When it comes to these kinds of discussions, folks often look for the "bottom line" and end up disappointed because it seems that one isn't reached.
The chief culprit here is that in aviation there are few absolutes, and the subject of trim is an excellent example. As Toad mentioned, there were many, many aircraft designs in WW2, spanning a wide range of technology. Trying to find a "one size fits all" answer is not easy. These planes had various trim designs ranging from the non-existent to the complex. Not all aircraft were designed perfectly...aerodynamic oddities did exist and sometimes defied conventional practice.
For us, we have the additional problem of separating the sim world from the real. As has been explained, trim is a function that is difficult to reproduce in a sim. The developers, when producing a multi-plane sim, find that programming each different aircraft like its real life counterpart is far too impractical. So we end up with planes that have a trim function in the sim that they did not have in RL. We can live with this!
We have been tossing around the idea of trim "improving turn performance". I think the real issue is separating the terms that we are really talking about...chiefly "turn performance" and "stick authority".
When we talk "turn performance", we are referring to turn rate and radius. These two are affected by true airspeed and radial G...nothing else....more G at less speed equals more degrees per second and a smaller turn radius.
"Stick authority", on the other hand, is a reference to the control surface movement that a pilot can obtain in flight. Here is where we may get confused when looking at the trim issue. At high speeds, the air loads on the control surfaces make the controls harder to move...it simply takes more force to move the stick. And at these speeds, the performance values are excessive (large radius, low rate). If the pilot cannot get full travel on the stick because of air loads, he may be unable to get the maximum performance available. IF his trim function can independently operate the control surface to produce an increased range of movement, then the pilot may see some performance improvement. There are limits to how far this technique can be taken...these are the design G limit of the plane and the ability of the pilot to maintain consciousness under high G loads.
As a rule, when trim was used to improve stick authority, it was in situations such as a high speed dive recovery. It was not widely used to improve turn performance numbers...not that the technique couldn't be used in some cases...it just wasn't the norm.
Generally speaking, pilots entered the fight trimmed for the speed at the merge, and they tended to leave the trim at that position during maneuvering. The exception to this was when the maneuvering took the pilot to the boundaries of the flight envelope (slow or fast). There, he may have trimmed to either relieve stick loads or to gain stick authority as previously described.
When the fight stayed in the middle of the speed range, as was the norm, then there was little reason for trimming. Air loads were not a factor, and the pilot had far more problems to be worried about than a stick that was slightly "heavy". Trimming was done by exception. At these speeds, the pilot could reach full stick authority...because of this, actuation of the trim function would not confer any advantage...it only reduced stick forces.
Now, that's RL. If the sim is programmed differently, then all of this is moot. If the pilot can add elevator trim when in the "normal" speed range and realize an increase in turn rate or decrease in turn radius, then the sim has provided him an advantage the RL pilot did not have. I'll leave it up to the folks that know more about how our sims are programmed to figure this issue out. If the trim can provide a performance advantage, then this should be announced from the gitgo in the sim's documentation. We don't want some folks to have an unfair advantage because they are in the "know" and others aren't!
Andy
