trim_tab

Photo courtesy FS-Force

As a kid, telling your mom you planned to try something without holding on was a tipoff that something dangerous was surely in the offing.

But when I tell flying students to try letting go of the control wheel or stick at times when I first get to know them, I’m actually trying to help them become better pilots. In my case, it’s all about learning to trim the airplane. Pilots who fail to learn the purpose of the trim tab – that little piece of hinged metal on the end of the elevator – or the movable horizontal stabilizer really are doomed to work way too hard at becoming truly good pilots. I often find though that many instructors don’t take enough time to explain the “why” behind trimming an airplane.

Most simply put, trim tabs help maintain an airplane’s state of balance where all four of those basic forces we learned about as student pilots — power, lift, drag and gravity — come together. Alter any of the forces and you’ll need to re-trim the aircraft to reestablish that balance.

Failure to reestablish balance and the pilot’s forced to hold back or forward pressure on the control wheel to maintain altitude or airspeed. That might not seem like a big deal, but it’s just one more brain function that’s not available for other important things like navigating, looking out the window for other airplanes or drones, or keeping an eye on the weather.

The Nuts and Bolts

Here’s how you can make your flying life a little easier. Next time you’re out solo in level flight, simply let go of the control wheel or stick and watch what happens to the nose of the airplane. If the airplane’s properly trimmed, you won’t notice any change at all.

But if the airplane’s nose drops and the airspeed begins increasing, you’ve been holding the nose up. An opposite reaction means you’ve been holding it down. Again, that means you’re working too hard.

So how do you fix the problem? The worst thing you can do right now while you’re not grasping the control wheel is to begin fussing with the trim wheel. Trying to fix a balance problem by only trimming and you’ll end up chasing the nose in an endless series of up and down pitch changes. This happens quite a bit when the aircraft is equipped with an electric trim button on the control wheel, because that seems like the quick solution.

The trick though, is to grasp the control wheel and set the nose pitch where you want it first. THEN trim until you feel no pressure at all. If you’ve done it right, the pitch won’t change when you release the wheel. Still not quite right? Grasp the wheel again and trim just a teensy weensy bit at a time and let go again.

Want to hold 85 knots in level flight? Set the power and pitch for that speed and trim just a bit nose up or nose down and let go. If you did it all correctly, that airplane will cruise just dandy at 85 knots until one of the forces changes. Same works to set up a descent. Set the power, drop the flaps and trim until the airplane holds the speed without any pressure on the wheel from you. There shouldn’t be any configuration on any airplane that won’t allow you to trim off the pressure you’re holding unless something is wrong somewhere. Climb at 85 and trim off the pressure. It even works in a steep turn if you’re ready for it … turn and trim.

One final tip. If you haven’t yet earned an instrument rating yet, trust me … learning to properly trim the airplane will make your training a whole lot easier. Creating good instrument flying skills will at times seem to require every ounce of brain power your have. Now you’ll know how to tweak just a bit more from that gray matter when you just might need it.

Fly safe.