area," he said.

The lack of debris could also mean that the plane did not break apart on impact, but instead sank largely intact, he said.

If that was the case, it could complicate the effort to retrieve the black boxes, since they were stored inside the tail of the plane. Investigators would have to dismantle the tail in order to extract them and whatever secrets they may hold.

Lessons from past air disasters

Where's the debris?

How deep is deep?

      Malaysia Airlines Flight 370

    • nr intv moni basu husbands quiet suffering flight 370_00020822.jpg

      An empty space on earth

      His wife never came home from her flight on MH370, and now K.S. Narendran is left to imagine the worst of possible truths without knowing.
    • This handout photo taken on April 7, 2014 and released on April 9, 2014 by Australian Defence shows Maritime Warfare Officer, Sub Lieutenant Ryan Penrose watching HMAS Success as HMAS Perth approaches for a replenishment at sea while searching for missing Malaysia Airlines flight MH370 in the southern Indian Ocean. Two fresh signals have been picked up Australian ship Ocean Shield in the search for missing Malaysian flight MH370, raising hopes that wreckage will be found within days even as black box batteries start to expire.

      Is this the sound of the crash?

      Was the sound of Malaysian Airlines Flight MH370 striking the water captured by ocean devices used to listen for signs of nuclear blasts?
    •  A crew member of a Royal New Zealand Airforce (RNZAF) P-3K2-Orion aircraft helps to look for objects during the search for missing Malaysia Airlines flight MH370 in flight over the Indian Ocean on April 13, 2014 off the coast of Perth, Australia. S

      Search back to square one

      What was believed to be the best hope of finding the missing plane is now being called a false hope. Rene Marsh explains.
    • Caption:A Chinese relative of passengers on the missing Malaysia Airlines flight MH370 uses a lighter as she prays at the Metro Park Hotel in Beijing on April 8, 2014. The hunt for physical evidence that the Malaysia Airlines jet crashed in the Indian Ocean more than three weeks ago has turned up nothing, despite a massive operation involving seven countries and repeated sightings of suspected debris. AFP PHOTO/WANG ZHAO (Photo credit should read WANG ZHAO/AFP/Getty Images)

      Bring in the lawyers

      Involved parties, including the manufacturer Boeing, are bracing for a long public relations siege.
    • The painstaking search for Malaysia Airlines Flight 370 got a vote of confidence Friday that the effort is headed in the right direction, but officials noted that much work remains.
Credit: 	CNN

      Pings likely not from Flight 370

      Official: The four acoustic pings at the center of the search for Flight 370 are no longer believed to have come from the plane's black boxes.
    • INDIAN OCEAN (April 14, 2014) -- Operators aboard ADF Ocean Shield move U.S. Navy's Bluefin-21 into position for deployment, April 14. Using side scan sonar, the Bluefin will descend to a depth of between 4,000 and 4,500 meters, approximately 35 meters above the ocean floor. It will spend up to 16 hours at this depth collecting data, before potentially moving to other likely search areas. Joint Task Force 658 is currently supporting Operation Southern Indian Ocean, searching for the missing Malaysia Airlines Flight 370. (U.S. Navy video by Mass Communication Specialist 1st Class Peter D. Blair/RELEASED)

      Underwater search on hold

      The underwater search for the missing Malaysia Airlines plane will effectively be put on hold this week, and may not resume until August at the earliest.
    • Movie-makers say they have recruited leading Hollywood technicians to bring their experience to mid-air flight sequences.

      An MH370 movie already?

      Movie-makers in Cannes have announced they're making a thriller based on the disappearance of Malaysian flight MH370.
    • The story of the search

      The search for the missing Boeing 777 has gone on for eight weeks now. CNN's David Molko looks back at this difficult, emotional assignment.