The flight data recorder of Lion Air Flight JT610 was retrieved in good condition yesterday, raising hopes that it could help establish why the nearly brand new plane crashed just minutes after take-off.
Navy divers found the device at a depth of around 30m in the waters off Karawang, West Java, three days after the plane plunged into the Java Sea about 13 minutes after taking off from Jakarta en route to Pangkal Pinang city.
The team also recovered a large object - 1.5m in length and half a metre in width - suspected to be part of the fuselage of the Boeing 737 Max 8 plane, said Indonesia's National Search and Rescue Agency (Basarnas) chief Muhammad Syaugi.
Deputy chief of the National Transportation Safety Committee (KNKT), Mr Haryo Satmiko, confirmed that the flight data recorder is in a good condition, saying the data will help the investigation into the aircraft as well as the crew.
"With this black box, we want to clarify our findings on the ground," Mr Haryo told Kompas TV.
The flight data recorder and the cockpit voice recorder, both known as the black boxes, could provide clues on the events leading up to an incident. The search for the cockpit voice recorder is ongoing.
Mr Haryo said the flight data recorder covers up to a 25-hour flight history of domestic flights by the plane, including the flight from Denpasar on Bali Island to Jakarta the night before the accident.
Veteran pilot Byron Bailey said the flight data recorder was the more crucial piece of the puzzle.
"This is the one they really need as it will reveal all indications or parameters of flight and control inputs, plus the flight path," he said.
Aviation expert Alvin Lie believed the black box would likely be functioning well. "That it was found so early will help a lot in figuring out what happened to the plane that crashed," he said.
The recovery was relatively quick compared with past incidents. The black boxes of Air Asia QZ8501, which crashed into the Java Sea en route from Surabaya to Singapore on Dec 24, 2014, and killed 162, were found after 16 days of searching.
Although the flight data recorder of the Lion Air plane was recovered quickly, aviation experts and investigators cautioned that this is just the start of a long process. A full analysis of a plane crash usually takes from several months up to a year. The report on the Air Asia flight crash was out nearly a year later.
A complete study to determine the cause of the crash based on the black boxes may take up to six months, according to KNKT, which has a one-year deadline to do so.
Before the study is out, the committee will publish a preliminary report - containing facts such as weather records and pilot qualifications - within one month.
One of the crucial issues that investigators seek to address is why the pilot requested to return to base just minutes after take-off, to which air controllers granted permission. The plane with 189 people on board vanished from radar about 10 minutes later.
KNKT had earlier said the plane encountered a problem during its previous flight, but Lion Air chief executive Edward Sirait claimed that the issue was already resolved and the plane was declared fit to fly.
Transportation Minister Budi Karya Sumadi on Wednesday ordered Lion Air to temporarily discharge its technical director and several engineers in charge of the aircraft operation.
He said the Transportation Ministry will review all regulations concerning aviation safety, as instructed by President Joko Widodo. It will also assess the possibility of raising the ticket prices for flights run by low-cost carriers.
Meanwhile, the search and rescue operation entered the fourth day yesterday, while police forensic experts continued their painstaking process to identify the remains of the bodies recovered.
As many as 61 body bags have been received so far, based on latest figures from Basarnas. As of yesterday, only one passenger, civil servant Jannatun Cyntia Dewi, had been identified.
"Some family members have accepted (the situation). Others still have not come to terms with it," said National Police Hospital director Musyafak.