[gtr32x]

I've always been confused here on this, does that mean the 737 MAX has a high chance to have faulty reading from their AoA sensors? Or is that pretty much the industry standard right now? This has always seem like the actual culprit.

[azernik]

Sensors break. They get gunk on them. They ice over.

Generally a sensor with such a critical failure mode would be triple-redundant - if one fails, the discrepancy between sensors is flagged and the aircraft runs on the other two until the broken one is fixed. In this case, the aircraft had two sensors of the type (Angle-of-Attack), but MCAS was only listening to one of them.

[pas]

How does this AoA sensor works? I'm guessing it has to sense the direction of the wind and then calculate the vector of the wings compared to that?

I've seen pictures of it ( https://aviation.stackexchange.com/questions/2317/how-does-a... ) and seems to be a simple mechanical component.

Why isn't this compounded with something that works by estimating the AoA from other factors? A few simple gravity based sensors would be able to tell the vector of the plane, and simply assuming that wind (airflow) is parallel to the ground would go a long way. Or is the vertical component of the local airflow so variable?

[gtr32x]

Thanks for the elaboration. Could you help me further understand one more thing? When you say MCAS only listens to one, does that mean during the time when one AoA sensor fails? Or it always listens to one during normal operation?

Also, it does seem like Boeing dropped the ball here to not build further redundancy here.

[kjar]

The lack of redundancy by default coupled with extreme profit seeking by Boeing for the 'upgrade' is inexcusable. TL;DR They shit out a faulty product hundreds died as a result

[dingaling]

> Or is that pretty much the industry standard right now

Half the industry uses three or four AoA sensors with majority voting.

The other half ( Boeing ) uses two.

[londons_explore]

Even redundancy doesn't really solve the issue. The sensors are out in the same environmental conditions, so will likely all fail at once, for example a bad pattern of water followed by cold causing icing.

Instead, the sensors should detect failure, for example by using a motor to detect if the vane is stuck and cannot turn freely.

The flight controls should also be able to fly even if all sensors of a certain type have failled. Angle of attack for example can be approximated with an accelerometer and gyro well enough to keep the plane in the air.