[Freelansir]

Regarding trim, I found the best first-person description from Bud Anderson's story "He was only trying to kill me".

A lot of this is just instinct now. Things are happening too fast to think everything out. You steer with your right hand and feet. The right hand also triggers the guns. With your left, you work the throttle, and keep the airplane in trim, which is easier to do than describe.

Any airplane with a single propeller produces torque. The more horsepower you have, the more the prop will pull you off to one side. The Mustangs I flew used a 12-cylinder Packard Merlin engine that displaced 1,649 cubic inches. That is 10 times the size of the engine that powers an Indy car. It developed power enough that you never applied full power sitting still on the ground because it would pull the plane's tail up off the runway and the propeller would chew up the concrete. With so much power, you were continually making minor adjustments on the controls to keep the Mustang and its wing-mounted guns pointed straight.

There were three little palm-sized wheels you had to keep fiddling with. They trimmed you up for hands-off level flight. One was for the little trim tab on the tail's rudder, the vertical slab which moves the plane left or right. Another adjusted the tab on the tail's horizontal elevators that raise or lower the nose and help reduce the force you had to apply for hard turning. The third was for aileron trim, to keep your wings level, although you didn't have to fuss much with that one. Your left hand was down there a lot if you were changing speeds, as in combat . . . while at the same time you were making minor adjustments with your feet on the rudder pedals and your hand on the stick. At first it was awkward. But, with experience, it was something you did without thinking, like driving a car and twirling the radio dial.

It's a little unnerving to think about how many things you have to deal with all at once to fly combat.