A defective automated 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 last 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 business aircraft crash in simply over six years and shone a highlight on its poor air security file.
Issues with the autothrottle system that robotically controls engine energy had been reported 65 instances 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 just isn’t required for a aircraft to be dispatched as a result of pilots can management the thrust levers manually.
Nevertheless, KNKT mentioned on this case they didn’t seem to have carefully monitored the asymmetrical thrust state of affairs involving the left engine throttle lever shifting again to as little as 34% velocity after takeoff whereas the best lever stayed in its unique climb setting at about 92%.
“There have been a number of indications accessible that the pilots may have checked to establish the plane anomalies, corresponding to engine parameters, thrust levers place, 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 aircraft rolled to the left greater than 45 levels and began its dive into the ocean.
The primary 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 state of affairs includes an plane working outdoors regular flying parameters like velocity, angle or altitude.
KNKT Chief Investigator Nurcahyo Utomo instructed reporters there had been no laws and tips on upset prevention coaching by Indonesian airways that ensured a pilot’s capability 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 shortage 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, based on 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 embody upset prevention.
Indonesia is setting up up to date upset prevention and restoration coaching, KNKT mentioned within the report.