Lion Air pilots struggled to maintain control of their Boeing jet as an automatic safety system in the plane repeatedly pushed the plane’s nose down, according to a draft of a preliminary report by Indonesian officials looking into last month’s deadly crash.
Investigators are focusing on whether faulty information from sensors led the plane’s system to force the nose down.
The new Boeing 737 MAX 8 plunged into the Java Sea on October 29, killing all 189 people on board.
The New York Times reported that information from the Lion Air jet’s flight data recorder was included in a briefing for the Indonesian parliament and reported by Indonesian media.
Indonesia: ‘No survivors’ after Lion Air flight crashes into sea
Indonesian authorities are expected to release their preliminary findings later on Wednesday, although it is unclear whether they will offer a probable cause for the crash.
The MAX 8, the latest version of Boeing’s popular 737 aircraft, includes an automated system that pushes the nose down if a sensor detects it is pointed so high the plane is at risk of an aerodynamic stall.
‘Deadly game of tag’
Peter Lemme, an expert in aviation and satellite communications and a former Boeing engineer, described “a deadly game of tag” in which the plane pointed down, the pilots countered by manually aiming the nose higher, only for the sequence to repeat about five seconds later.
That happened 26 times, but pilots failed to recognise what was happening and follow the known procedure for countering incorrect activation of the automated safety system, Lemme told The Associated Press.
He said he was also troubled that there weren’t easy checks to see if sensor information was correct, that the crew of the fatal flight apparently wasn’t warned that similar problems had occurred on previous flights, and the Lion Air plane wasn’t fixed after those flights.
“Had they fixed the airplane, we would not have had the accident,” he said. “Every accident is a combination of events so there is disappointment all around here.”
Boeing did not immediately respond to requests for comment.
The company said last week it remains confident in the safety of the 737 MAX and had given airlines around the world two updates to “re-emphasise existing procedures for these situations”. The US regulator has also issued a directive on the MAX 8 and 9 models.
More than 200 MAX jets have been delivered to airlines around the world.
The investigation is continuing with help from US regulators and Boeing.
The plane’s cockpit voice recorder, which would provide more information about what happened in the cockpit, has yet to be found.