SINGAPORE (NNS) -- USNS Mary Sears moored in Singapore on Jan. 29 after successfully locating a missing airliner which disappeared off the coast of West Sulawesi, Indonesia, on Jan. 1.
Mary Sears joined the search for Adam Air Flight KI 574 in mid-January in response to a request from the Indonesian government, bringing with it search capabilities such as multi-beam, wide angle precision sonar systems that make possible a continued charting of broad strips of ocean floor, helping to locate objects and provide hydrographic data for those areas.
In addition to efforts of the Mary Sears and crew, a six-member U.S. accident investigation team led by the National Transportation Safety Board (NTSB) worked with the Indonesian Search and Rescue (SAR) Command Center to provide technical support to Indonesian authorities.
The search team on board located the pinger signal from the aircraft's black box Jan. 21, during towed pinger locator (TPL) operations. The signal was detected in the search area NTSB recommended, approximately 42 nautical miles off the coast of Sulawesi. The pinger lay at a depth of between 1,500 and 1,900 meters.
"We were very anxious before detecting the pingers," said Lt. Cmdr. Charles Ehnes, Logistics Group Western Pacific's dive officer. "There was concern that if we didn't find the pingers quickly their batteries would run out and then it would be almost impossible to find the wreckage."
This is one of the many considerations a team must make when trying to find a downed aircraft, explained Rick Thiel, salvage project manager with U.S. Navy Supervisor Salvage, part of Naval Sea Systems Command.
"If they were at 50 percent capacity when they went into the water, they would have already expired around the 15th of the month, leaving us unable to use the pinger locator, and only the side scan sonar(SSS)," said Thiel. "It could have made the search take significantly longer, making it much more a game of chance. You could find the debris after your first three passes with SSS, or on your 50th pass. The pinger locator abbreviates the entire process."
Another consideration for a search team are the dangers presented by underwater terrain, according to Thiel.
"One thing we have to pay attention to is the likelihood of the fish [either a side scan sonar or towed pinger locator unit] being dragged into an underwater mountain or cliff," said Thiel. "We have to do a bottom contour survey before we put the fish in the water, otherwise we don't know what we're going to drag them into."
This is another task which can occupy valuable time when racing against the clock. Thiel attributes the crew of Mary Sears with his team's ability to hit the search area running. Since the ship was on station before the survey team, they were in a position to get this kind of work done during the wait.
Once the aircraft's debris field was located, the search team transitioned to mapping the field with high resolution passes of the SSS unit. When the mission was finished, Mary Sears and the search team had mapped three square nautical miles of ocean floor. This is no small task according to Thiel.
"It [mapping] will take several days for an area that big," he said. "For our three nautical mile-long area, this process took about six hours for every pass across the grid including the turn we had to make to line up for our next pass. To cover our selected search area, Mary Sears had to make 18 passes across the area at approximately 3 knots."
Though the search team had the equipment and the knowledge to use it, the search for Adam Air Flight KI 574 was a success through close coordination with Indonesia's government, the National Transportation Safety Board, Naval Sea Systems Command, and other partners. Information from multiple sources was used to locate the aircraft, and, according to Thiel, teamwork was a strong factor in operations at sea.
"My hat's off to the Mary Sears, both the ship's crew as well as the NAVO [Naval Oceanographic Office] detachment on board. They were very professional," said Thiel. "The Indonesian Navy was also very helpful with local ship traffic communication, and with communications between us and SAR headquarters for coordination of ship movement through Indonesian waters."
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