Indonesian air safety investigators yesterday detailed the terrifying 11-minute roller coaster-like ride to death of the 189 passengers and crew on board Lion Air Flight JT610 last month.
Data from the ill-fated flight’s data recorder paints a picture of two Lion Air pilots locked in a pitched battle of man against machine, as they tried to wrest control of the Boeing 737 Max 8 from a ‘safety system’ out of control.
During the 11 terrifying minutes that the aircraft was airborne the malfunctioning ‘safety system’ forced the nose of the plane down some 30 times, with the two pilots repeatedly wrestling it back up, only to have the automated safety system force it back down again.
The information, contained in a preliminary report prepared by the Indonesian National Transportation Safety Committee (KNKT), suggests that the failure of a sensor was a key factor in the disaster, which resulted in the aircraft hurtling nose-first into the Java Sea at an airspeed in excess of 450 knots (725 km/h), killing all 189 people on board.
Pilots fought until the end
“The pilots fought continuously until the end of the flight”, said Narcahyo Utomo, head of the air accident subcommittee leading the crash investigation.
The report, released Wednesday November 28, revealed a sensor on the aircraft had given faulty readings in the days leading up to the fatal October 29 crash. The fault left pilots to deal with a malfunctioning Maneuvering Characteristics Augmentation System, or MCAS, that was forcing the plane into a nosedive.
Recordings from the ‘black box’ are consistent with the theory that misinformation from a faulty sensor led the automated system to point the plane in the wrong direction: down.
On previous versions of the 737 this can be overcome by pulling back on the controls. This is not the case with later models and it appears the Lion Air pilots were unaware of this. In this, they were not alone.
As early theories began to form about the cause of the Lion Air crash, pilots and airlines in the US stated that Boeing had not informed them of its new control ‘features’, and they were unaware of the sequence of steps required to disable the MCAS, should the situation arise.
As a result the US Federal Aviation Administration (FAA) issued an emergency directive to airlines in early November, telling them to update flight manuals to include instructions for how pilots can adjust flight controls under certain conditions.
Boeing: No need to detail new ‘safety feature’
Boeing has stated there was no need to detail this specific procedure for the new 737 Max 8, as proper steps for pulling out of an incorrect activation of the system were already in flight manuals. Boeing installed the MCAS in its latest generation 737 as a ‘safety feature’. The system can help prevent an aerodynamic stall by mechanically pointing the nose of the plane downward to gain airspeed.
In a statement on Tuesday Boeing said it could not comment further while the crash was under investigation.
However, CNN aviation analyst David Soucie said that the circumstances created by the plane’s automatic correction would have made pilot intervention “impossible“.
Captain Narcahyo told reporters in Jakarta on Wednesday that four of the crashed aircraft’s previous flights had experienced technical problems, with two showing no such difficulties. The plane had experienced similar problems during its previous flight from Denpasar to Jakarta, he said.
Fatal Lion Air flight not airworthy
While the committee’s preliminary report does go into analysis or draw a conclusion — nor can it be used as evidence in court — Captain Narcahyo said, “in our opinion, the plane was no longer airworthy and it should not have continued.
The MCAS had been activated on the final flight and was central to the crash investigation, he said, but it was “too early to conclude” whether the anti-stall system had contributed to the crash.
Engineers had replaced one of the two ACA sensors prior to the plane’s previous flight, but it did not correct the issue. The aircraft still showed incorrect angle-of-attack data on its penultimate flight from Denpasar to Jakarta, with an angle of discrepancy between the two sensors of 20 degrees. The discrepancy on the aircraft’s final flight was the same, 20 degrees, Captain Nurcahyo confirmed.
Soerjanto Tjahjono, head of Indonesia’s National Transportation Safety Committee, said the replacement sensor used by the budget carrier was not new, but rather a “serviceable” part certified by the FAA.
Indonesia’s largest airline, Lion Air has a chequered safety record with a number of incidents over the years. The US and the European Union have previously banned it from operating in their airspace, although both lifted that restriction in 2016.
The preliminary report from the Indonesian National Transportation Safety Committee does not go into analysis or point to what caused the tragedy.
What is known is that just after dawn on October 29 the pilots of Lion Air Flight JT610 took off from Jakarta airport in an aircraft with a known fault, and without the necessary training on how to deal with the subsequent malfunction.
Feature video TODAY
- Pilots say Boeing didn’t disclose 737 MAX plane’s new control feature that is a focus of Lion Air crash probe (ABC)
- Latest: Rescuers race to wreckage of Lion Air Flight JT610 (video) (AEC News Today)
- How Safe Are Asean Airlines? Pretty Safe Actually (Updated) (AEC News Today)
- Lion Air crash: pilot fought to keep plane in air, says report (The Guardian)
In 2009 he was Lifestyle Editor of Cambodia’s only award-winning newspaper, The Phnom Penh Post, and Deputy Editor at the launch of its weekly magazine, 7Days.
He holds a Postgraduate Diploma in Journalism and a Bachelor of Arts in Photomedia.