CHINA AIRLINES BOEING 737 PLUNGING INTO EARTH

I cannot imagine a more terrifying ride than this one from 30,000 feet up.  Just nasty for those people....

A commenter asked me for my perspective on this.  This airplane was a 737-800 which is not the infamous 737 MAX that had two nearly identical crashes related to some bad software and system architecture that was driven by greed (read; bean counters instead of Engineering) at Boeing.  Most engineers with a conscience resent the bean counters because they throttle back on sensible design and often push cost and schedule over quality and sound engineering judgment.

Having briefly looked at the flight profile data, it looks like they had marginal control over the aircraft as it went in.  Therefore, it appears that the horizontal stabilizer was functional (or at least the elevator was).  The elevator/horizontal stabilizer was my system on all Boeing models for about a decade.  Most all models were water tight, but the 737NG (predecessor to the 737MAX) was the one with all the problems.  It came down to 60 years of changes to the legacy airframe while making few updates to the Hor Stab to accomodate those changes.  As changes to the wing were made to improve efficiencies, air flow across the wings became turbulent off the trailing edge and produced a condition called flutter in the tail feathers.  Flutter cycles the structure at a very high rate and causes it to age prematurely.  Steel is great at being able to handle high amounts of cycling, but aluminum is not so great.  The result is that the material fails prematurely and cracks and pieces depart the airplane.  While I was there, I flight tested the 737NG and we found the condition but did some minimal things to address the flutter.  But, as we chased the flutter from the elevator tab, it ended up in the elevator itself.  From there, it was chased into the Horizontal Stabilizer.  It was then chased (dampened) until it found itself into the airframe where it could dissipate or disappear.  Not a great option - but it worked.  It took a decade to sort it out without a major update to the aircraft.  The solid solution would have been to move the entire horizontal stabilizer up and away from the turbulent airflow coming off the trailing edge of the wing.  But this requires a massive change to the airframe.  Tens or hundreds of millions of dollars.  The chance for this change came when they brought in the 737MAX, because they completely redesigned the wing, the landing gear, propulsion systems, the empennage (tail feathers) and so much else.  The only thing that is remotely similar to the NG is the fuselage, whose base design goes back to the late 1950's and was adopted from the 707.  

With the MAX redesign, they moved the Hor Stab up several feet and changed the design to something more robust and aerodynamic.  Something they should have done my lifetime ago but did not have the fluid dynamics software that they have today, so they just went with what they had at the time and kept re-warming over the existing designs.  So, my guess is that the airplane either lost an elevator tab or elevator due to flutter.  It is also possible that there was a force fight between the pilot and copilot in a suicide situation.  The only way to tell if that was a situation is to see the CVR (cockpit voice recorder) or the FDR (flight data recorder) to see what inputs were given at each control column.  There is a shear mechanism between the two control columns that allows for separate inputs in the event of a control cable jam or in the case of a force fight between the two sides of the cockpit (in a suicide situation, like there was on an Egypt Air 767 a few decades ago).

So, yes in spite of this incident, I would fly on either the 737NG or the 737MAX on an airline that I know does not cut corners on maintenance and training.  Statistics show it is the safest airplane out there based on number of takeoffs and landings and flight hours/passenger miles.  The 737MAX was just fine with proper flight crew training (which Boeing opted out of to save money and avoid a new TC - Type Certificate) on the MAX, instead arguing commonality with the older 737NG.

It will be interesting to follow this case and see what comes out of it.  In the meantime, prayers for the families, knowing that their loved ones endured minutes of screaming bad terror!  Just horrible.