The pilots of a doomed Lion Air Boeing 737 MAX scoured a handbook as they struggled to understand why the jet was lurching downwards, but ran out of time before it hit the water, three people with knowledge of the cockpit voice recorder contents reportedly said.
The investigation into the crash, which killed all 189 people on board in October, has taken on new relevance as the US Federal Aviation Administration (FAA) and other regulators grounded the model last week after a second deadly accident in Ethiopia.
Investigators examining the Indonesian crash are considering how a computer ordered the plane to dive in response to data from a faulty sensor and whether the pilots had enough training to respond appropriately to the emergency, among other factors.
The captain was at the controls of Lion Air flight JT610 when the nearly new jet took off from Jakarta, and the first officer was handling the radio, according to a preliminary report issued in November. Just two minutes into the flight, the first officer reported a “flight control problem” to air traffic control and said the pilots intended to maintain an altitude of 5,000 feet, the November report said.
The captain asked the first officer to check the quick reference handbook, which contains checklists for abnormal events, the first source said. For the next nine minutes, the jet warned pilots it was in a stall and pushed the nose down in response, the report showed.
The captain fought to climb, but the computer, still incorrectly sensing a stall, continued to push the nose down using the plane’s trim system. Normally, trim adjusts an aircraft’s control surfaces to ensure it flies straight and level.
“They didn’t seem to know the trim was moving down,” the third source said. “They thought only about airspeed and altitude. That was the only thing they talked about.”
The pilots of JT610 remained calm for most of the flight, the three sources said. Near the end, the captain asked the first officer to fly while he checked the manual for a solution.
About one minute before the plane disappeared from radar, the captain asked air traffic control to clear other traffic below 3,000 feet and requested an altitude of “five thou”, or 5,000 feet, which was approved, the preliminary report said.
The flight data recorder shows the final control column inputs from the first officer were weaker than the ones made earlier by the captain.
“It is like a test where there are 100 questions and when the time is up you have only answered 75,” the third source said. “So you panic. It is a time-out condition.”
The Indian-born captain was silent at the end, all three sources said, while the Indonesian first officer said “Allahu Akbar”, or “God is greatest”, a common Arabic phrase in the majority-Muslim country that can be used to express excitement, shock, praise or distress. The plane then hit the water, killing all 189 people on board. The cause of the Lion Air crash has not been determined, but the preliminary report mentioned the Boeing system, a faulty, recently replaced sensor and the airline’s maintenance and training.