On Wednesday (28.11.2018) preliminary findings related to the investigation into the fatal crash of Lion Air flight JT610 were reported by investigators to Indonesian parliament. The crash, which killed all 189 people on board (including crew), occurred 13 minutes after the Boeing 737 Max took off from Soekarno-Hatta International Airport in the early morning of 29 October 2018.
It is important to emphasize that these preliminary findings are not conclusions and therefore do not pinpoint a definitive cause of the accident. However, the findings do shed some light on what happened - and what went wrong - during the flight. The findings were reported by Captain Nurcahyo Utomo, Head of the Air Accident Subcommittee of the Indonesian National Transportation Safety Committee.
Data from the Lion Air plane's black box, which was recovered from the bottom of the shallow waters off the coast of Karawang, show that the two pilots had been battling to save the airplane basically from the moment it took off. The automatic safety system repeatedly pushed the plane's nose down as it received incorrect sensor readings. If a sensor detects that the nose is pointed too high - hence possibly putting the plane into an aerodynamic stall - then the system automatically pushes the nose down.
The Lion Air pilots reacted by manually aiming the nose higher. However, they seemingly failed to detect what was causing the plane to nose down, thus did not follow the procedure for countering incorrect activation of the automated safety system. Therefore, the sequence (namely the plane's nose going down and the pilots responding by manually aiming the nose higher) was repeated about every five seconds for a total of 26 times. Eventually the machine won the battle against men as both pilots lost control of the plane. The Lion Air plane crashed into the sea at a speed of 724 kilometers per hour.
Boeing, which does not not wish to make too many statements while the investigation is ongoing, said the proper steps for pulling out of an incorrect activation of the system were already included in flight manuals.
One of the angle-of-attack sensors on the airplane's fuselage was replaced after the airplane's penultimate flight - from Bali to Jakarta - after the Lion Air plane experienced malfunctioning data readings. Investigators therefore said the plane had not been airworthy during its last two flights. However, it remains unclear whether the false data that were collected by the sensors are attributable to a problem with the sensor itself or with the computer that processes the sensors' information.
Peter Lemme, a satellite communications expert and former Boeing engineer, said he was troubled that the crew of the fatal Lion Air flight was not warned about similar problems having occurred on the previous flights, and that the Lion Air plane was not fixed after those flights.
Investigators said Lion Air needs to improve its safety culture and better document repair work on its fleet.