A defective computerized engine throttle system that was not correctly monitored by pilots led to a lethal January 2021 crash of a Sriwijaya 737-500 jet, Indonesia’s air accident investigator KNKT mentioned in a ultimate report on Thursday.
The crash into the Java Sea after take-off from Jakarta, which killed all 62 folks on board, was Indonesia’s third main industrial airplane crash in simply over six years and shone a highlight on its poor air security file.
Problems with the autothrottle system that routinely controls engine energy had been reported 65 occasions within the 26-year-old jet’s upkeep logs since 2013 and had been nonetheless unresolved earlier than the accident, the company mentioned in its 202-page report.
A working autothrottle isn’t required for a airplane to be dispatched as a result of pilots can management the thrust levers manually.
However, KNKT mentioned on this case they didn’t seem to have carefully monitored the asymmetrical thrust scenario involving the left engine throttle lever transferring again to as little as 34% pace after takeoff whereas the precise lever stayed in its unique climb setting at about 92%.
“There were several indications available that the pilots could have checked to identify the aircraft anomalies, such as engine parameters, thrust levers position, and roll angle,” the company mentioned, including that complacency and affirmation bias might have been an element within the poor monitoring.
Sriwijaya didn’t reply instantly to a request for remark. Boeing, the producer of the 737-500 jet, declined to remark.
At about 10,700 toes, the autopilot disengaged and the airplane rolled to the left greater than 45 levels and began its dive into the ocean.
The first officer mentioned “upset, upset” and “captain, captain” earlier than the recording stopped, however the captain’s channel was not working, making it harder for investigators to investigate occasions.
An upset scenario entails an plane working exterior regular flying parameters like pace, angle or altitude.
KNKT Chief Investigator Nurcahyo Utomo instructed reporters there had been no laws and pointers on upset prevention coaching by Indonesian airways that ensured a pilot’s skill to cease undesirable conditions from occurring, with a key a part of that being monitoring.
Sriwijaya has since carried out such coaching for its pilots, he mentioned.
KNKT had raised the dearth of upset restoration coaching after the 2014 crash of an AirAsia Indonesia jet that killed all 162 folks on board.
Upset restoration coaching was then mandated in Indonesia in 2017, in response to the ultimate report, however Utomo mentioned the aviation regulator didn’t replace the requirement after the UN aviation physique ICAO mentioned in 2018 the course must also embrace upset prevention.
Indonesia is putting in up to date upset prevention and restoration coaching, KNKT mentioned within the report.