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Training and Safety Tip: Just a little trim

Using the trim wheel doesn't come naturally to some new pilots. However, once it becomes part of their routine, they may wonder how they ever flew without it. Let's break down the mystery of this essential tool.

Photo by Mike Fizer.

The wheel (in some airplanes it's a crank) inside the cockpit has a "take-off" indication; setting the trim to that position is part of the pretakeoff checklist. From that point, the wheel can be rotated one way for "nose up" and the opposite way for "nose down" trim. Doing so relieves the pressure on the yoke in the corresponding direction, making the airplane easier to control and reducing the pilot's workload. The location of the trim wheel and its sensitivity vary from one airplane to another, so it will take practice to determine how much trim is needed.

Trimming should be done anytime there is a change in the pitch of the airplane. For example, when climbing, descending, or leveling off, trim should be applied, heeding the old adage, "pitch, power, trim." For new pilots, it's a learned behavior, but, done correctly and regularly, it becomes a habit. To verify the trim is being used correctly, briefly take your hands off the yoke. If doing so results in the airplane doing anything but maintaining the intended flight attitude, trim is not being used correctly. Once you adjust the trim, the airplane will maintain attitude or remain steady during climbs and descents.

There are several types of trim systems. For many general aviation aircraft, the trim tab runs along the trailing edge of the elevator. When the pilot moves the trim wheel in the nose-down direction, the trim tab moves up. As described on Page 6-10 of the Pilot’s Handbook of Aeronautical Knowledge, "With the trim tab up and into the airstream, the airflow over the horizontal tail surface tends to force the trailing edge of the elevator down." When that happens, the tail moves up and the nose goes down. And, vice versa, when the trim wheel is moved in the nose-up direction.

Trimming the aircraft is a critical flight control function and is a sign of good piloting skills. Incorporating the trim wheel into all phases of flight in every flight enhances control, and the resulting smoothness and precision surely contribute to safety and enjoyment.

ASI Staff

Kathleen Vasconcelos

Kathleen Vasconcelos is an instrument-rated flight instructor and a commercial pilot with multiengine and instrument ratings. She lives in New Hampshire.
Topics: Training and Safety, Student, Technique
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