
Ask HN: Boeing 737 Max MCAS' Purpose - chupa-chups
The stated requirement resulting in the MCAS subsystem is to make the plane &quot;feel&quot; like a regular 737 &#x2F; 737NG (https:&#x2F;&#x2F;www.boeing.com&#x2F;737-max-updates&#x2F;737-max-answers&#x2F;&#x2F;#why-did-boeing-install-mcas-on-the-737-max).<p>Boeing rated MCAS as &quot;hazardous&quot; (http:&#x2F;&#x2F;www.tc.faa.gov&#x2F;its&#x2F;worldpac&#x2F;techrpt&#x2F;ar11-28.pdf, page 32, section 4 and https:&#x2F;&#x2F;www.seattletimes.com&#x2F;business&#x2F;boeing-aerospace&#x2F;failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash&#x2F;).<p>Reasoning based on the assumed competency of the pilots, reacting in only a few seconds by following the &quot;Runaway Trim&quot; checklist (https:&#x2F;&#x2F;www.wsj.com&#x2F;articles&#x2F;the-four-second-catastrophe-how-boeing-doomed-the-737-max-11565966629) they expected the usual pilots of a narrow-body plane to have quite a bit of training and experience, despite narrow-body, short-to-medium range planes are mostly piloted by not-so-experienced pilots.<p>MCAS was implemented as a system which depends on just one (known as to be unreliable) sensor (https:&#x2F;&#x2F;www.bloomberg.com&#x2F;news&#x2F;articles&#x2F;2019-04-11&#x2F;sensors-linked-to-737-crashes-vulnerable-to-failure-data-show, https:&#x2F;&#x2F;www.satcom.guru&#x2F;2018&#x2F;12&#x2F;angle-of-attack-failure-modes.html).<p>This leads to the facts:<p>* For certification, pilots need to have the same feeling as the 737NG &#x2F; 737 classic <i>in certain unusual flight conditions only</i><p>* The used (one) sensor has a comparatively high failure rate<p>* With or without MCAS, being outside of the <i>unusual flight condition</i>, the plane feels as a 737 classic&#x2F;737NG does<p>So, considering this, from my point of view, a risk supposedly most pilots could handle (different handling characteristics) was traded with a risk at least 2 pilots couldn&#x27;t handle.<p>How did Boeing come to the conclusion this is acceptable? Do you have any theories, aside from adhering to grandfathering rules set by most international FAA equivalents?
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chupa-chups
See also [https://www.satcom.guru/2019/03/regulations-around-
augmentat...](https://www.satcom.guru/2019/03/regulations-around-augmentation-
systems.html),
[http://www.b737.org.uk/mcas.htm](http://www.b737.org.uk/mcas.htm),
[https://www.satcom.guru/2019/03/regulations-around-
augmentat...](https://www.satcom.guru/2019/03/regulations-around-augmentation-
systems.html),
[http://www.b737.org.uk/mcas.htm](http://www.b737.org.uk/mcas.htm))

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peteradio
My theory is that there are idiots with power. Its pretty far out I know.

