JAKARTA: Indonesian divers on Thursday (Nov 1) retrieved a black box from a Lion Air passenger jet that crashed into the sea, killing all 189 people on board.
The black box should provide clues to what went wrong after flight JT610 lost contact with ground staff just 13 minutes after taking off early on Monday from Jakarta, on its way to the tin-mining town of Pangkal Pinang.
The device, identified as the flight data recorder, will be handed over to Indonesia's transportation safety committee, authorities said.
The box was recovered at 10.05am by a diver from the Indonesian Armed Forces in waters off Tanjung Karawang, West Java, said Indonesian National Search and Rescue Agency (Basarnas) chief Muhamad Syaugi in a live broadcast on board the Baruna Jaya, one of the vessels engaged in the search and recovery mission.
“We found the flight data recorder, (but) the cockpit voice recorder has yet to be found,” he said.
TV stations showed images of the device as it was transferred from an inflatable vessel to a ship in a large white container.
The diver who found the flight data recorder, Sertu Hendra, described how he saw the orange-coloured device buried in the muddy seabed.
“At that time I was diving at a depth of 30 metres and I also saw the wreckage of a plane measuring about one metre and a half,” he said.
Another diver told broadcaster Metro TV that he and his team dug into the seabed until they got hold of the black box. He said that he saw only "small pieces" of the aircraft, and that the search had closed in on the black box because of the "ping" signals it emitted.
Despite the name, the two black boxes - consisting of the flight data recorder and the cockpit voice recorder - are in fact bright orange with reflective stripes, and all commercial planes are required to have them on board.
The flight data recorder gathers information about the speed, altitude and direction of the plane with enough storage for 25 hours of data, while the cockpit voice recorder keeps track of conversations and other sounds in the pilots' cabin.
The treasure trove of information in black boxes helps explain nearly 90 per cent of all crashes, according to aviation experts.
Each box weighs 7kg to 10kg and can survive as deep as 6,000m underwater, or an hour at 1,100 degrees Celsius. To make them easier to find, they are fitted with a beacon which can emit a signal for one month.
"Data from the plane - the engine, all the instruments - are recorded there," said aviation analyst Dudi Sudibyo told AFP.
"If there is an anomaly, some technical problem, it is recorded there too."
It could take up to three weeks to download data from the black boxes and up to six months to analyse it, Soerjanto Tjahjono, the head of a national transport safety committee, said on Wednesday.
As part of the search operation, Indonesian authorities deployed divers, search and rescue vessels, four sonar detectors and an underwater acoustic beacon.
A "ping" sound believed to be emitted by one of the black boxes had been getting clearer, Haryo Satmiko, deputy chief of the national transport safety panel, told Reuters earlier on Thursday.
An underwater drone had detected an object suspected to be part of the fuselage, he added.
A team of divers had gone down since 5am to map the area where the black box is thought to be, Haryo said, describing sea conditions as normal.
Strong currents on Tuesday hampered the search, with the effort further complicated by the presence of energy pipelines nearby.
However, officials had said they were confident they were searching in the right area, having found items, such as life jackets, trousers and magazines, thought to be from the plane.
If found, the fuselage would be lifted using a crane, because of the many bodies likely to be trapped inside, Muhammad Syaugi, the chief of Indonesia's search and rescue agency, said on Tuesday.
Flight JT610 sped up as it suddenly lost altitude in the minutes before it disappeared, according to flight data tracking websites, with authorities saying witnesses saw the Boeing 737 Max jet plunge into the water.
Indonesian officials named the captain of the flight as Bhavye Suneja, an Indian national who had been with the airline for seven years, local media reports said.
According to Lion Air, Suneja and his co-pilot, Harvino, had 11,000 hours of flying between them and had undergone medical checkups and drug testing recently.