Boeing cites airline error in Indonesian crash

Graphic showing the location of the plane crash

Graphic showing the location of the plane crash

However, it does not give a definitive cause for the accident.

The aircraft maintenance log shows that since Oct 26, there had been six reports of problems, including faulty sensor readings.

Although the crew appears to have squawked the problem, the NTSC reports that maintenance was done on other components, but apparently not the AoA sensor, although press reports differ on this finding.

The crew said that the aircraft was operating in abnormal conditions due to instrument failure.

The malfunctions and warnings from the plane's control system appeared to overwhelm the pilots nearly as soon as the jet became airborne, said another investigator, Ony Suryo Wibowo. "A lot" could be attained by investigators from the voice recorder, Utomo said. For instance, it is known that an AOA sensor was replaced before the flight preceding JT610.

JT610 departed from Jakarta airport on runway 25L, at 06:20 local time on 29 October / 23:20 GMT on 28 October.

The preliminary report does not fully unravel the mystery behind the crash.

The sensor, called an angle-of-attack vane, or AOA, malfunctioned in earlier flights. "This condition is considered as un-airworthy condition and the flight shall not be continued", the report states.

The report said that the plane was "automatically trimming" on the previous flight - that is, the computer was adjusting the aircraft's angle - so the pilots switched to manual trim and, as their safety checklists didn't recommend an emergency landing, they continued to Jakarta.

Within 90 seconds of takeoff, the co-pilot asked air traffic control to confirm air speed and altitude. The controller approves this request. After recovering from a sudden drop in altitude, the pilots struggled to maintain level flight after passing 3,000 feet, before the aircraft went into a deep dive just over 10 minutes after take-off. Those adjustments would push the nose of the aircraft down to increase the lift generated by the wings with a combination of improved air flow over the wings and increased airspeed.

Utomo faulted Lion Air's maintenance and safety culture in the crash, though a final finding on the cause of the crash is likely months away.

Indonesia Lion Air Crash
Members of the National Transportation Safety Committee lift a box containing the flight data recorder

MR NURCAHYO UTOMO, sub-committee head for air accidents at Indonesia's National Transport Safety Committee.

Boeing 737-MAXs contain automated systems to prevent an aircraft stalling if its nose is too high.

The system was responding to faulty data, which suggested that the nose was tilted at a higher angle than it was, indicating the plane was at risk of stalling.

After the crash, Lion Air instructed pilots to provide a "full comprehensive description" of technical defects to the engineering team, KNKT said.

As our customers and their passengers continue to fly the 737 MAX to hundreds of destinations around the world every day, they have our assurance that the 737 MAX is as safe as any airplane that has ever flown the skies.

The plane experienced technical problems in four earlier flights.

If the automatic system kicked in and "the pilot didn't know what was happening", there was a risk it would confuse the pilots, he added.

The Lion Air plane that crashed into the sea was "no longer airworthy", Indonesian officials said.

It also told the airline to improve its documentation, pointing out that while there were six flight attendants on the flight, Lion Air's record showed that there were only five on board.

"I think pilots can judge for themselves whether to continue", said Lion Air Managing Director Daniel Putut, a former pilot.

Lion Air, Indonesia's largest airline, has a notoriously bad safety record. Because the MAX aircraft have heavier engines, the center of gravity is biased more forward than on previous models and MCAS is meant to improve pitch feel and provide stall protection.

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