Salute Vess!
Sounds like the L39 has only a coolie hat switch on top of the stick, heh ?
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I must admit that I only flew one jet that "trimmed" all by itself, and that counts 4 others that went the gauntlet from pure cables, pushrods and pulleys, thru hydrualic assisted control surfaces, irreversible hydraulic systems and then a full FBW system with zero mechanical connections to control surfaces. The auto trim was in the VooDoo, which had a most cosmic A/P. Only trim from HAL was when I selected A/P for attitude control, speed, heading, altitude etc. I also had a A/P coupler that flew the attack scenario and a ILS approach without throttle control. Least I could crash if I didn't pay attention to power, heh heh. But that would be my fault.
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First I saw about auto trim from Hal for the next generation lights was back in the 70's when the Viper FLCS was being discussed in our small community. The non-aero engineer pilots thot the thing had auto-trim. Nope. It trimmed to the commanded gee, and still does 40 years later. We did not have to trim if we slowed down or speeded up. Roll was slightly different due to potemtial rigging of the ailerons and speed could force roll in one direction or the other. This was negligible most of the time because the control law was zero roll rate or whatever you had set.
Even the 'bus is not a pure auto trim, but it's the closest I can find for most flight parameters if auto-throttle is engaged..
I would like to see an official flow chart from Boeing that shows the interaction of STS and MCAS. Inputs and outputs to the stab and cockpit displays when things were awry.
Gums sends...