A student pilot is leveling off a Cessna 172 in cruise for the first of a three-leg, 150-nautical-mile solo cross-country. She lowers the nose, patiently lets the aircraft accelerate before reducing power to the desired cruise setting, then nudges the trim wheel forward until she no longer must hold forward pressure on the yoke to maintain the pitch attitude.
The air is smooth so it should now be possible to fly hands-off until making a course or altitude change, and with this workload-reducing task accomplished, she turns next to navigating and communicating with air traffic control to request radar flight following.
All that was before she learned that you can’t trim until you have succeeded in establishing the aircraft in the condition you want to trim it for—which required patience. She also came to realize that certain disturbances, such as light turbulence, don’t require you to react to every minor pitch upset with pitch and trim inputs. You can let the airplane fly because it will restabilize.
Another time-tested tidbit about trim technique was discovering that once the airplane was pitch-trimmed, it would maintain its trimmed airspeed after power was reduced for the descent to the destination airport unless the pilot chose to change airspeed with a pitch adjustment, or reconfigure with flaps.
Experience also taught that one trim scenario requires caution: a go-around.
When full power is applied to go around, an airplane on short final, power-off at, let’s say 55 knots, may pitch up aggressively as it transitions from idled throttle to takeoff power.
In this high-workload scenario, immediately “rough-trimming” to overcome the strong pitch-up response helps the pilot avoid an excessively nose-high attitude. Once the aircraft is safely climbing, it’s time to “fine-trim” and relieve any remaining yoke pressure during the climb at the recommended airspeed.