Pilots use the rudder to maintain coordination throughout the phases of flight, unless there is a specific situation in which you don’t want to be coordinated (e.g. landing in a crosswind or slipping to increase drag on approach).
There are a variety of turning tendencies and aerodynamic forces on our aircraft, and the magnitude of each is always changing depending on power, angle of attack, bank and airspeed. Even an airplane climbing at a constant airspeed and AOA with wings level will still experience changing aerodynamic forces as power decreases with decreased air density. In certain phases of flight, like takeoff and low-speed turns, these changing forces can necessitate large rudder corrections to maintain coordination. You may consider reviewing lessons on adverse yaw and turning tendencies.
Hence, it is the pilot’s task to ensure that the airplane is coordinated at all times.
Keep the Wings Level: Many pilots often think of rudder coordination as something only required in turns; but the most fundamental step in coordinating is to learn to use enough rudder pressure to keep the airplane straight in level flight. Generally speaking, if you can take your hands off the yoke and the airplane doesn’t turn one direction or another, you are coordinated. Make it a goal to see how long you can fly like this.
With practice, you will learn to make rudder adjustments every time you make a change: turning, power settings, change in angle of attack, etc. The same rules still applies: keep the wings level. But what about when you turn?
In a turn we determine coordination by watching the nose of the airplane, or, more accurately the entire longitudinal axis of the airplane. If we turn and make no attempts to coordinate the turn, the nose will swing to the outside of the turn: a result of adverse yaw. You will feel yourself move sideways in the cockpit, and it’s generally not comfortable, particularly for passengers.
Look outside, add aileron and rudder simultaneously. Adjust rudder input as required to keep the nose pivoting. Then mostly neutralize the controls through the turn. Then do it in reverse to roll out.
Instead, we should see the nose/longitudinal axis of the airplane smoothly rotate about the horizon until our bank is established. This takes some, well, coordination. But use enough rudder to make the airplane rotate about the axis, like a hotdog over a campfire, rather than like a ship sloshing in a rough sea.
Why is rudder coordination important?
Why must pilot continuously vary rudder pressure?
How do we measure whether we are coordinated in straight (wings level) flight?
How do we determine coordination in a turn?