Originally Posted by
MechEngr
That still leaves what "continuous" means. I didn't mean that it would shear the stop but that trim movement would cease when it got there and would not continue and until then the pilot would be unable to decide if it was continuous or not. Hence my leaning to what the pilots should cue on based on control forces.
I see some forces are mentioned in the Lion Air final report; sometimes the pilots were trimming when forces exceeded 65 pounds. Apparently the FO reached over 100 pounds of pull and still did not effectively trim. I expect the Ethiopian pilots were in the 60+ pound range when they stopped trimming, but until that report comes out I don't have any idea why they chose as they did. For that plane the trim forces increased only due to aerodynamic loads until they reenabled the trim motors, so how hard were they pulling before making that decision is still unknown to me.
Even the Lion Air report is not clear about why the FO accepted such high control forces except the FO had numerous training notations about difficulties in handling the aircraft which indicate to me a propensity to muscle the plane rather than use the trim switches or ask for guidance. The captain was quite proficient at handling, stopping MCAS with as little as 3 seconds of operation and almost completely reversing MCAS inputs, but didn't communicate the need for effective trimming under circumstances when such trimming was entirely unexpected.
Had there been an intermittent connection in the AND trim switch that produced similar effects to MCAS would the pilots have done the correct thing under the previous trim runaway training? Or would they still have crashed and the maker of the switches be examined and blamed for creating an untenable situation? The main difference would be no warnings at all; just a sudden and random AND trim because the AoA system would not be involved, so no stickshaker or stall warning.
Given that the NG switches were independent, but the guidance was to shut both off, probably to prevent crews from spending time trying to figure out which system was responsible and crashing the plane while making that decision or shutting off the wrong one and crashing the plane. The change in the MAX made it so that the crew could not leave a runaway source enabled no matter which switch they used. Since the plane was to be comparable to the NG there would have been the potential for confusion of a MAX pilot in an NG seat thinking only one switch was necessary, precluding the use on the MAX of only one switch even though only one was required. I do recognize I've heard of no case of trim runaway in an NG so I don't know if that compatibility would have mattered.
There have been multiple suggestions that, had the crews trained or been told of MCAS, the accidents would not have happened, but the evidence is that the only crew to successfully address it had no idea it existed and the crew that should have known every detail performed the worst of all three. Hence my feeling that instead of complex checklists to sort out trim problems, training should focus entirely on the symptoms regardless of cause. Any non-maneuvering forces should be trimmed out to allow maximum maneuvering inputs to be made. Calling out the pitch trim position following pilot input should be common so crews are fully aware of the typical values and can spot trim deviations more quickly.
PERFECT!
So how will this meet grandfather rights?