Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark

In a mostly-robust system, different layers catch and defend against the errors of other layers in the system. For a major accident to occur, holes in multiple layers have to line up that day.

In this case we have four holes that lined up that day - a plane model with a possible rare software bug, an aircraft with a faulty sensor feeding bad information to the computers, an airline company with internal culture that continues to fly a specific aircraft that keeps trying to point at the ground, sometimes without even making an attempt at fixing the problem, and finally, on this fatal day, a crew that did not follow the proper procedures even after twenty-three nose down incidents during the flight.

Even without the MACS system present, the last two holes seem like they would bring down an airliner eventually, from one cause or another.

Pilots are rightfully mad about not being told about the MACS system. But it's just one of many systems on a 737 that can trim the stabilizer to point that it can't be flow. That's why the procedure for any stabilizer problem is to disable automatic control of the stabilizer. The training and checklists that the accident pilots had covered this, and previous pilots flying the accident aircraft did this and then had uneventful flights.

Imagine that the failure that caused the nose-down wasn't a failed AOA sensor giving bad readings to MCAS, but some other reason that _also_ wouldn't have been solved by pulling back on the yoke, but would have been by completing some later step on the checklist. Suppose the pilots didn't follow the checklist. Would that be enough information to say that Boeing is responsible?

To be sure, in this case the pilots may have followed the checklist! It may well be the case that Boeing is completely responsible! The checklist items might not have worked, or there may have been a good reason that the pilots didn't follow it, or the checklist might have been crazy, or they might not have had time to do what needed to be done, etc. There's still a whole lot that's not known (or hasn't been released) about what happened.

I'm just not sure that the current evidence, _viz_ that Boeing made an internal software change, that they didn't explicitly call it out to pilots, and that there's no difference in the actions prescribed in the event of an uncommanded nose-down pre- and post-change, is enough to say that the fault is entirely Boeing's for this accident.

Absolutely reasonable to ask what Boeing could have done better. I'm just not sure the information about Boeing's actions contained in the article gets me all the way to "indefensible", paraphrasing another comment.

And you are writing this after many, many accidents that root cause was pilot not exactly knowing what or why something happens with a plane or plane autopilot (ie. AF 447)

Being apologetic of cost cutting on safety issues is dumb as it erodes culture of safety and encourages others to skimp on safety.

Pilots are pretty unhappy about this M.C.A.S. situation. They're literally expected to fly an aircraft, and not even being told how that aircraft functions. And while the checklist may eventually take care of this, that isn't a substitute for a professional pilot in the cockpit. Just the lack of training/simulated failures for this new system is highly irregular, pilots are used to and expect such training while transitioning to a new major aircraft version.

The biggest drivers here seem to be cost and Boeing's competitiveness, not safety. I think it might be time for the EASA to trust the FAA a little less, at least until they get their house back in order.