Investigators have called on Lion Air to improve its safety culture, after a probe into the loss of its Boeing 737 Max 8 found that pilots on the flight directly prior to the crash had continued a journey even though the aircraft was in an “un-airworthy condition”.
That 28 October flight from Denpasar to Jakarta had experienced similar technical issues to the doomed flight a day later.
Shortly after take-off, an indicated air speed disagreement message appeared on the primary flight display. The aircraft’s stick shaker was activated and remained active throughout the flight.
“This condition is considered as an un-airworthy condition and the flight shall not be continued,” said Indonesia’s National Transportation Safety Committee in its preliminary report of the crash.
A good portion of the report looked at the 28 October flight.
On that flight, the pilot flying determined that there was an issue with the left primary flight display after checks following the air speed disagreement warning. He also noticed that the aircraft would automatically trim nose down as soon as the trim input was stopped.
After three automatic nose down occurrences, the second-in-command pilot said that the control column was too heavy to hold back. The pilot then reported instrument failure to the air traffic controller and requested to maintain runway heading to Denpasar.
He then turned off the stabilizer trim switches and continued with manual trim through the end of the flight. Three non-normal checklists concerning unreliable airspeed, altitude disagreement and runaway stabilizer were performed but none called for the aircraft to land at the nearest suitable airport.
The pilot decided to continue the flight to Jakarta and made an uneventful landing. The aircraft’s stick shaker was active throughout the flight.
In the preliminary report, the NTSC recommended that Lion improve its safety culture and to enable its pilots to make proper decisions on whether to continue a flight.
The report also shows that the Max 8 had encountered repeated speed and altitude issues on the four flights prior to the deadly crash.