The Lion Air aeroplane that crashed last month while flying from Jakarta to Pangkal Pinang – killing all 189 people on board – was deemed not airworthy on its preceding flight, according to investigators.
The full report is not expected until next year but this week’s preliminary findings will further hamper Indonesia’s attempts to restore its international reputation for aviation safety.
The Boeing 737 team struggled to control the plane after takeoff, according to Indonesia’s national transport safety committee.
Indonesian regulators have been urged after previous accidents to improve the oversight of maintenance and pilot training.
Indonesia’s director general of aviation, Polana Pramesti, said the agency planned to require the archipelago’s pilots to be trained on simulators for the Boeing MAX series.
Pramesti also said a new regulation was being planned to limit the risk of pilot fatigue and needed to be introduced in the “near future”.
On October 28, the day before the crash, the aircraft experienced technical difficulties flying from Bali to Jakarta.
The air flight maintenance log showed six issues that had been identified on the plane since October 26, including errors with its airspeed and altitude information displays.
The angle-of-attack sensor, measuring the angle between the wings and the flow of air, encountered problems and was replaced the day before the crash.
The pilots on the preceding flight should have landed rather than carrying on to Jakarta, the safety committee said.
Investigators have recovered the flight data recorder but are still hunting for the other black box – the cockpit voice recorder.
The pilots repeatedly told air-traffic control they had a problem and that they could not determine their altitude because their instruments were giving contradictory readings.
The report said the stick shaker, a warning device saying when a plane is at risk of stalling, was active throughout the flight.
This was an “un-airworthy condition” and the flight should not have continued, the preliminary findings said.
The data showed the Boeing 737 automatically tried to push the nose of the aircraft down, then the pilots were made to force the nose back up.
Investigators are asking whether faulty sensor data caused the automatic system to force the aeroplane’s nose down.
The pilot of the same plane reported similar issues the day before the crash.
After three attempts by the aircraft to automatically put its nose down, he discontinued the system and took manual control, landing in Jakarta.
The issue was addressed and reported as solved after testing.
Indonesia has a poor aviation safety record. Picture credit: Wikimedia