What Made the Indonesian Airplane Crash? New Report Sheds Mild
BANGKOK – A preliminary investigation into the Sriwijaya Air Flight 182 crash in Indonesia last month found that a difference in thrust level between the aircraft’s two engines may have contributed to the aircraft’s roll over before crashing into the Java Sea Wednesday.
As with most crashes, investigators investigate a number of factors that may have contributed to the cause. They are evaluating information from the flight data recorder and the aircraft’s maintenance records, but the seekers did not restore the cockpit voice recorder, which would tell them what the pilots said in their final minutes.
A difference in thrust level – the power of the engines that propel the aircraft forward – can make it difficult to control the aircraft. At this point it is not clear why this problem might have occurred during the Sriwijaya flight.
Many questions remain unanswered, including why the pilot and co-pilot were unable to regain control of the aircraft before it fell more than 10,000 feet in less than a minute, said Nurcahyo Utomo, chief investigator.
“What happened? We don’t know,” he said after the 31-page preliminary accident report was published by the Indonesian National Road Safety Committee. “What are the problems? We can’t answer that yet. We still cannot explain if there was an automatic throttle malfunction. “
The Boeing 737-500 crashed a few minutes after taking off on January 9 from Soekarno-Hatta International Airport in Jakarta, the Indonesian capital. All 62 people on board were killed in the crash, including six active crew members.
One focus of the investigation was the automatic throttle, a system that controls the thrust of an aircraft’s engines and is separate from the autopilot function. In the event of an auto throttle malfunction, it is typical for a pilot or co-pilot to simply turn the system off. The automatic throttle uses the data entered by the pilot to automatically regulate the two levers in the cockpit that control the thrust of the engines.
The plane’s auto-throttle system in Sriwijaya had failed twice in the weeks prior to the crash and was repaired after both incidents, according to the aircraft’s repair records.
Flight data shows that when the aircraft reached an altitude of 8,150 feet during the fatal flight, the thrust lever for the left engine was reduced while the thrust lever for the right engine remained unchanged. At 10,600 feet, the difference between the thrust from the two engines could have caused the plane to roll to the left, the report said.
Despite the aircraft’s automatic throttling issues on previous flights, Mr Nurcahyo said there was no clear evidence that it did not work on this flight. In addition, there are many airline systems that can influence the thrust of the engines.
The automatic throttle itself receives inputs from 13 aircraft components, any of which could have contributed to the problem.
“We still cannot determine why the anomaly occurred in the gas and what components caused it,” he said.
Prita Widjaja, a senior investigator on the transportation committee, said an important question was how far the lever for the left motor moved and how much the aircraft’s power was reduced.
According to international agreement, Indonesian investigators had to publish a preliminary report 30 days after the air disaster.
Because of the coronavirus pandemic, the 26-year-old aircraft had not been flown for nine months before being returned to service in December. 132 flights were made in the weeks prior to the crash. Investigators cited no evidence that the disruption contributed to the disaster.
Three days after the crash, divers recovered the aircraft’s flight data recorder, one of the so-called black boxes that records information about the mechanical operation of the jet. It provided important evidence for the investigation.
The investigation, however, was hampered by the searcher’s inability to locate the critical memory module of the other black box known as the cockpit dictaphone. This device records noises in the cockpit, e.g. B. Engine noises and conversations between pilot and copilot.
Divers retrieved most of the cockpit voice recorder, but the memory unit came loose from the case and seekers feared it was buried in a layer of seabed mud two to three feet thick. They are still looking for the module in bodies of water about 60 feet deep, but the efforts have been hampered by rough weather and poor visibility.
The relatively small size of the aircraft’s debris field – about 260 feet by 360 feet – indicates that the aircraft was intact when it hit the water and dissolved on impact, not in the air.
The Sriwijaya plane was the third to crash into the Java Sea in just over six years after departing from airports on Java, one of Indonesia’s five main islands.
In December 2014, Air Asia Flight 8501 crashed off the coast of Borneo with 162 people on board in the Java Sea as it was flying from the Indonesian city of Surabaya to Singapore. Investigators ultimately attributed the disaster to the failure of a key component of the Airbus A320-200 and an inappropriate response from the flight crew.
And in October 2018, Lion Air Flight 610 plunged into the Java Sea northeast of Jakarta with 189 on board a few minutes after taking off for Pangkal Pinang. Investigators concluded that the anti-stall system on the Boeing 737 Max, a newer model than the Boeing that crashed last month, was malfunctioning.
An Illinois law firm filed a lawsuit last month against Boeing on behalf of an Indonesian family who lost three relatives in the Sriwijaya crash. The suit claims that parts of the aircraft malfunctioned during the short flight, possibly including the automatic throttle that caused the crash.
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