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When You Should Use Trim

When should you trim as you fly? It's a question we get asked all the time. Here's what you need to know...

What Does Trim Do?

Trim holds airspeed. If you trim for a speed and let go of the yoke, your plane will keep flying at that speed, regardless of power setting. If you trim and change your power, your plane will pitch up or down to maintain your trimmed speed. Trim for climb speed, let go, and you'll maintain climb speed. Trim for cruise, let go, and it'll maintain cruise speed. Trim for final approach speed, let go, and you'll maintain final approach speed. The list goes on. Trim holds airspeed.

That's how trim works in a perfect world. In reality, you might have to continue making small power, pitch, and trim adjustments to maintain attitude and speed. Click here to learn everything you need to know about how the 4 different types of trim tabs work.

_ Night Flier _

When To Use Trim

Pilots debate all the time about when trim use is or isn't appropriate. Simply put, there's no right answer, and the choice comes down to personal preference. Each flight instructor teaches their students a little differently, often by the strategy they personally use. Let's dive into when trim should be used, and what you should be aware of as the pilot flying.

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Straight And Level

Your workload in cruise flight is greatly reduced when the airplane naturally wants to fly straight and level. If your goal is straight and level flight, you should only need to make a few small adjustments to elevator to find the sweet spot.

Hold the controls lightly as you trim the airplane up or down. Keep your eyes outside the cockpit and note changes in pitch. Continue making tiny trim changes to find the spot where little to no forward or back pressure is required from your hands on the yoke. When you're perfectly trimmed, you should be able to take your hand off the yoke and continue flying without pitching up or down.

Trim requirements can change fairly dramatically in cruise at different speeds and power settings. As you add power, you'll notice that the nose tends to pitch up. But why? The airplane pitches up for two main reasons.

  • First: There's increased air flow over the horizontal stabilizer and elevator. Adding power and increasing airspeed will result in increased tail down force, causing the nose to rise. The opposite is true of when you reduce power.
  • Second: The location of the center of thrust is below the center of gravity in most GA aircraft, creating an upward pitching moment with increased power. This is true for most airplanes, but not those with a center of thrust above the center of gravity.

Because of this, a constant trim setting will only hold you straight and level at a constant airspeed and power setting.

Climbs And Descents

Just like straight and level flight, small adjustments to trim should be used during climbs and descents to maintain a desired airspeed. On climb (or descent), pitch for your airspeed. Then, hold the controls lightly as you trim the airplane up or down. Continue making small trim changes to find the spot where little to no forward or back pressure is required on the yoke. That'll make your climbs, as well as your descents a lot easier! Keep in mind, if you need to pitch for a different airspeed during climb or descent, you'll need to re-trim the airplane.

Steep Turns

Should you use trim during a steep turn? This is where the real debate starts. The point of a steep turn is to develop simultaneous bank, power, coordination, back pressure, rollout, and trim skills. Hand-eye coordination is improved as steep turns are perfected.

Some pilots prefer to leave their level flight trim alone as they enter a steep turn, and instead just use back pressure on the yoke or stick to maintain altitude. Pilots who don't use trim often like the feeling of holding constant back pressure, for one big reason. The heavier control forces required make it more difficult to over-control the airplane inside the turn, so it gives the sense of more stable flight. On rollout, pilots using this technique don't need to re-trim the airplane very much. This doesn't work for everyone, however.

Many pilots feel like they're able to control the airplane better when it's trimmed in a turn for the exact opposite reason, because less back pressure is required. Upon entering a steep turn, one or two downward flicks of the trim wheel (nose-up) is all you need. Less back pressure means that pilots who trim the airplane are able to relax their muscles and better focus on other aspects of coordination. In some cases, the pilot simply might not have the arm strength to comfortably maintain strong back pressure throughout the turn. There's nothing wrong with that.

If you do trim, be aware that on rollout you'll have to re-trim the airplane and apply forward pressure, or else risk climbing right away. Since all of your lift will return to acting vertically, a few upward flicks of the trim wheel (nose-down) is all you'll need to help.

So is it wrong to use trim in a steep turn? Nope. It's just a matter of personal preference. Either way you go, flight loads will change on rollout and you'll have to adjust back pressure, trim, or both. This is one reason why steep turns are so valuable; they help pilots develop good trim habits that work for them.

Better yet, the same skills apply to the traffic pattern. The basic skills your learned from steep turns should be used for many of your shallow turns, including those in the traffic pattern. As you make turns in the traffic pattern, you'll need to either add back pressure or nose-up trim to prevent your airplane from trending nose-low.

Final Approach

Another point of contention is how much trim to use on final approach.

If you haven't done them before, ask your instructor to demonstrate elevator trim stalls. They're stalls caused by adding full power when flying with substantial nose-up trim, without proper forward pressure on the controls to prevent a high pitch attitude as full power is added.

Imagine flying a perfectly trimmed, hands-off approach to the runway. Elevator trim stalls are supposed to replicate what would happen during a go-around with this kind of trim setting and not enough forward pressure on the yoke.

Because of the risk for an elevator trim stall, some instructors don't recommend trimming at all on final approach. But does this make sense? Just because the nose will pitch straight up during an elevator trim stall, doesn't mean we shouldn't use trim on final approach. It just means you need to apply forward control pressure and begin rolling trim forward on go-arounds as soon as practical. Having a little bit of nose-up trim on final approach is a great way to ensure you're able to roundout and flare without your nose touching down before the main wheels.

Once again, trim preferences divide sharply at this point, and there's no definable "correct" way to do it. Like steep turns, some points prefer flying final approach with heavier control pressures, while some don't.

But for most pilots, trimming on final is a what you should do. Trim will help you fly more stabilized, on-speed approaches. And doing that almost always results in better landings.

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Don't Trim Incorrectly

Trim is important, and you really should use it to reduce your workload. But you should not fly the airplane using trim alone. Some pilots have a tendency to use trim, especially electric trim, to initiate climbs and descents. Avoid this...don't use trim to point the nose where you want it to go. Instead, think of trim as tape. First, use your hands on the controls to set the airplane in place, then add trim (or tape) where you want it to stick, and let go.

GolfCharlie232

Easy enough, right? There's no "perfect way" to trim an airplane. Using trim is an awesome way to reduce your workload in the cockpit, so you can divide more attention away from just keeping the airplane level. Practice trimming during every phase of flight, as well as maneuvers like steep turns, and see what works for you.

How do you use trim? Tell us in the comments below.

Swayne Martin

Swayne is an editor at Boldmethod, commercially licensed pilot with multi-engine and instrument ratings, and a commercial aviation student at the University of North Dakota. He's the author of the articles, quizzes and lists you love to read every week. Swayne's experience ranges from international flights in a King Air F90 to ferrying a 1943 Grumman Widgeon across the country. You can reach Swayne at swayne@boldmethod.com, and follow his flying adventures at http://www.swaynemartin.com.

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