Originally Posted by
Maninthebar
I was astonished to read, in the report quoted by Grebe, that
"Boeing engineers seemed to realize they had underestimated MCAS's ability to push the plane's nose down forcefully and repeatedly, and overestimated how pilots would respond, said a person familiar with the FAA's response."
**IF TRUE** this would indicate that even Boeing didn't know how effective MCAS was.
It is also striking how often the report repeats that FAA experts struggled to understand the intricacies of MCAS, and yet continued to sanction the delivery of an AD as a risk control for a system that air crew were not being informed of nor trained for.
I suspect that no one understood how severe the trim change would be, even up to the ET302 event. Particularly at higher speeds, the pickle trim rate is a fraction of that achieved by the MCAS as presented to the crew. Had anyone on the planet comprehended that was the case, I doubt that the events would have occurred. The only people who were given a hint to that was the crew of LNI043 who coped with the problem, but still did not comprehend the implications of what they had encountered. The KNKT report discusses the crews follow up, and notes that their incident was a reportable serious incident by definition. They were the only people on the planet that had an inkling of the severity of the MCAS issue, but did not understand enough to make a cogent report that would have resulted in a more in depth investigation, a state of affairs that is more common than not. "Ground Checked Serviceable- No Fault Found" may well be correct almost all of the time, but occasionally one goes straight through the catchers mitt. When the crew reset the stab trim cutout post flight, the opportunity for anyone else to ask more in depth questions may have been lost. The engineers on the aircraft are not there to second guess the certification of the aircraft, they may on occasion recognise an issue that is well outside of the norm, and take a vigorous response, but the industry is not set up to respond in that manner. Engineers are under pressure to despatch on time, not to ponder insights on possible certification anomalies. Essentially, the industry has no real introspective process to do that, it is assumed that certification worked as advertised. We don't guess the oil feed to the turbine bearings, or inclusions on turbine disks, or lack of redundancy of a "redundant" system; to do so gets a hostile response from higher management.
We learn from bleeding.