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Training and Safety Tip: Stepping on the ball

Editor's note: This story was updated February 20 to correct an erroneous description of the turn coordinator's function. AOPA regrets the error.

I recall my primary flight instructor reminding me on numerous occasions to “keep the ball centered” on the turn coordinator.

Photo by Mike Fizer.

In my first few flight hours, I found that I could turn the airplane with just the ailerons, so I would forget to also use the rudder pedals to keep the turn coordinated. Most training airplanes are docile, which is why they are good trainers. But once you become a certificated pilot, you may transition to aircraft that aren’t as forgiving as your training aircraft. So, it’s best to establish good habits—such as keeping the ball centered—early on in training.

To appreciate why centering the ball is important, you must first understand what the turn coordinator indicates and what yaw is.

The turn coordinator provides three critical pieces of information: the direction of the turn, the rate of turn, and yaw. Yaw happens when the aircraft rotates around its vertical axis (picture the nose swinging side to side). The other two aircraft axes are lateral (pitch) and longitudinal (roll). Using only ailerons in a turn will roll the aircraft in one direction and simultaneously yaw the aircraft in the opposite direction—unless you use the rudder to counteract this aerodynamic effect known as “adverse yaw.”

The ball within the clear tube at the bottom of the turn coordinator indicates yaw. In a slipping turn, the ball will move to the inside of the turn, and in a skidding turn, it will swing to the outside of the turn. For example, in a slipping right turn, the ball will move to the right of center. To center the ball and coordinate the turn, you “step on the ball” by applying right rudder. Or, when the ball strays to the left, you apply left rudder to center the ball and coordinate the turn.

Keeping your turns coordinated is a safe way to fly. An uncoordinated steep turn or base-to-final turn, for example, could lead to a stall and spin. Short of that, it also makes for an uncomfortable ride for passengers, particularly those seated in the back, farther away from the aircraft's center of rotation.

On your next flight, ask your instructor for a demonstration. At a safe altitude, turn the aircraft with just aileron, then just rudder, then both together. You will notice—and feel—the difference.

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.
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