How's your turn?

Rather than build a flying machine that rode the waves like a ship, solid and imperturbable, the brothers worked on making the aircraft steerable, so its pilot could bring it about and cope with changes in the air. One of early aviation’s greatest achievements was Wilbur Wright’s completion of the first circular flight on September 20, 1904.

As one of the four fundamental modes of flight—along with straight-and-level, climbs, and glides—turns are often given short shift after being introduced in the first hour of flying lessons. And yet, as a part of the foundation of everything we do with an airplane, they deserve more study and diligent practice. I tell every student to make every turn as perfectly as they can, so they’ll get better and better, until a good turn becomes second nature. Sloppy turns result from inattention to small details, a basic flaw that transfers to other maneuvers.

For instance, do you finish a turn 50 feet higher than when you began? Or do you pay attention to altitude deviations at all? Do you roll out 10 degrees past your intended heading, then wobble your way back to it? Does your bank angle wander as the airplane comes about, and does the slip ball habitually ride partway out of its cage? These aren’t big items, but they distract us from what could be perfection. Lest I be accused of being engaged in over-obsession, I realize there are times when we have better things to do than correct minor blemishes in a medium-bank turn. But if we don’t work on improvement as time permits, we’re doomed to accept second-rate performance.

How does it work?

The details of what makes an airplane turn can be confusing (see “What Makes an Airplane Turn?” below), but if I bank the wings, something called the horizontal component of lift will push the airplane around in a circle. No bank, no turn; more bank, more turn—that’s the way it works. Oh, I know it’s possible to perform a flat turn by holding aileron against firmly applied rudder, thereby skidding our way through a curved path. As a practical matter, though, airplanes and passengers much prefer coordinated flight, with bank as the primary ingredient and rudder used to maintain coordinated flight.

The act of rolling into a bank requires a bit of persuasion, because the airplane is designed to maintain straight flight. Its tail acts like the feather of an arrow, resisting minor disturbances, and the displacement of the ailerons at the wing tips creates a yaw input that’s opposite to the desired direction of the turn, called adverse yaw. Modern aileron designs and slow control movements may allow us to ignore compensating for this resistance, if we choose to do that, but the turn’s entry—and subsequent recovery—will be a sloppy procedure.

It’s far better to tap some rudder pedal as the turn begins, along with aileron, which brings in a little pre-turn yaw to offset the adverse yaw of aileron movement and breaks the airplane out of its insistence on straight flight. Airplanes of many years ago needed lots of rudder to initiate turns. In our case, modern differential ailerons only require a little coordinated rudder to produce a smooth roll-in and rollout. We have but to watch the slip ball to get a grade; it should remain essentially unmoved as we go in and out of turns. Passengers will likewise remain undisturbed in their seats.

In level flight, our wings primarily produce vertical lift. Once the turn is underway that lift vector changes, and we produce both vertical and horizontal lift. Because we are now making less than the necessary amount of vertical lift to overcome our weight, our altitude will begin to drop unless we add a little more, obtained only by increasing angle of attack by pulling back on the stick or yoke or speeding up. Thus, every turn entry and recovery require the use of three controls: ailerons, rudder, and elevator. Unlike an automobile, the wheel or stick is returned to neutral after the turn is begun, along with the rudder pedals; only the elevator pressure is maintained throughout. The elevator is “lifting” the airplane around the turn.

It is important to hold a steady bank angle during the turn if you want to maintain a constant altitude or, in the case of climbing and gliding turns, the correct airspeed. Allowing the bank angle to shallow produces a climb and letting it steepen tends to create a descent, in the absence of changing elevator pressure. If you want the turn to remain level, keep the bank immobile.

Turns, great and small

The typical bank angle chosen for “medium turns” is about 30 degrees, mild enough to avoid challenges to skill but effective enough to bring the airplane around quickly. Once medium-bank turns are mastered, we will proceed to steeper turns as a skill-building maneuver. At 45 degrees of bank, the pilot is required to add considerable up-elevator to keep altitude steady, nudging in a bit of throttle to keep a fixed-pitch propeller’s rpm from dragging down and airspeed from deteriorating. Steep turns begin to manifest an overbanking tendency; rather than holding at a stable bank angle, the bank would really like to increase itself. A small increment of “outside” aileron pressure may be required to keep the bank steady.

Don’t fixate on the panel’s attitude indicator for a perfect turn. Instead, use the natural attitude indication of the horizon in the windshield. Learn where the nose of the aircraft is pointed in relation to the horizon during a left or right turn and keep it fixed in that attitude. Use the altitude and bank indications only as confirmation that your basic outside references are correct. After all, outside is where the other airplanes are, which is why you’re clearing the airspace you’re going to occupy before you begin a turn. Even while practicing, have your eyes outside 80 percent of the time.

Instrument pilots, brooding introverts that they are, avoid trouble in the clouds by doing only “standard rate” turns that move the heading at a sedate 3 degrees per second. Most training airplanes achieve this rate of turn at about 15 degrees of bank; faster airplanes will need 20 or 25 degrees of bank. But we generally limit instrument turns to 30-degree maximum bank angles, regardless of speed. VFR pilots will use these benign bank turns during climbs, to allow most of the engine’s power to go into producing climb, and in slow flight turns, where there’s a stall lurking a few knots away.

