By Prarthana Mitra
A month after Lion Air’s fatal crash into the Java Sea, the black box data revealed that pilots struggled to maintain control of the jet after its automatic “anti-stall” safety system repeatedly pushed the plane’s nose down 26 times.
Despite stressing that this preliminary report did not give a definitive cause, aviation head of the Indonesian investigative agency has claimed that the Boeing jet, which caused nearly 200 casualties, was not airworthy and should have been grounded.
Here’s what happened
The new Boeing 737 MAX 8 crashed into the Java Sea on October 29, killing all 189 people on board, including Indian pilot Bhavya Suneja.
According to a draft of the preliminary report submitted by Indonesian National Transport Safety Committee (KNKT) on Wednesday, faulty sensors on the plane’s system are believed to have caused this anomalous automatic response, which ultimately led to the nosedive.
The report also claims that the jet began to experience “stick shaker activation”, which vibrates the pilot’s controls, immediately after takeoff. Furthermore, the jet had experienced airspeed and altitude issues in four different flights in days leading up to the crash, and had erroneous sensor readings several times, making it “un-airworthy”.
The report also discusses Lion Air’s maintenance practices and the anti-stall system in the aircraft.
What could have gone wrong?
The preliminary report suggests that the anti-stall system received incorrect information from sensors on the fuselage. The pilots attempted to correct it more than two dozen times, but ultimately lost control of the plane and it plummeted into the ocean at 450 miles per hour.
The pilots appeared to struggle with an automated system designed to keep the plane from stalling a new feature in the 737 Max family. The new manoeuvring characteristics augmentation system (MCAS) is “a computerized system Boeing installed on its latest generation of 737 to prevent the plane’s nose from getting too high,” according to the New York Times.
Peter Lemme, an aviation expert and former engineer at Boeing, described the final few minutes in the Lion Air cockpit as “a deadly game of tag”. He explained, every time the plane pointed downward, pilots would manually aim it higher using their controls, only for the sequence to repeat about five seconds later.
Who is to blame?
This is particularly worrisome for Boeing because even after similar problems had occurred on previous flights, the Lion Air jet hadn’t been fixed. It is further unacceptable that the crew of the flight were not warned of this possibility.
In the aftermath of the crash, many airlines and pilots have complained that the pilots have not been trained by Boeing on how to operate the critical new flight control system on the new 737 Max, even though the jets have been dispatched and are flying all over the world. It is not clear yet if the Lion Air pilots aboard flight JT610 knew of the manual overriding procedures.
“Had they fixed the airplane, we would not have had the accident,” Lemme further told Reuters. “Every accident is a combination of events, so there is disappointment all around here,” he said.
What happens next?
Boeing hasn’t responded to these latest revelations, although they issued a statement last week about sending out two urgent updates to the airlines about the “existing procedures for these situations“.
Information from the Lion Air jet’s flight data recorder was a part of the briefing for the Indonesian Parliament. Search parties haven’t retrieved the plane’s cockpit voice recorder yet, which could shed more light on the pilots’ actions. Indonesian authorities released the findings on the condition that no definite conclusions would be drawn from the data immediately. Meanwhile, the investigation in Jakarta continues with assistance from US regulators and Boeing.
Prarthana Mitra is a staff writer at Qrius