Anyone know what elevator trim settings are used in the unlimited class as you make your way around the full course? I'd think it would be pretty nose up during the turns probably transitioning to nose down as you roll the wings level toward level. Just curious.
I'm not a race pilots but I do fly aerobatics. You set the trim to a certain value/speed before the sequence starts, and you don't touch it during the sequence. For starters because you don't have enough limbs to do so (one hand on the stick, the other on the throttle) and furthermore because a trim change also changes the characteristics of the aircraft. All of a sudden you are confronted with more or less back or forward stick force for the same maneuver. Not funny. So you simply haul the aircraft around the sky with rudder and stick alone, and don't touch the trim at all.
I would assume air racing is the same. You set the trim, probably for max power horizontal flight, before the race, and leave it there during the race.
What you might be confused with is that people on here are simply talking about a trimtab that apparently got loose. Now I'm not familiar with the P51 trim system but in a lot of aircraft that little tab is not used exclusively for trimming (in the speed stability sense) but also to create artificial stability into the tailplane. The aerodynamics and mechanics are a bit too complicated for now, but without such a tab you're not just lacking speed stability. You also lost all force feedback from the tailplane, which may lead to Pilot-Induced-Oscillations and even flutter. Both of which are not good news.
Even worse would be if the trimtab would detach partly, then bend over and start to act like an aerofoil on its own, forcing the tailplane against the stops all of a sudden. That would induce a massive pitch change.