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Training and Safety Tip: Lighten your load

Sometimes called “the poor man’s autopilot,” secondary flight control surfaces commonly known as trim tabs literally take a load off pilots, allowing an airplane to be flown “hands off.”

Photo by Mike Fizer.

However, like many things in aviation, there is a right way—and a wrong way—to adjust trim in flight.

First, a quick primer on trim systems.

Maintaining a given airspeed and altitude requires a happy combination of power and pitch; given that an airplane can be operated over a wide range of both, you have many combinations to choose from. Once established at any given pitch-and-power combination, maintaining that for minutes or hours on end would soon exhaust a pilot who had to constantly exert pressure on the flight controls. The solution is a trim system using trim tabs, balance tabs, servo tabs, antiservo tabs, adjustable stabilizers, or ground-adjustable tabs. The trim tab is most commonly found in training airplanes, but you’ll want to read up on the others for your written and oral exams.

Trim tabs are small, pilot-adjustable “flaps” on control surfaces, designed to catch the relative wind and aerodynamically balance the control in a given position. In other words, once trimmed, the control surface stays put without you having to manually hold it in that position. Your interface for adjusting the trim (most training airplanes only have elevator trim) is a vertical wheel typically located toward the base of the center panel in a training airplane’s cabin and/or an electric switch on the yoke, or, in older airplanes, a charmingly located hand crank on the ceiling.

Properly trimming an airplane allows it to virtually fly itself—at least in calm air. But even in turbulent skies, a properly trimmed airplane is less of a handful to fly and gives you the bandwidth to attend to other flight deck duties.

The right way to trim? First, pitch the airplane to the desired attitude using elbow grease (grandpa-speak for manual labor), then “trim off” excess control pressure. Hold the yoke with your left hand and work the trim control until you are neither pushing against it nor pulling it back. Let go of the yoke and make any final tweaks with small adjustments to the trim wheel.

The wrong way to trim is using the trim wheel like an auxiliary yoke to fly the airplane. Don’t. It’s sloppy, unprofessional, and not what the control was designed for.

In short, set the pitch attitude, then adjust the trim wheel to reduce control pressure.

William E. Dubois
William E. Dubois is a widely published aviation writer and columnist. He is an FAA Safety Team rep and a rare "double" Master Ground Instructor accredited by both NAFI and MICEP. An AOPA member since 1983, he holds a commercial pilot certificate and has a degree in aviation technology. He was recognized as a Distinguished Flight Instructor in the 2021 AOPA Flight Training Experience Awards.
Topics: Flight School, Training and Safety, Student

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