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Boeing underestimated cockpit chaos on 737 Max, US investigators say

The agency’s 737 Max recommendations don’t call for any specific updates to the plane or other aircraft, but could lead to sweeping and costly changes.

The way Boeing designed its flight tests was permitted under existing rules. But the NTSB concluded those standards dating back to 1988 weren’t adequate and it called on the FAA to require more realistic assessments of complex emergencies during certification testing. Schulze said that it should be done before the Max flies again.

The FAA, regulators in other nations and Boeing have made similar conclusions in recent months about the need to ensure that average pilots can respond to complex emergencies.

The FAA said in a statement on Thursday, local time, that it would review the NTSB recommendations as it considers the proposed changes to the 737 Max: “The lessons learned from the investigations into the tragic accidents of Lion Air Flight 610 and Ethiopian Airlines Flight 302 will be a springboard to an even greater level of safety.”

Boeing said safety was its top priority. “We value the role of the NTSB in promoting aviation safety. We are committed to working with the FAA in reviewing the NTSB recommendations,” the company said in a statement.

In the 13-page report accompanying the recommendations, NTSB acknowledged Boeing was revamping the plane to prevent the same malfunction from causing another crash.

“However, we are concerned that the process used to evaluate the original design needs improvement because that process is still in use to certify current and future aircraft and system designs,” the safety board said.

Boeing is fine-tuning the plane’s flight control software and it is targeting lifting the grounding early in the fourth quarter.

The NTSB recommendations also ask the FAA to review all aircraft models to ensure that they don’t have similar safety issues lurking in the background, and to urge other nations to conduct similar reviews.

In addition, the NTSB wants the FAA to find more scientific methods to assess how pilots will perform in crises and to explore how to make aircraft warning systems more intuitive.

Both the Lion Air crash on October 29 and the Ethiopian Airlines crash on March 10 occurred after a malfunction prompted a safety feature known as the Maneuvering Characteristics Augmentation System to begin automatically and repeatedly pushing the planes into dives.


The crashes killed a total of 346 people.

While news reports following the crashes have contained some information on Boeing’s flight tests and safety assumptions about MCAS, the NTSB report is the first official account of how it was certified.

Boeing assumed that an MCAS failure had a safety risk that was “major,” which was less severe than the “catastrophic” category, the NTSB said. The company assumed pilots would easily recognise an MCAS failure and counteract it.

Boeing’s 737s, including the Max models as well as earlier versions, have a relatively simple procedure for shutting off the motor that was driving down the nose. Yet pilots in the Indonesia crash didn’t perform it and the crew in Ethiopia started the procedure and then reversed course, according to preliminary investigation reports. A third crew on a Lion Air flight the night before the crash were able to recover, but also had difficulty figuring out how to respond, the NTSB said.

“In all three flights, the pilot responses differed and did not match the assumptions of pilot responses to unintended MCAS operation on which Boeing based its hazard classifications within the safety assessment and that the FAA approved and used to ensure the design safely accommodates failures,” the NTSB said.

At least part of the reason for those mis-cues is that the underlying failure – faulty sensors that measure the angle of a plane’s nose relative to the oncoming air – triggered multiple loud alarms that were potentially confusing, the NTSB found.

In all three cases, pilots faced a thumping warning of an aerodynamic stall, indications that their airspeed and altitude gauges weren’t accurate, as well as other alerts. And that was before MCAS began activating.

However, when Boeing assessed whether the system was safe during certification, test pilots flew far simpler simulator runs. They were tested on whether they could recover if MCAS began lowering the nose without any of the additional emergencies, according to the NTSB.


“While Boeing considered the possibility of uncommanded MCAS operation as part of its functional hazard assessment, it did not evaluate all the potential alerts and indications that could accompany a failure that also resulted in uncommanded MCAS operation,” the report said.

Years of research shows that pilots can be overwhelmed during complex emergencies with multiple alarms whooping accompanied by confusing, even contradictory, cockpit indications, the report found.

While Boeing hasn’t yet responded to the NTSB’s recommendations, the initial indications are that they are receptive, Schulze said. A special review by Boeing’s board of directors on Wednesday said the company should work with airlines to “re-examine assumptions around flight-deck design and operation,” particularly given shifts in demographics and “future pilot populations.”

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