Principal investigator Nurcahyo Utomo said the left engine throttle lever retracted itself when the autopilot was engaged, reducing engine power before the jet plunged into the ocean. He said pilots on previous flights had reported problems with the autothrottle system on the 26-year-old jet.
The pilots’ last conversation with air traffic control took place roughly 4 minutes after takeoff, when the crew responded to the command to climb to an altitude of 5,000 meters. The plane’s flight data recorder showed it reached an altitude of 10,000 feet after which began to descend, Utomo said.
When operating on autopilot, the ability of the left engine was reduced, while the ability of the correct engine remained constant. The pilot tried to lift the plane, but it surely rolled onto its left side, Utomo said.
A minute later, the information recorder showed that the autothrottle had been disabled because the plane went down. The flight data recorder stopped recording a couple of seconds later.
“So far we do not know whether the engine throttle was damaged or not, but it surely is an anomaly since the left throttle moved significantly rearward while the correct one didn’t,” Utomo said, adding that the autothrottle movements are linked to 13 other components of the plane .
Safety committee chairman Soerjanto Tjahjono said several components were sent to the Boeing factory for further examination.
Divers managed to recuperate the crashed plane’s flight data recorder, which records a whole lot of parameters showing how the plane was operated, but were unable to search out a memory unit from the cockpit voice recorder that might tell investigators what the pilots were doing – or, failing that, regain control over the plane during a brief, erratic flight. During the collision, the module apparently separated from other parts of the recorder.
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Indonesian divers filmed the wreckage of the crashed Sriwajaya Air passenger jet on the seabed
Indonesian divers filmed the wreckage of the crashed Sriwajaya Air passenger jet on the seabed
Investigators are working with Boeing and engine manufacturer General Electric to review information from the flight data recorder. A team from the U.S. National Transportation Safety Board and the Federal Aviation Administration also joined the investigation.
The report provides latest details about persistent autothrottle problems on Sriwajaya Air’s 737-500 aircraft and the airline’s efforts to repair them. Pilots can use the autothrottle to robotically set speed, thus reducing workload and wear on the engines.
Jakarta-based aviation analyst Gerry Soejatman said autothrottle problems weren’t expected to cause the plane to crash unless they combined with other aspects since the crew could simply turn off the autothrottle.
“I am not satisfied that this accident could have been so simple. There were other factors at play,” Soejatman said. “Pilots are trained to notice this and prevent loss of control.”
Why is Indonesia the deadliest place in Asia for plane crashes?
Why is Indonesia the deadliest place in Asia for plane crashes?
Last yr, the plane was out of service for nearly nine months resulting from flight restrictions brought on by the coronavirus pandemic. Regulators and the airline said they passed inspections before industrial flights resumed in December.
The disaster renewed safety concerns in Indonesia’s aviation industry, which grew rapidly after the economy opened up following the autumn of dictator Suharto within the late Nineteen Nineties.
There have only been minor safety incidents with Sriwajaya Air prior to now, although in 2008 a farmer was killed when the plane skidded off the runway during landing resulting from a hydraulic problem.
