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Time: 2018-12-27 01:55:28 UTC

Original URL: https://www.nytimes.com/interactive/2018/12/26/world/asia/lion-air-crash-12-minutes.html [nytimes.com] using utf-8 encoding.

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How The Pilots Of Lion Air Flight 610 Lost Control

Arthur T Knackerbracket has found the following story [nytimes.com]:

Lion Air Flight 610, which took off from Indonesia on Oct. 29, should have never left the runway. On its previous flight, the aircraft gave incorrect speed and altitude readings.

But it's unclear whether the pilots were even aware that the plane had been malfunctioning. They took off at 6:20 a.m.

They immediately received the first signal that something was wrong: The control column started shaking loudly, warning that the plane was in danger of stalling and could crash.

The plane kept climbing, but the pilots could not figure out the correct altitude or airspeed, asking air traffic control for help. And two critical sensors registered different readings between the pilot and co-pilot.

Then the plane dropped over 700 feet, furthering the confusion inside the cockpit. "An aircraft dipping after takeoff is not normal. It's beyond abnormal. It's unacceptable," said Dennis Tajer, a pilot and spokesperson for the Allied Pilots Association.

Something alarming had happened: The aircraft's computer system had forced the plane's nose down. The pilots recovered from the drop, but air traffic control noted they were "experiencing a flight control problem."

Outside the plane, one of the plane's angle of attack sensors falsely indicated that the plane's nose was pointed too high, and the aircraft could stall.

This is believed to have triggered an automatic system called M.C.A.S., which pushed up the forward edge of the stabilizers on the plane's tail and forced the plane's nose down.

It's likely the pilots didn't know about this automatic system, a new addition to Boeing's 737 planes that many pilots were not made aware of. They responded by moving the stabilizers in the opposite direction, trying to lift the plane's nose back up.

This created a tug of war between the plane and the pilots — nose down, nose up — that seesawed the aircraft more than two dozen times.

In their fight against the automatic system, the pilots repeatedly held down the electric stabilizer trim switch to bring the plane's nose up. But it was only a temporary fix, and after about 10 seconds, the automatic system kicked back in.

To save the aircraft, here's what the pilots may have been able to do: disable the automatic system by flipping two switches on the center console, turning off electric control of the stabilizers, and then manually crank the wheel to right the plane.

It's likely the pilots never figured out that Boeing's new system was working against them. "Sure, it's easy to say, 'Well, just look down your trim is running away and take care of it.' That's easy to say from a desk or cubicle. Get in the cockpit, get a thousand feet above the ocean and have all those alerts going on," said Mr. Tajer.

In the final minute of the flight, things became frantic. The co-pilot told air traffic control he wanted to turn around "due to weather," possibly from clouds that may have blocked visibility. All aircraft instruments were indicating different altitudes, the pilot said.

The pilots were losing their fight against the automatic system. They pulled desperately on the control columns in a doomed attempt to level the plane, but it was too late.

The plane plunged 5,000 feet at 450 miles per hour, straight into the Java Sea. All 189 people on board were killed.

In a statement, Boeing said it was confident in the safety of the aircraft model, the 737 Max. "While we can't discuss specifics of an ongoing investigation, we have provided two updates to operators that re-emphasize existing operating procedures — the series of steps required — for these situations," the statement said.

The events on Lion Air Flight 610 were described in a report based on the aircraft's black box data released by the Indonesian National Transportation Safety Committee. The altitude data is from Flightradar24. Mika Gröndahl modeled the plane based on a three-dimensional model, photographs, Boeing diagrams and interviews with pilots. James Glanz and Allison McCann interviewed former and current pilots to understand what the Lion Air pilots may have faced. Umi Syam and Blacki Migliozzi designed and built the story.

Original Submission