Umm.....actually, they do work aerodynamically! Trim tabs are initally set by the manufacturer to make the blade fly the same as the master in their whirl tower. When the blade is installed track adjustments will be made using the pitch change rods. However all things not being equal due to age and wear etc.., some blades will change there track position with increase in airspeed. To compensate for this the trim tabs are then adjusted.
