Issues with the aircraft’s automatic throttle system were reported 65 times from 2013 up to the time of the disaster.
A faulty automatic engine throttle system that was not properly monitored by pilots led to the January 2021 crash of a Sriwijaya Air Boeing Co 737-500 airliner, Indonesia’s air accident investigator, KNKT, has said in a final report on the accident.
The jet crashed into the Java Sea shortly after takeoff from the Indonesian capital Jakarta, killing all 62 people on board, becoming the country’s third key commercial plane crash in just over six years.
KNKT said in its 202-page report released on Thursday that problems with the automatic throttle system that controls engine power had been reported 65 times in the doomed aircraft’s maintenance logs from 2013 onwards, and were still unresolved at the time of the accident in 2021.
Sriwijaya did not respond immediately to a request for comment. Boeing, the manufacturer of the 737-500 jet, declined to comment.
Starting with just one plane in 2003, Sriwijaya Air became Indonesia’s third-largest airline group, aided by its strategy of acquiring old planes at cheap prices and serving secondary routes neglected by larger airline competitors.
According to the accident report, at about 10,700 feet (3,260 metres), the autopilot disengaged and the plane rolled to the left more than 45 degrees and started its dive into the sea.
The first officer said “upset, upset” and “captain, captain” before the recording stopped, but the captain’s channel was not working, making it more difficult for investigators to analyse events. An “upset” situation involves an aircraft operating outside normal flying parameters such as speed, angle or altitude.
KNKT Chief Investigator Nurcahyo Utomo told reporters there had been no regulations and guidelines on upset-prevention training by Indonesian airlines that would have ensured a pilot’s ability to stop unwanted situations from occurring, with a key part of that being monitoring.
Sriwijaya has since carried out such training for its pilots, he said.
KNKT had raised the lack of upset recovery training after the 2014 crash of an AirAsia Indonesia jet that killed all 162 people on board.
Indonesia is putting in place updated upset prevention and recovery training, KNKT said in the report.