Reply to post: Re: Say, what?

Boeing admits 737 Max sims didn't accurately reproduce what flying without MCAS was like

lowwall

Re: Say, what?

Excessive Angle of Attack results in an aerodynamic stall, not an engine stall. An aerodynamic stall means there is not enough airflow over the wings to support flight, so down you go. This normally occurs when the nose of the plane is held too high for the engines to maintain airspeed. A stall is normally a recoverable event as long as you have enough altitude. If the plane is level and center of gravity is where it should be, it's actually a non-issue. The nose will drop and once you speed up a bit from falling, there will be enough airflow over the wing for it to start flying again. The Airbus crash over the south Atlantic a few years ago was caused by the computers putting the plane into an aerodynamic stall (due to faulty incoming data from iced over air pressure ports) which the co-pilot (who had command of the controls once the autopilot shut off) exacerbated by holding the stick back until it was too late to recover.

But this isn't what caused the Max crashes, it was actually an attempt to avoid the above scenario in the first place that did it. The issue on the 737 Max is the engines are mounted further forward than normal. At high power levels (for example during takeoff), this tends to pitch the nose up more than pilots are used to which could eventually result in a stall if allowed to continue. MCAS was designed to counter this by automagically trimming the tail to lower the nose when it detected the nose was too high. In both flights, it appears that a faulty AoA sensor resulted in MCAS repeatedly applying the trim when it wasn't needed. Poor software choices and inadequate training resulted in 2 planes diving into the ground while the crews tried to figure out what was going on.

Note: depending on how many other engines you have, an engine stall means you are either flying a glider or have reduced power. But the plane is still under aerodynamic control. Sully's "Miracle on the Hudson" along with millions of other successful glider and engine out landings tell us that an engine stall is not a death sentence, just an issue to be handled.

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