Additional problems with the Boeing 737 MAX 8 aircraft have been reported to the FAA through an anonymous tip line from current and former employees of Boeing.
Additional Safety Concerns Raised about Boeing 737 MAX 8 Aircraft
A new investigative report published this evening by Drew Griffin at CNN reveals that one day after the Ethiopian minister of transportation released a preliminary report on the crash of Ethiopian Airlines flight 302, four current and former Boeing employees called the US Federal Aviation Authority’s anonymous safety hotline to report additional problems with the aircraft.
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According to the CNN report, the four safety reports were related the MCAS autopilot system—suspected of malfunctioning and leading to two crashes of a Boeing 737 MAX 8 in a span of five months, killing all 346 people on board the two planes—and a component sensor on the outside of the plane used to measure the aircraft’s angle of attack.
The FAA confirmed to CNN that it did receive reports on their tip line and that the calls may lead to the opening of another line of investigative into Boeing’s embattled 737 MAX 8 aircraft, whose grounding around the world after Ethiopian Airlines flight 302 is entering its second month.
One whistleblower reported to the FAA that they had seen damage to the electrical wiring connected to the plane’s angle of attack sensor from a foreign object, which feeds data to the MCAS system so it can determine whether it needs to engage to prevent the plane from stalling. This wouldn’t be the first time Boeing’s manufacturing process reportedly had problems guarding plane components against foreign object debris produced by the fabrication process.
The new report of an issue with the angle of attack sensor matters because preliminary reports from the Ethiopian Airlines crash investigation shows that the angle of attack sensor was malfunctioning and sending the planes MCAS system bad data, leading the system to believe it was in danger of stalling out. Sources close to the Ethiopian Airlines investigation believe that a foreign object may have been responsible for damaging the crucial sensor.
The corrective response of the system that raises the tail of the plane also forces the nose of the plane down, and in the case of Ethiopian Airlines flight 302, the attempts by the pilots to maintain control of the aircraft during this tug of war with the MCAS system led to the crash of the plane.
The Design Decision to Only Use One Sensor Questioned
In a report last March from the Seattle Times, documents show that the Boeing safety inspectors did not fully understand or misrepresented the strength of its new MCAS system when preparing the safety review for the plane before certification.
Importantly, they did not classify the failure of this system as a catastrophic failure, the highest classification possible which indicates that such a failure would lead to the deaths of everyone on board, and assessed the consequences of failure as severe, a lower classification that does not require the system to have an additional sensor feeding data into the system.
A catastrophic failure designation would have mandated that the system not be subject to a single point of failure, but instead, use a second sensor to ensure that bad readings that could lead to failure are recognized by the system as such.
The Boeing 737 MAX 8 aircraft has two angle of attack sensors on the plane connected to the MCAS system, but inexplicably, the system was designed to take the readings from just one of the sensors. Had the system been designed to read from both sensors and compare them, a largely resource free computational operation comparatively speaking, the wildly divergent readings would have been an immediate red flag that something had gone wrong and could have prevented the MCAS from engaging.
In fact, this is one of the fixes that Boeing instituted in the wake of the preliminary report from Ethiopian Airlines, and it didn’t require retrofitting existing planes—the planes already had everything they needed for the MCAS to operate safely, these features just weren’t activated before the plane’s grounding. Had Lion Air 610’s and Ethiopian Airlines 302’s MCAS systems been programmed to compare the two data streams it was already receiving to validate the information it was getting, there’s no reason to believe that these planes would have still crashed.
Relying on a single bad sensor pushing out bad data to the MCAS has not been ruled the official cause of either crash, but coincidences like these do not just happen. The flight profiles of the two planes show the same fight to keep the nose up during take off immediately preceding the crash, and even Boeing acknowledges that the bad sensor data being fed by a single malfunctioning sensor is one link in the “chain of events” that brought these planes down.
The MCAS system in perfect working order is still a tragically flawed program. Why safety inspectors didn't designate the failure of this system as catastrophic in their certification of the plane is a question that will hopefully be answered after investigations turn up what went wrong in the process leading up to these crashes. But if it turns out that not only was the safety-critical MCAS system poorly designed but that foreign object debris produced by Boeing’s manufacturing process damage the one sensor it relied on, as suggested by the anonymous Boeing employee, then I cannot see how this situation could get any worse.