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Comment by mastercheif | Hacker News Reader

> This forward-positioning of the engine causes the nose to pitch up when accelerating quickly (and this can cause stall) and they fixed this defect using software to push the nose down.

MCAS was not intended to be an anti-stall system.

The only purpose of MCAS was to have the 737 MAX exactly mimick the 737 NG's (previous gen) pitch dynamics so that airlines wouldn't have to retrain their pilots on the 737 MAX.

Commercial pilots are generally pretty good at not stalling planes and understanding flight dynamics, they don't need MCAS to avoid stalling even when the plane pitches up during thrust.

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The biggest WTF to me is hiding the existence of this system from the pilots, even after the first crash. All in service of pretending that it’s exactly the same airplane as 737 NG.

The system was visible if the airline paid for the AOA disagree lights to be installed. Why such a basic feature was even an option is the WTF.

I can’t find anything about that. As far as I can tell, the optional AOA indicator would also include the disagree alert which would tell the pilots something is wrong with the sensors, but that had nothing do to with MCAS per se. They still had no idea there’s this whole new system that uses only one of the sensors and repeatedly trims down. Even after the first crash they only went as far as recommend going through the runaway trim procedure without explaining or even acknowledging MCAS’s existence. The pattern of omission is downright criminal.

> recommend going through the runaway trim procedure

The EA crew did not follow the runaway trim procedure sent to them in an Emergency Airworthiness Directive. The procedure is:

1. restore normal trim with the electric trim switches

2. turn off the trim system

amazing how many seem willing to overlook this fact for their narrative

would that light be sufficient in the 1:30 minutes you have to make a difference, in between the cacophony of alerts and data feeds ?

MCAS it is correcting the design defect due to put larger motors. Without MCAS that aircraft do not meets the certification requirements for to fly.

This video is about bledend-wing designs, but it touches on the 737 MAX problem with illustrations,

https://www.youtube.com/watch?v=59A8-rKRs-0&t=705s

at minute 11:45 , but it's also worth watching the part at 4:31 , where another illustration explains the forces at work in an aircraft, using a classic 737 as an example.

It is on a different subject but the whole video is very interesting.

Recent statements and speculation from FAA / EASA / Pilots suggests that the plane would've likely passed certification without MCAS: https://theaircurrent.com/aircraft-development/mcas-may-not-...

That said, it's true the MCAS was intended to address some comments from test pilots during development.

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