Many private pilots who were trained in airplanes using manual trim wheels, cranks or knobs have transitioned to aircraft equipped with electric trim without being trained to recognize a runaway trim condition. A malfunctioning trim control switch, relay or other electrical component can cause the trim motor to run out of control, ultimately moving the trim surfaces to dangerous positions. In the blink of an eye, you can find your aircraft lurching out of its smooth cruise configuration into a dive or a stall.
Recurrent training is a good way to emphasize the importance of proper rudder, aileron (when available) and pitch trim settings. You can practice flying with improperly set trim tabs and watch the airplane slipping, skidding or otherwise performing badly. During takeoff, without the trim in the proper position, you’re going to have difficulty rotating and climbing. The control inputs to maintain heading and reasonable climb attitude will seem strange. If you’re in a twin, you might think an engine is in the process of going belly up. And if you’ve punched into instrument conditions with a serious trim anomaly, you’re really going to have your hands full. Landing an improperly trimmed airplane also can be a daunting task since it’s hard to maintain precise control of the airspeed and heading when you’re being called upon to apply brute force to the control surfaces.