<story><title>Ethiopian Airlines 737 MAX Investigation Preliminary Report</title><url>http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+%2C%28ET-AVJ%29.pdf/4c65422d-5e4f-4689-9c58-d7af1ee17f3e</url></story><parent_chain><item><author>dsfyu404ed</author><text>Per the article a combination of things put them in that situation.  Not just MCAS.  Why is everyone so wedded to the narrative that this is the fault of MCAS and nothing else?  Complex systems that have millions of man hours spent making them safer don&amp;#x27;t usually have back to back failures because of one faulty subsystem.  We&amp;#x27;ve incrementally refined commercial air travel to the point where single source accidents are basically nonexistent.&lt;p&gt;I&amp;#x27;m not saying that MCAS isn&amp;#x27;t mostly to blame but the fact that the maximum inputs from the pilot is still lesser than the control authority from the trim raises some serious questions MCAS or not.  Had &amp;quot;extend flaps&amp;quot; been at the bottom of the checklist that would have disabled MCAS and likely prevented this crash.</text></item><item><author>fgonzag</author><text>So MCAS put them in a hard to recover position which required electric trim to recover, and as soon as they turned on the electric trim MCAS turned on again and forced them into a crash?&lt;p&gt;Then this is much worse than initially suggested, it means a pilot can be aware of MCAS and still be put in a extremely dangerous position due to the extreme control authority of the module.</text></item><item><author>mhandley</author><text>Indeed looks like they did disable MCAS using the stabilizer trim cutout switches, but the aircraft was trimmed nose down when they did so. Aerodynamic loading prevented manual trimming using the trim wheels.  They eventually turned electric trim back on, as they didn&amp;#x27;t really have any other options, but didn&amp;#x27;t trim back enough, and left it turned on. At this point the right airspeed indicator (which should be more reliable) reads 365 knots.  VMO is 340, so they&amp;#x27;re already in big trouble.  5 seconds later, MCAS kicked back in, and then it was all over.  Very sad.</text></item></parent_chain><comment><author>fgonzag</author><text>It&amp;#x27;s true there were aggravating factors, like the inability to manually rectify trim, which (would seem to me) would be a aerodynamic or design issue.&lt;p&gt;The point still stands, the root cause was MCAS, without it this would never have happened. MCAS would not have pitched them into a dive, and even if they were pitched into a dive by some non MCAS system, they would have been able to turn on electric trim and recover. MCAS both caused the situation, and made fixing it impossible, so it was the root cause of the crash.</text></comment>
<story><title>Ethiopian Airlines 737 MAX Investigation Preliminary Report</title><url>http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+%2C%28ET-AVJ%29.pdf/4c65422d-5e4f-4689-9c58-d7af1ee17f3e</url></story><parent_chain><item><author>dsfyu404ed</author><text>Per the article a combination of things put them in that situation.  Not just MCAS.  Why is everyone so wedded to the narrative that this is the fault of MCAS and nothing else?  Complex systems that have millions of man hours spent making them safer don&amp;#x27;t usually have back to back failures because of one faulty subsystem.  We&amp;#x27;ve incrementally refined commercial air travel to the point where single source accidents are basically nonexistent.&lt;p&gt;I&amp;#x27;m not saying that MCAS isn&amp;#x27;t mostly to blame but the fact that the maximum inputs from the pilot is still lesser than the control authority from the trim raises some serious questions MCAS or not.  Had &amp;quot;extend flaps&amp;quot; been at the bottom of the checklist that would have disabled MCAS and likely prevented this crash.</text></item><item><author>fgonzag</author><text>So MCAS put them in a hard to recover position which required electric trim to recover, and as soon as they turned on the electric trim MCAS turned on again and forced them into a crash?&lt;p&gt;Then this is much worse than initially suggested, it means a pilot can be aware of MCAS and still be put in a extremely dangerous position due to the extreme control authority of the module.</text></item><item><author>mhandley</author><text>Indeed looks like they did disable MCAS using the stabilizer trim cutout switches, but the aircraft was trimmed nose down when they did so. Aerodynamic loading prevented manual trimming using the trim wheels.  They eventually turned electric trim back on, as they didn&amp;#x27;t really have any other options, but didn&amp;#x27;t trim back enough, and left it turned on. At this point the right airspeed indicator (which should be more reliable) reads 365 knots.  VMO is 340, so they&amp;#x27;re already in big trouble.  5 seconds later, MCAS kicked back in, and then it was all over.  Very sad.</text></item></parent_chain><comment><author>quenstionsasked</author><text>MCAS issues nose-down, speed increases and nose pitches down. Nose never pitches back up. Plane crashes.&lt;p&gt;Sure, maybe some complex combination of maneuvers could have helped them out of this but there&amp;#x27;s really everything pointing the blame at this one system. Pilots did what the boeing manual suggested (even included at the end of this report).</text></comment>