The chief pilot of an aviation company I once worked for was like a human yaw detector: If you allowed even the slightest bit of slip or skid into your aircraft-control technique when he was aboard, he would emit a groan easily audible above the roar of the engine or engines.
No yawing motion could slip by him, and the echoes of those old groans still pay dividends because the pilots he and his instructors trained learned quickly to feel the difference between coordinated flight (smooth) and uncoordinated flight (it feels like you are being shoved sideways in your seat).
Their confidence is justified because it is uncoordinated flight that feels uncomfortable enough to bring on that queasy feeling, or in a worst-case scenario, turn a stall into a spin.
It stands to reason then, that correct use of rudder during turns, climbs, and descents keeps the ball of the inclinometer—the component of a turn coordinator that displays slipping or skidding—motionless in the middle of its curved, sealed tube. And given turn coordinators’ placement on most “steam-gauge” instrument panels as a second-tier instrument or tucked away in a corner, the pilot’s ability to sense uncoordinated flight without having to look down at a gauge to “step on the ball” is a major plus that keeps the eyes focused outside for scanning for traffic and navigating.
How can you develop that “feel” for coordinated flight? A good start is a well-known warm-up exercise for your flight lessons: While cruising to the practice area, position a prominent landmark (like a mountain peak) at 12 o’clock, and gently roll your wings back and forth using a shallow bank. Use rudder pressures to keep the nose fixed on your reference point. Don’t be shy about pressing the pedals; the goal is to prevent the drag produced by the ailerons as you bank the aircraft from pulling the nose off your reference point.
To fully appreciate the concept, try the exercise briefly without rudder; note how the nose swings opposite the direction you are banking, and how the yawing sensation feels like someone is pushing you out of your seat—possibly enough to make you groan.