DenverTed wrote:PW100 wrote:It is not clear, but this new problem may apply also to MCAS 1.0. It could be that FAA found this issue because of extensive diligence after two accidents. Perhaps the first time aorund they (or Boeing = self-certitifying . . . ) were not so thorough in testing/validating such scenarios.
Right? Look at any skyscraper or stadium. If they inspect it or the plans long enough, there will always be flaws and code violations to be found if they look long enough.
My question is always, does this apply to the NG as well? Not that I wish for the grounding of the NG, just that if it is put under scrutiny, I'm sure there are some similar defects hiding in there. Same with the 787 or A350. The increasing complexity of the systems would take years for a second party to review. To some extent, I think that the safety is because of people getting it right the first time, and the numerous uncaught failure modes being low occurring enough that they never rear their ugly heads for 30 years of service.
Of course you will always find issues, when digging deep enough. In my mind the "Boeing falsifying records" thing may be just that. We all know that from time to time stamps get missed/forgotten on assembly records. And we all know that shouldn't happen. And we all know that it does, sometimes. And we all know that if that occurs not always the perfect world is followed (disassembly, inspect and re-assembly).
But that's in different league than missing important steps in a (D)FMEA, or FAI.
I'm not so much interested whether the failure is present in the NG, for the very simple reason that the NG has a very proven track record, and any dormant issues are so remote, that is should not be such a big deal in terms of grounding the fleet (out-of-trim manual trim wheel forces fall into that category). I think the NG is accumulating around 25M flight hours each year, and the total fleet should be closing in on 250M flight hours. Have we had any reports on the NG (let alone accidents) due to excessive manual trim wheel forces? So while the issue might still be present on the NG, the design around it, and flight ops are so good, that such a situation would occur so rarely, that it could be deemed acceptable, or at least (very) low risk
For me, it is important to understand if such issues may be present on existing MCAS (1.0), as that may put a totally different light on the claims that the accident crews did not do their thing properly (third-world-pilots / poorly trained / could not happen to american crews). If it turns out that manual electric trimming was not working, or limited in travel (to say 2.3 units stabilizer pitch), for reasons now uncovered in MCAS 2.0 testing, then a lot of folks here should be eating lots of crow. And crews all over the planet should realize that they had been very lucky not to have encountered rogue AoA . . .