Yo gums, ‘a sim is just a … ‘ until it isn’t.
A common difficulty in simulation is the friction associated with conventional cable runs, cranks, pulleys, etc and how they change with in-flight loads.
This could be major issue in the simulation of manual trim-wheel operation, even more so if the stabiliser forces were so excessive that they prevent trim wheel movement - see discussions https://www.pprune.org/tech-log/6193...izer-trim.html

Re ‘a good idea’ demonstrating the malfunction: given the current level of knowledge, unknowns, variables; then the flight test planning might judge the need to roll the aircraft towards the inverted so to use the adverse trim condition to affect ‘upwardness’, then unload-load the elevators, and move the trim wheel.

Easy in your Viper, not such a good idea for a commercial aircraft flight test. ;)

from a fellow in Airliners.net
quote:
I'm beginning to picture this scenario:

• * you have a malfunctioning AOA sensor, which basically by random misfortune happens to be the one feeding STS and MCAS for this flight (the other one works just fine, but is being ignored)
  * you get no warning of the failure, because your cheap-o third-world airline did not purchase the AOA disagree warning option
  * instead, you get stick shaker and stall warning
  * so you push a bit of nose down (and perhaps add a little thrust) to build a safety speed margin above an airspeed you're suddenly no longer sure about
  * MCAS - which you may or may not know about, certainly not through reading the FCOM - silently kicks in and gives you 2.5°/sec of nose down trim for 10 seconds - speed increases quickly
  * you may have noticed - amid the cacophony of alarms, perhaps while trying to run an unreliable airspeed checklist - the uncommanded trim movement, but then it stops on its own - so no, this is not a runaway stab trim occurence
  * you pull back on the yoke to avoid overspeeding, and probably trim nose up to alleviate the effort - but not for a full 10 seconds: stab trim is still nose down and speed is not back down to where it started
  * after 10 seconds MCAS is back in action, and gives you another 10 seconds of nose down trim - speed increases further
  * you're now pulling back on the yoke with all your might, but blowback kicks in and despite your best efforts the elevator looses authority

At this point you have just one chance of living through the day by executing this exact sequence of actions:
1) do not heed the backseater pilot deadheading on the jump seat behind you, yelling to cutoff stab trim! At least not yet: if you do, you will not have enough elevator authority to climb out of the dive you're currently in; you need electric trim because hand cranking the manual trim wheel will not be fast enough, and you need both hands to apply as much nose up elevator as you can in the meanwhile
2) use electric trim switch to trim nose up and continue to pull back on the yoke (something they taught you since PPL should not be done: first stick, then trim)
3) if you aren't a smoking hole in the ground by now, get speed under control and back to level flight eventually
4) NOW you must cutoff the stab trim to avoid riding the rollercoaster again

Creepy, and sobering
unquote:
as I am only rated on airbus I cannot comment but this scenario makes a lot of sense to me.
if it happened somehow like this 95% of us superpilots could have been caught in this trap.

It’s not only 3rd world airlines who did not buy the extra AOA displays. I believe United also opted out.