Preliminary investigations into the Lion Air 737 Max 8 that crashed in Indonesia on 29 October have found the aircraft had “repeated speed and altitude issues”.
The report released by Indonesia’s National Transportation Safety Committee (NTSC) states that the 737 also had problems with the speed and altitude on the four flights in the three days prior before it crashed.
The NTSC has also called on Lion Air to improve its safety culture, as said that pilots on the flight directly prior to the crash had continued a journey even though the aircraft was in an “un-airworthy condition”.
The 737 crash killed 189 passengers and crew shortly after taking off from Jakarta Soekarno–Hatta International Airport, as it was heading for Pangkal Pinang in the Bangka Belitung Islands.
The NTSC report also said recordings on Flight 610’s flight maintenance log show there were issues with the left primary flight display, concerning indication of the aircraft’s speed and altitude.
The report noted the pilot of the flight directly before the 29 October crash had noted “indicated air speed and altitude disagree” and “feel differential pressure” in the aircraft’s maintenance log. He also informed an engineer about the issues and prior to that flight, an angle-of-attack sensor (AOA) had been replaced on 27 October.
The report said an engineer went on to flush the left pitot air data module as well as the static air data module to correct the speed and altitude error.
The report also said the electrical connector plug of the elevator feel computer was also cleaned to rectify the feel differential pressure. Tests were then performed on the ground, with the engineer satisfied that the issued had been resolved before dispatching the aircraft.
Data retrieved from the flight data recorder also showed that the pilots reported a “flight control problem” and had to ask air traffic control for the aircraft’s altitude and speed.
The report also said the aircraft automatically pitched nose-down more than two dozen times during the fatal 11-minute flight, with the pilots pulling the nose up each time. The automatic nose down trim stopped only when the flaps were extended, but when they were retracted it activated again. This continued before the pilots eventually lost control of the aircraft.
The report said the cockpit voice recorder has not yet been recovered.
Boeing has also released a statement on the Lion Air Flight 610 Preliminary Report and along with detailing much of what the NTSC said, it also said: “Boeing is taking every measure to fully understand all aspects of this accident, working closely with the U.S. National Transportation Safety Board as technical advisors to support the NTSC as the investigation continues.”
Boeing also said: “The report does not include records as to the installation or calibration of the new sensor, nor does the report indicate whether the sensor was new or refurbished.
“Although the report states that the pilot was satisfied by the information relayed by the engineer that the AOA sensor had been replaced and tested, on the subsequent flight the pilots again experienced problems with erroneous airspeed data, and also experienced automatic nose down trim.”
Boeing also said the report “unlike as is stated with respect to the prior flight, the report does not state whether the pilots performed the runaway stabilizer procedure or cut out the stabilizer trim switches”,
“In accordance with international protocol, all inquiries about the ongoing accident investigation must be directed to the NTSC,” Boeing also said.