MCAS: How 737 MAX system gained power and lost safeguards
So my understanding following this:<p>* they designed mcas with a g sensor and aoa sensor and a max pitch, to fix a problem in a high speed test. They provide safety assessments based on having two sensors, limited pitch changes, and it only triggering in specific rare situations.<p>* they provided that to the FAA as justification no training was needed, and that there was no need to acknowledge the existence of the system. FAA agreed.<p>* After FAA approval they discovered that the aircraft didn’t work correctly at low speed either, so they made it activate at low speed as well. Because it activated at low speed a g sensor wasn’t possible (?) so it got removed. Now you only have a single (notoriously unreliable) AoA sensor controlling it. To compensate for poor aero they also needed to increase the amount of pitch needed. So the FAA approved MCAS with a 0.6 degree pitch limit, occurring at high speed, triggered by two independent sensors. Boeing then made the system trigger at low speed, off a single sensor, and increase pitch adjustment to 2.6 degrees.<p>* Boeing <i>chose</i> not to test what happened if the AoA sensor failed.<p>* Boeing continued to insist that pilots not be made to retrain, because of contract penalties with southwest. That meant they did not want to mention the existence of the system.<p>* there safety margins also included an assumption that pilots could respond to a problem in 3s. But when mcas triggered incorrectly they were given speed, stall, and altitude warnings. All of which distracted them from the non-functioning led that indicate activation of a system that Boeing did not tell the pilots existed.<p>* the standard way to recover from the flight control computer triggering to much pitch was to flip a switch on the stick. Boeing made MCAS override that command, so the <i>standard</i> recovery could not work.<p>* Boeing continued to claim the plane was airworthy and provided a work around for its hellbent desired to crash, which was to use the manual pitch wheel. Except MCAS was designed in such a way that as part of its crash into the ground logic it put so much stress on the system that it was not physically possible for a pilot to perform the workaround.<p>In all: more than 300 people are dead because Boeing rushed to make a plane to compete with another company, and then hid information about an overriding control system so that they wouldn’t have to retrain pilots, and that completely changed the parameters of that system after FAA approval such that none of their approved safety claims were remotely true.<p>All to make some money so executives could get their bonuses.<p>Every executive who pushed for those changes should be put in jail.