Search for El Faro's 'black box' underway

Members of the El Faro search team prepare the tow pinger locater aboard the USNS Apache in the Bahamas on October 23, 2015.

Story highlights

  • Search for El Faro's voyage data recorder began Friday night
  • Florida-based cargo ship vanished October 1 with 33 people aboard

(CNN)The National Transportation Safety Board tweeted Saturday that the U.S. Navy search team tasked with finding missing cargo ship El Faro began its search with a 'towed pinger locator' -- an instrument designed to detect a downed vessel's "black box."

Naval Sea Systems Command spokesman Chris Johnson told CNN the team arrived at El Faro's last known location northeast of Crooked Island in the Bahamas on Friday night and began searching the 100-square-mile zone immediately. The waters there are about 15,000 feet deep, according to the Navy.
"The Navy's mission will be to first locate the ship and, if possible, to retrieve the voyage data recorder -- commonly known as a black box," officials said in a statement.
    The Jacksonville, Florida-based El Faro disappeared October 1 while making its weekly cargo run to San Juan, Puerto Rico. The ship's 28 American crew members and five Polish nationals are presumed dead.

    Clock ticking on black box

    A properly working black box will emit a signal for 30 days, which means only a week remained upon the team's arrival before the batteries in El Faro's were scheduled to die.
    Locating the container ship's VDR would likely provide insight into the crew's decision-making leading up to and during its ostensibly fatal encounter with Hurricane Joaquin.
    Tote Services, the company that owns the 40-year-old El Faro, confirmed that several pieces of large debris that had washed ashore in the Bahamas came from the doomed ship.

    Same equipment used in MH370 search

    Johnson said the search team will use the pinger locator until it either finds the VDR or its batteries run out.
    The Navy's tow pinger locater that is searching for El Faro's 'black box'
    According to the Naval Sea Systems Command website, "the pinger locator is towed behind a vessel at slow speeds (...) the received acoustic signal of the pinger is transmitted up the cable and is presented audibly ... the operator monitors the greatest signal strength and records the navigation coordinates. This procedure is repeated on multiple track lines until the final position is triangulated."
    It's not the first high-profile mission for this particular towed pinger locator.
    In 2014, it scoured a large swath of the Indian Ocean looking for the still-unrecovered black box belonging to Malaysia Airlines Flight MH370.
    But whereas that search area was massive -- equivalent to the size of New Mexico -- the search area for El Faro is only a fraction of that size -- about half the size of Lake Tahoe.
    It's one of the reasons why Johnson is feeling confident about their chances this time around.
    "If we get out there and can't find the (VDR), we have other options, and those options might be better anyway," he said.
      One of those options is a sonar vehicle called Orion that is towed underwater as it sends back real-time data. Johnson said the team will move on to the Orion if "they determine they are likely not going to locate the signal."
      The other is the remotely operated vehicle called CURV 21 that Johnson said is loaded with "a suite of video equipment."