Anno v. Heimburg writes:

Okay, now that I've made the mistake of reading this discussion, you've got
me curious: How does your plane's trim work? It's obviously not a trim tab.
And how can there be no neutral/default position of the elevator or the
trim device?

The neutral position of a trim tab is the position in which it does
not intefere with the flow of air over the control surface, and thus
does not deflect the control surface in either direction.

There is no default position of a trim tab, as it is set as
appropriate for circumstances, which vary widely. In my use of the
term, I was thinking of trim positions that compensate for specific
power and pitch configurations and the like, excluding those that
compensate solely for a poorly balanced payload or fuel load.

In other words, I make a distinction between trim used to maintain the
aircraft in a specific, normal flight configuration, and trim used to
keep the nose from pitching violently upward because there's so much
junk loaded in the back of the aircraft (or violently forward because
the pilot and copilot are heavy and there's no ballast behind them).

As I understand it, the manufacturer's CG envelope is designed to
ensure adequate remaining control authority for any CG within the
envelope. I'm not sure how they determine what is adequate, however,
so I still worry. Which is why I'd like the most neutral CG possible,
that is, the one that has the least tendency to induce pitch or roll
movements.

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