A faulty engine auto-throttle system that was not properly monitored by pilots led to a fatal January 2021 crash of a Sriwijaya 737-500 plane, Indonesian air accident investigator KNKT said on Thursday. in a final report.
The crash in the Java Sea after takeoff from Jakarta, which killed all 62 people on board, was Indonesia’s third major commercial plane crash in just over six years and highlighted its poor record in aviation safety.
Problems with the autothrottle system that automatically controls engine power had been reported 65 times in the 26-year-old plane’s maintenance logs since 2013 and remained unresolved prior to the crash, the agency said. agency in its 202-page report.
A functioning autothrottle is not required for an aircraft to be dispatched because pilots can manually control the thrust sticks.
However, KNKT said that in this case they did not appear to have closely monitored the asymmetric thrust situation involving the left engine throttle lever returning to as low as 34% speed after takeoff while the right lever remained. in its original climb setting at around 92%.
“There were several indications available that the pilots could have checked to identify aircraft anomalies, such as engine parameters, thrust lever position and roll angle,” the agency said, adding that complacency and confirmation bias may have been a factor in poor monitoring.
Sriwijaya did not immediately respond to a request for comment. Boeing, the maker of the 737-500 jet, declined to comment.
At approximately 10,700 feet, the autopilot disengaged and the aircraft rolled left over 45 degrees and began its plunge into the sea.
The co-pilot said “upset, upset” and “captain, captain” before the recording stopped, but the captain’s channel was not working, making it difficult for investigators to analyze the events.
A disturbed situation involves an aircraft operating outside normal flight parameters such as speed, angle or altitude.
KNKT chief investigator Nurcahyo Utomo told reporters that there had been no regulations and guidelines on disruption prevention training by Indonesian airlines that guaranteed a pilot’s ability. preventing unwanted situations from occurring, a key element being monitoring.
Sriwijaya has since provided such training to its pilots, he said.
KNKT had raised the lack of recovery training after the 2014 crash of an AirAsia Indonesia plane that killed all 162 people on board.
According to the final report, upheaval recovery training was later made mandatory in Indonesia in 2017, but Utomo said the aviation regulator failed to update the requirement after the body of the United Nations aviation agency, ICAO, said in 2018 that the course should also include upset prevention.
Indonesia is rolling out updated training on upset prevention and recovery, KNKT said in the report.