Trim and Straight Flight?

[Wolf_Rider]

WWII fighter planes are inherently unstable, meaning, evena wind gust/ change will upset the trim.

A Cessna, will for instance, come back to a stable flight after a bit of porpoising, where in the fighter plane, the porpoisoing will get worse.

The idea of trim, is to relieving pilot strain on the stick holding the plane level, which is why (if you look in the cockpit at what the stick does in relation to turning the trim wheel) the stick moves when the wheel is turned.

In a jet for instance trim can be used to set the climb/ descent rate