Boeing 737 max is the updated model of Boeing 737. Boeing 737 was a thin body aircraft while 737 max is much thick than 737 and also much more fuel efficient. So, of course it is better choice for any airlines. This aircraft was brought in to compete with another model of airbus which is a320 neo which was claimed as 15% more fuel efficient with a bigger engine.
But there was a problem. If we compare between Airbus a320 and Boeing 737(which had been upgraded later on), the Airbus model's body had much height from ground than Boeing. So Airbus could easily fit a bigger engine which Boeing couldn't. Thus they came out with an idea of uplifting the engine a bit on the wing.
Due to the change of engine placement, the CG(center of gravity) got changed which created a new problem. When 737 max is in full thrust during take off, the nose tended to point a bit up from the safe zone which could cause a stall and immediate fall down of the aircraft.
To counteract this problem, Boeing installed a software instead of re-engineering. They called it MCAS(Maneuvering Characteristics Augmentation System), which could read data from sensors and do a proper nose down in case of such situation. However, since Boeing was selling 737 max as pretty much the same plane as 737, they didn't highlight the MCAS system and flight manuals also didn't have any info on it.
Since Boeing 737 max was a better model for business, many airlines added it in their tribe. As Boeing 737 max had everything quite similar to 737, aviations didn't need to waste money behind pilots training instead pilot went through several hours i-pad training before entering into cockpit.
But Boeing didn't think, what if the sensor provide wrong data. And so happened, the Ethiopian flight 302 sensor provided malfunctioned data to macs which made MACS think that, the aircraft is in such angle of rotation which can lead a stall(Which is not true). Thus it automatically passed a nose down command to encounter the angle of rotation. The aircraft was flying on it's usual position but the nose down command passed by MACS made the aircraft nose too down and pilot wasn't able to regain the control. And it impacted the ground at around 700 MPH.
Before few months of this tragedy another 737 max crashed into java sea which was of lion air. After back to back two fatal crash in similar way, almost every country grounded Boeing 737 max. Such Behavior from an aircraft making company is not tolerable. Boeing should have mentioned there MCAS system and trained pilot properly which they didn't for which many lives has compensated.
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