Yo
gums,
‘…
still looking for the aero explanation that is more relevant than basic control column feel.’
Ethiopian airliner down in Africa
Ethiopian airliner down in Africa
Nothing more specific to add; no detailed knowledge or reasoning in the public domain.
I suspect that the aerodynamic issue caught Boeing by surprise - late in flight testing; the existence or extent of change of pitching moment (stick force stability), its origin - engine nacelle, nacelle / wing interaction. Possibly a judgement that the handling characteristics would be ‘good enough’ - FAA association.
The need for modification - increased stick force to meet stability requirements at a few specific points in the flight envelope could be achieved with a range alternative approaches; hardware fixes - cf Mach trim, STS, feel shift. These progressively require ‘controlling’ parameters best achieved with software, thence use of ‘full’ software, but it wasn’t ‘full’ or comprehensively protected - faster, better, cheaper; NASA got that wrong; how we fail to learn, how quickly we forget.
The comparisons with modern FBY wire systems and the aerodynamics of those aircraft, adds little to this debate. The 737 airframe and systems design are very old, progressively enhanced, adapted to market demand - with the perception of new shiny technologies are better, at least cheaper.
A more suitable comparison would be with the 707 / 727; in my case the Comet. I recall that the Comet, or its derivatives had a ‘pitch gear change’, (not a manual shift), a smooth electrical repositioning of a mechanical cam which changed the ratio of stick to elevator (also used in the Sea Vixen to cope with transonic trim change). The need for Mach trim in commercial aircraft emerged as speeds increased (stability, stick force reversal), but due to its novelty, solutions were carefully thought through with reliable implementation.
The recent events will go down in history. History, as with war crimes, is written by the victors (lawyers, politicians).
The most important aspect for the industry is in what we learn, how this is to be learnt and implemented. The issues with certification processes may dominate - how to certificate modern systems, common standards, international approval, … trust.
The industry is transitioning from the generally knowable, to more uncertainty. How do we manage aircraft and people in an uncertain world.
https://www.farnamstreetblog.com/201...r-uncertainty/ (Three parts linked)
FAA / Boeing could reconsider their relationship with ICAO, aviation language, safety culture.
More Integration opposed to dominating Assimilation:-
https://www.dropbox.com/s/7425e8yykg...20%2B.pdf?dl=0 (use website option)