Pilots struggled with flight systems in Indonesia crash

Pilots struggled with flight systems in Indonesia crash

Indonesian investigators said Wednesday that a faulty angle-of-attack indicator on a Lion Air Boeing 737 MAX 8 wasn't replaced or repaired prior to the October 29 crash into the Java Sea that killed all 189 people aboard.

Nurcahyo Utomo, an investigator for Indonesia's National Transportation Safety Commission, told reporters in Jakarta on Wednesday that four of the crashed aircraft's previous flights had experienced technical problems, with two showing no such difficulties. "In our view the plane was not airworthy".

The Boeing 737 MAX vanished from radar about 13 minutes after taking off from Jakarta on October 29, slamming into the Java Sea moments after it had asked to return to the capital.

"I think pilots can judge for themselves whether to continue", said Lion Air Managing Director Daniel Putut, a former pilot. The Airbus A320 sparked controversy after it was introduced in 1988 because it was among the first planes to have its flight functions directed via computer as opposed to stick and rudder controls.

"It's all consistent with the hypothesis of this problem with the M.C.A.S. system", said R. John Hansman Jr., a professor of aeronautics and astronautics and director of the worldwide centre for air transportation at the Massachusetts Institute of Technology.

"The fact that they fought against the MCAS (multiple) times with the trim settings was an impossible scenario to recover from", he said.

The aircraft manufacturer noted that the investigators' report cited actions by the flight crew that led to the crash.

Concerns have been raised by news that Lion Air kept putting the plane back into service despite repeatedly failing to fix the problem in the days leading up to the fatal flight.

They repeatedly told air traffic control they had a flight control problem. The flight crew's last words in response to controller's request for an appropriate altitude, were "five thou".

"The Digital Flight Data Recorder (DFDR) recorded a difference between left and right Angle of Attack (AoA) of about 20° and continued until the end of recording".

A policeman stands guard near the wreckage of Lion Air's flight JT610 at Tanjung Priok port in Jakarta
Image A policeman stands guard near the wreckage in Jakarta

The Oct. 29 struggle against the automatic system, known as the Maneuvering Characteristics Augmentation System, or MCAS, was unsuccessful.

There was a discrepancy of 20 degrees between the angle of attack readings on the side of the pilot and that of the co-pilot. Pilots of previous flights had reported problems with control systems on the brand-new jet.

Pilots who flew the aircraft before the crash told investigators that the anti-stall system engaged due to erroneous airspeed and altitude indicators, but the flight crew managed to adjust the plane's pitch manually by shutting the automated system off.

With a final crash report likely to be filed next year, the Indonesian transport safety agency has not set out a definitive cause of the accident.

Boeing's statement did not make any reference to a revised anti-stall system introduced on the 737 MAX, which U.S. pilots and Indonesian investigators say was missing from the operating manual.

"This is the basis of our recommendation to Lion Air".

Lion Air Flight JT610 plunged into the sea less than half an hour after taking off on a routine flight to Pangkal Pinang city. It added that the carrier must ensure "all the operation documents are properly filled and documented".

The preliminary report does not fully unravel the mystery behind the crash. "Every accident is a combination of events, so there is disappointment all around here", he said.

KNKT plans, among other things, to conduct aircraft simulator exercises in the Boeing engineering simulator in the United States.

Black box data released by Indonesian investigators showed that the pilots were pulling back on the control column, attempting to raise the plane's nose, with nearly 100 pounds of pressure before they crashed.

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