JAKARTA: Indonesia’s National Transportation Safety Committee said on Wednesday (Feb 10) that investigations into Sriwijaya Air SJ 182 that crashed last month would focus on the plane's autothrottle system.
Preliminary investigations showed that the system, which controls engine power automatically, could have malfunctioned.
In a press conference to announce its preliminary report, the committee's aviation head Nurcahyo Utomo said both autothrottles of the plane showed anomalies.
"For the left one, the retreat was too far, while the right one didn't move, so it was stuck. We don't know which one was broken, the left or the right one," he added.
Mr Utomo added that the investigation would focus on the plane's autothrottle system and related components installed in the aircraft, the plane's maintenance record as well as possible human factors involved.
READ: Sriwijaya Air crash: Co-pilot among the brightest at flying school, pilot a 'warm and compassionate' person
The Sriwijaya Air plane took off from Jakarta on Jan 9 and was en route to Pontianak, West Kalimantan when it disappeared from radar screens just four minutes after take-off.
Air traffic control at Jakarta’s Soekarno-Hatta International Airport asked the pilot just seconds before it disappeared why it was heading northwest instead of on its expected flight path but never received a response.
Authorities concluded the plane crashed into the Java Sea leaving no survivors. All 62 people on board died.
The Flight Data Recorder of the ill-fated flight has been retrieved, but authorities are still searching for the missing Cockpit Voice Recorder which could shed light on what really happened.
The Boeing 737-500 plane was nearly 27-year-old.
AUTOTHROTTLE SYSTEM REPAIRED DAYS BEFORE JAN 9
In Wednesday's press conference, Mr Utomo also revealed that the plane's autothrottle was broken prior to Jan 9, but had been repaired.
"On Jan 3, 2021, the pilot (of a previous flight) reported that the autothrottle was unserviceable. The engineer rectified the problem by cleaning the autothrottle computer’s electrical connector. After reinstallation, the Built-in Test Equipment (BITE) test result was good.
"On Jan 4, 2021, the pilot reported that the autothrottle was unserviceable. The engineer tried cleaning the autothrottle computer’s electrical connector but the problem remained."
An engineer rectified the problem the next day and the BITE test showed it was good, Mr Utomo added.
"After Jan 5, there were no more DMI (Deferred Maintenance Items) records in the aircraft maintenance log until the date of the accident, Jan 9, 2021," he said.
Apart from the autothrottle, the plane had problems on Dec 25 with the first officer's airspeed indicator but it was replaced on Jan 4.
The preliminary investigation also showed that the plane's autopilot was disengaged.
The plane did not go through areas with significant clouds, rain or in-cloud turbulence.