Boeing admitted that they discovered an error that disabled a safety feature on their 737 Max planes in 2017 but didn’t notify airlines or regulators until the Lion Air crash in Oct. 2018.

Safety was optional

The safety indicator is called “Angle of Attack Disagree Alert” and it’s supposed to warn pilots if the sensors are sending contradicting data about the angle of the plane’s nose. Boeing found out the indicator only worked on planes that had premium options, which meant about 80% of 737 Maxes were left with faulty safety systems. However, Boeing still didn’t let the airlines know.

Neither Lion Air nor Ethiopian Air had working AOA Disagree Alerts on their 737 Max fleets.

Doomed from the start

According to a report by The Verge:

  • The 737 Max is Boeing’s best selling plane to date (over $200 billion worth sold), which means you’ve probably flown on one of them.
  • Boeing rushed the Max to catch up on its chief rival Airbus A320 Neo, which boasted superior fuel efficiency and was eating up Boeing’s market share.
  • Instead of spending time and $ to develop an entirely new plane, Boeing cut corners by slapping a bunch of new techs on an old frame that came out in…1964.

All of this resulted in a fundamentally flawed design. Boeing wanted to put larger engines on the Max but couldn’t find enough space underneath the wings to attach them. So they just moved the engines forward and placed them higher on the wings.

This modification caused a serious aerodynamic problem – the size and position of the engines lifted the plane higher and made it handle differently than previous 737 models.

Boeing being Boeing, they added a complicated software called MCAS that would pull down the nose of the plane in case of steep climbs instead of fixing the issue fundamentally. Moreover, to promote the Max to airlines as an easy-to-learn model, Boeing didn’t even mention the new software in the manual. Instead, the company told pilots they would need just a 2.5 hour iPad session to learn how to fly the new plane.

Then came the crashes

Both the Lion Air and Ethiopian Airlines crashes were caused by MCAS malfunctions. Sensor errors fed MCAS false data which made the software force down the planes to the ground.

The pilots in both crashes didn’t even know what MCAS was, much less how to control it – because…Boeing didn’t put it in the manual.

More crucially, if the pilots had functioning AOA Disagree Alerts, they would’ve learned about the sensor errors earlier and had more time to manually control the planes.

Software fixes to hardware problems, again.

Boeing maintains that the AOA Disagree Alert error “did not adversely impact airplane safety or operation”.

Boeing hopes to get the grounded Maxes flying again by this summer. Their fix? software updates to MCAS and AOA Disagree Alerts.


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