Originally Posted by
PEI_3721
Re Tomaski’s post #3192, and subsequent discussions.
The points made are prefixed as ‘possible’, but subsequently argued as fact without supporting evidence.
Guilty as charged, but with reasonable grounds.
First I'd like to say that we should be careful in our use of the term "supporting evidence." Discussions on PPRuNe seem to function reasonably well with a fairly loose set of rules as to what constitutes "evidence." Most of that said evidence is actually, from a strictly legal standpoint, a bunch of hearsay, large harvested from various new agencies and online sites. If we are going to start enforcing evidentiary standards, then that standard needs to apply across the board regardless of whether one agrees or disagrees with a certain point. From my perspective, I think we are doing fine with the general understanding that the information on which we are basing these discussions are being supplied by various parties with various viewpoints, all subject to later revision. At some point we should also acknowledge that all of this information will eventually be examined and adjudicated by official agencies who actually do have to comply with rules of evidence.
Second, as you noted, each point I listed was presented without supporting evidence - to include the conclusion that Boeing really screwed this one up. I assume you are not taking issue with point #1? There is an underlying assumption that the reader has kept up with a reasonable amount of the evidence already presented and that there is no need to extensively recap this information.
Re MCAS design, from what has be been attributed to reliable description, the theory of MCAS is consistent with methods of enhancing stability shortfalls, e.g. Mach trim. However the design engineering implementation of MCAS, single system, etc, fell short of what was required or that which should have been detected - the debate goes on.
Agree
Re FAA weaknesses in oversight and certification process; most likely, but these deficiencies have been noted, investigated, and action is expected. They are central to the accidents, but apparently not unique - a continuing concern.
Agree.
Re ‘glaring deficiencies’ in operator maintenance; the scant information relating to the accidents published so far indicates that maintenance activity could be judged as good as might be expected given the lack of published information about MCAS - or of its existence at all, at that time.
In the case of Lion Air, the actual maintenance issue had nothing to do with MCAS, so it is unlikely the knowledge (or not) of this system would have made any difference. In response to a history of write-ups, maintenance personnel took several actions to include replacing the left AOA vane. This AOA vane malfunctioned from the start on the penultimate Lion Air 610 flight which seems to imply that the installation of the AOA vane was not performed correctly. This procedure is quite well known, so much so that we now have reports of an attempt to falsify photographic evidence purporting to show that the AOA work was done correctly. There is understandable debate as to what the maintenance technicians actually knew regarding the problems on this flight and whether that should have known to re-examine the AOA sensor. In any event, this aircraft was once again released into service with a faulty AOA sensor, this time with tragic results.
Re crew training relating to the accidents; no evidence provided at all. Pure supposition based on hindsight, reinforced by the ongoing debate as to how much credit should be allocated to crew intervention, alerting systems, procedures, and the apparent inability to manually move the trim from extreme positions.
First, the entire discussion regarding the state of flight crew training, and the need for improvement in various areas, can be made without a single reference to either of the MAX accidents. There have been various threads over the years, many closed, some still ongoing that have provided lots of (admittedly hearsay) testimony as to these problems. IMHO, the fact that there have not been more incidents/accidents tied to these deficiencies can largely be attributed to the multiple layers of protection built into the aviation safety system. As I stated in a separate post, I submit that the high levels of reliability and safety provided by these other areas has created a perverse incentive for airlines to cut corner on pilot training. Some of the issues regarding the crews' actions in the MAX accidents are simply another set of data points on the very long list of data points that indicate that not all is well with flight crew training.
These accidents should provide many lessons to be learnt; the first and very important is to beware hindsight bias.
By its very nature, an accident investigation tends to look back at what went wrong in the past that led to the particular event. It is much harder to look at current day actions and state with any authority that they will inevitably lead to an accident or incident. I can think a few times where I or someone I knew expressed a legitimate concern with a particular procedure only to be told that there was no data to suggest it was an issue worth worrying about (i.e. nothing bad had happened). In some of those cases, nothing bad ever did happen (well, at least not yet), and as a result nothing changed. Foresight is, at times, ineffective. What I am saying is that while hindsight does have its limitations, it does a pretty good job of identifying what should be changed in the future. Too late for those who died or suffered, but progress nonetheless.