Lead investigator Nurcahyo Utomo mentioned at a information convention that the pilots’ final dialog with air site visitors management was about four minutes after takeoff, once they responded to an instruction to go as much as 13,000 ft. The aircraft’s flight information recorder confirmed it reached an altitude of 10,900 ft after which started declining, Utomo mentioned.
He mentioned the aircraft required much less engine thrust because it neared its goal altitude, however that the automated throttle was unable to cut back the fitting engine’s energy due to friction within the mechanical system.
The automated throttle tried to compensate by decreasing the left engine’s energy additional, chopping its output to as little as 34%. The correct engine’s energy remained at its climb setting, or about 92%, leading to sharply unequal thrust, the report mentioned.
The pilot fought to deliver the aircraft up, however “was unable to get better from the state of affairs,” and the jet rolled onto its left facet, the report mentioned.
A minute later, the flight information recorder confirmed that the automated throttle had been disengaged because the aircraft pitched down. The recorder stopped recording just a few seconds later.
The automated throttle can be utilized by pilots to set the velocity mechanically, thereby decreasing their workload and put on on the engines. Actions of the automated throttle are linked to 13 different elements of the aircraft, the report mentioned.
Most of the issues resulting in the crash have been disclosed in a preliminary report issued by Indonesian authorities final 12 months. The ultimate report launched Thursday supplied new particulars of the pilots’ response to them.
Utomo mentioned insufficient coaching “contributed to the shortcoming of the pilot to stop and get better from the situation.”
The pilots’ overreliance on the aircraft’s automation system could have resulted in insufficient monitoring within the cockpit, in order that the flight deviation was not instantly observed, the report mentioned.
Utomo mentioned the voice information recorder solely labored on one audio channel, and one other channel that was speculated to report all voices within the cockpit was full of an unknown buzzing sound that prevented investigators from totally analyzing the coordination between the 2 pilots.
The report concluded that repeated makes an attempt to restore the automated throttle over time had failed as a result of they’d not correctly fastened the mechanical subject.
Investigators labored with Boeing and engine maker Common Electrical to evaluation info from the flight information recorder. A staff from the U.S. Nationwide Transportation Security Board and Federal Aviation Administration additionally joined the investigation.
The aircraft had been out of service for nearly 9 months due to flight cutbacks attributable to the coronavirus pandemic. Regulators and the airline mentioned it underwent inspections earlier than resuming business flights in December 2020.
The catastrophe reignited considerations about security in Indonesia’s aviation business, which expanded rapidly after the nation’s financial system was opened up following the autumn of dictator Suharto within the late 1990s. The USA banned Indonesian airways from working there in 2007 however lifted the measure in 2016, citing enhancements in compliance with worldwide aviation requirements. The European Union lifted the same ban in 2018.
Sriwijaya Air, an Indonesian home airline based in 2003, has had solely minor security incidents prior to now, although a farmer was killed in 2008 when a aircraft went off the runway whereas touchdown attributable to a hydraulic subject.
In 2018, a Boeing 737 MAX eight jet operated by Indonesia’s Lion Air crashed, killing 189 folks. An automatic flight management system performed a task in that crash, however the Sriwijaya Air jet didn’t have that system on board.