As a general rule, coordinated level turns in slow flight can be made at bank angles up to 30 degrees without worry about the stall speed increase from added G-load. If you inadvertently let the bank get too steep at slow speed, just drop the nose and unload the wing while rolling out. Trading a little altitude for speed is better than stalling during the turn.

Gliding turns, like climbing turns, require attention to airspeed control, rather than maintaining altitude. To hold a steady best-glide speed, back-pressure is added to the elevator control after the turn is begun, proportionate to the amount of bank used, and released as you roll out of the turn.

Rolling out of the turn requires a little anticipation as the heading indicator moves through the numbers. We don’t want to snap the passengers’ necks by instantly banging into straight flight, so let’s begin the rollout about 5 degrees prior to our chosen heading, remembering to squeeze in a little rudder with the aileron. Be careful, now that you know what the rudder is for; your legs are at least twice as powerful as your arms, so use small displacements. Don’t forget to release the back-pressure you’re holding as the wings become level, lest the airplane jump 25 feet during the rollout.

Make every turn the best you ever did. It won’t take long to see them become smoother and more precise without even trying. Your future passengers may not ever notice, but you will.

LeRoy Cook is an airline transport pilot, instructor, and frequent contributor to AOPA publications.

What Makes an Airplane Turn?

By Dave Hirschman

The practice checkride begins with a deceptively simple question.

“What makes an airplane turn?” the examiner asks.

Seated in front of a wooden desk in the examiner’s windowless airport office, the CFI applicant tries to lighten the mood with a few quips.

“Well, if money makes an airplane fly, then I suppose a little more or a little less of it could make it turn,” he offers.

The examiner impassively awaits a real answer. An uncomfortable silence ensues as the applicant starts to squirm. Then he asks a few questions of his own. What phase of flight is the airplane in? What’s its configuration.

The pokerfaced examiner replies the airplane is straight and level in cruise, and it’s not accelerating or decelerating.

The applicant takes a deep breath and launches into an explanation of how he’d teach a student to turn: “Use the yoke and rudder together to start a bank, and then…”

The examiner cuts him off.

“That’s not what I’m asking,” he says. “Treat me like a primary flight student and explain what causes an airplane to move from straight and level unaccelerated flight to a coordinated turn. What must the control surfaces do to make that happen?” He points to the airplane model on his desk, a plastic Cessna 172 with moveable control surfaces.

The applicant tries another approach.

“OK, turning the yoke moves the ailerons,” he says. “One goes up, and the other goes down, and the airplane banks in the direction of the upturned aileron.”

The examiner nods approvingly.

“So, you’re telling me that ailerons cause the airplane to turn. Is that it?”

The applicant senses a trap and hedges.

“Well, that’s part of it.”

The examiner asks for a clarification. “Before you tell me the rest, I’ve got a question about what you just said about ailerons. Why does the airplane bank in the direction of the upturned aileron?”

“Oh, that’s easy,” the applicant says confidently. “The wing with the upturned aileron provides less lift than the wing with the downturned aileron—so that difference in lift makes the airplane roll in the direction of the wing with the upturned aileron.”

The examiner, still playing the part of a student, acts perplexed.

“OK, the difference in lift between the two wings makes sense to me so I can understand why the airplane rolls toward the wing that’s making less lift,” the examiner says. “But the wing that makes more lift also makes more drag, doesn’t it? So why doesn’t the airplane turn in the direction of the wing that’s making more drag?”

The applicant has a ready answer.

“That’s the other part of what I was going to tell you,” he says. “It’s the rudder. When you roll into the turn, you add rudder in the direction of turn. That counters adverse yaw—the thing you mentioned about the airplane’s tendency to yaw in the direction of the wing with the downturned aileron.”

The examiner nods again.

“OK, now I feel like I’m making progress,” he says. “So you’re telling me that ailerons and rudder together make the airplane turn. Is that right?”

The applicant nods warily.

“That’s pretty much it,” he says.

The examiner’s face takes on a troubled look again.

“I’m still not sure I get it,” the examiner sighs. “You told me about ailerons and rudder, and I understand how they can cause an airplane to roll left and right. And I think I understand what you’re saying about the rudder countering adverse yaw. But that still doesn’t explain what makes the airplane turn. Is there something more to it? What am I missing?”

The applicant responds with a word salad of aeronautical terms. Angle of attack. Lift vector. Angle of incidence. Wing loading.

This verbal smoke screen continues until the examiner cuts through it with another question.

“Here’s the thing I keep coming back to,” the examiner says, “What’s happening with the elevator during this whole process? Does the elevator play any part in the turn you’re describing?”

“Well, the steeper you bank, the more back-pressure you must apply to keep the airplane’s nose from dropping,” the applicant says.

The examiner arches his eyebrows and provides another hint.

“Well, it seems like what you’re telling me is that as the airplane’s bank angle gets steeper, and the pilot adds more back-pressure, that increases the horizontal component of lift and causes the airplane to turn. So what you’re saying is that it’s actually the elevator that makes the airplane turn.”

The applicant smiles and accepts the gift.

“That’s exactly the point I was trying to get across to you,” he says. “It’s the elevator that makes the airplane turn.”