Airplane Level Turns

A level turn is a flight maneuver in which an airplane changes heading while maintaining a constant altitude. To perform a level turn, the pilot must coordinate the ailerons, elevator, rudder, and power to establish the desired bank angle, maintain altitude and airspeed, and return to straight-and-level flight on the desired heading. Understanding the relationship between bank angle, lift, coordination, and turn radius is essential for performing safe and accurate turns.

A turn is initiated by banking the wings in the desired direction using the aileron flight controls. Left aileron input lowers the left wing, while right aileron input lowers the right wing. In other words, to turn left, the pilot lowers the left wing; to turn right, the pilot lowers the right wing. Depending on the airplane’s design, stability characteristics, airspeed, and bank angle, the airplane may tend to maintain or increase its bank after the ailerons are neutralized.

The basic sequence for establishing a turn is as follows:

1. Bank the airplane in the desired direction using coordinated aileron and rudder inputs. Apply appropriate elevator back pressure and adjust power as necessary to maintain altitude and airspeed.
2. Adjust the aileron and rudder pressures as necessary to establish and maintain the desired bank angle.
3. Apply coordinated opposite aileron and rudder pressure to reduce the bank angle when preparing to roll out of the turn.
4. As the wings return to level, adjust elevator pressure and power as necessary to resume straight-and-level flight. [Figure 1]

A turn involves the following controls and aerodynamic principles:

• Ailerons: The ailerons bank the wings. For a given airspeed, the bank angle largely determines the rate of turn. Banking divides the lift force into vertical and horizontal components. The horizontal component curves the airplane’s flightpath toward the turn.
• Elevator: The elevator changes the airplane’s pitch attitude. During a level turn, the pilot generally needs to increase elevator back pressure to increase the angle of attack and maintain sufficient lift to support the airplane’s weight.
• Vertical fin: The vertical fin contributes to directional stability and helps the airplane maintain directional alignment. It is not the primary source of the horizontal force that turns the airplane.
• Throttle: The throttle controls engine power and can be used to help maintain airspeed during a turn. Additional power may be needed to compensate for increased drag, particularly in steeper turns.
• Rudder: The rudder helps maintain coordinated flight by correcting adverse yaw caused by aileron deflection and other yawing tendencies associated with the airplane’s design and powerplant. The rudder is not the primary control used to turn the airplane.

For instructional purposes, turns are divided into three classes: shallow, medium, and steep.

• Shallow turns: These generally involve a bank angle of approximately 20° or less. In many airplanes, lateral stability tends to return the wings toward level flight unless the pilot maintains some aileron pressure in the direction of the turn.
• Medium turns: These generally involve bank angles between approximately 20° and 45°. Depending on the airplane’s stability characteristics, the airplane may tend to maintain a relatively constant bank angle after the initial bank is established. The pilot adjusts the control pressures as necessary to maintain the desired bank.
• Steep turns: These generally involve a bank angle of approximately 45° or more. The airplane may have an overbanking tendency, requiring opposite aileron pressure to prevent the bank angle from increasing. The amount of corrective pressure depends on the airplane, airspeed, and bank angle.

When an airplane is flying straight and level, lift acts perpendicular to the wings and has a vertical component that balances the airplane’s weight. As the airplane banks into a turn, the lift force is inclined relative to the Earth and can be resolved into two components: vertical and horizontal. [Figure 2]

The vertical component of lift supports the airplane’s weight, while the horizontal component provides the centripetal force needed to curve the airplane’s flightpath. These components act at right angles to one another, and their resultant is the total lift force acting perpendicular to the airplane’s wings. The horizontal component of lift, rather than the rudder, is primarily responsible for turning the airplane.

During a turn at constant altitude and airspeed, the pilot generally needs to increase the wing’s angle of attack by applying additional elevator back pressure. Power may also need to be increased to compensate for the additional drag. These adjustments are necessary because the vertical component of lift decreases as the airplane banks. Total lift must increase sufficiently to maintain the vertical component required to support the airplane’s weight.

The purpose of the rudder during a turn is to maintain coordination. When the pilot deflects the ailerons to bank the airplane, the rising wing generally develops increased lift and drag, while the lowering wing develops decreased lift and drag. [Figure 3] The resulting difference in drag tends to yaw the airplane opposite to the direction of the turn. This is known as adverse yaw.

To counteract adverse yaw, the pilot applies rudder pressure in coordination with the aileron input. This produces a coordinated turn. Proper coordination is an important part of airplane control because sustained uncoordinated flight can increase the risk of a stall and spin, particularly at low altitudes, such as when operating in the airport traffic pattern.

During uncoordinated flight, the pilot may feel as though being pushed sideways toward the outside or inside of the turn. [Figure 4]

In a skid, the pilot feels pushed toward the outside of the turn; in a slip, the pilot feels pushed toward the inside. The ability to recognize slips and skids through the airplane’s feel develops with practice. Pilots should develop this awareness while also using appropriate flight instruments, such as the turn coordinator or slip-skid indicator, to verify coordination.

Turn Radius

To understand the relationship between airspeed, bank angle, and turn radius, it is important to recognize that the rate of turn depends on the horizontal component of lift. At a given airspeed, increasing the bank angle increases the horizontal component of lift and generally increases the rate of turn.

At a given bank angle, increasing airspeed generally decreases the rate of turn and increases the turn radius. This occurs because the airplane travels faster and requires a larger turning radius to follow its curved flightpath. [Figure 5]

As the radius of a turn decreases, a difference develops between the distances traveled by the inside and outside wings. The outside wing travels along a longer path than the inside wing, although both wings complete their respective paths in the same amount of time.

Therefore, the outside wing travels faster than the inside wing and may develop more lift. This contributes to an overbanking tendency that the pilot may need to control with opposite aileron pressure once the desired bank angle has been reached. [Figure 6]

The outside wing may also produce more drag, which can contribute to a tendency to slip during a steep turn. The pilot should maintain coordination using the rudder as necessary.

Establishing a Turn

On most light single-engine airplanes, the upper surface of the engine cowling is relatively flat. Its position relative to the natural horizon can provide a useful visual reference for initially establishing the desired bank angle. [Figure 7] The pilot should then cross-check the flight instruments to verify the bank angle. The attitude indicator shows the airplane’s bank attitude relative to the instrument’s horizon reference.

The pilot’s seating position is important because it affects the interpretation of outside visual references. A common problem is leaning away from the direction of the turn in an attempt to remain upright relative to the horizon. The pilot should maintain the normal seated position and use the airplane’s visual references rather than leaning to compensate for the bank. [Figure 8]

Because most airplanes have side-by-side seating, the pilot usually sits to one side of the airplane’s longitudinal axis. This offset can create a parallax effect and change the apparent position of the nose relative to the horizon during a turn. For example, the nose may appear to rise during a left turn and descend during a right turn because of the pilot’s position relative to the airplane’s roll axis. [Figure 9]

Pilots should recognize this effect and avoid making unnecessary pitch corrections based solely on the apparent movement of the nose.

Beginning pilots should avoid large aileron and rudder inputs when initiating a turn. Large inputs produce rapid roll rates and leave less time to evaluate the airplane’s response and make corrections. Smaller, smooth control inputs produce more manageable roll rates and allow the pilot more time to make accurate pitch and bank corrections.

Additional considerations when initiating turns include the following:

• If the airplane’s nose begins to move before the bank starts, rudder may have been applied too early or excessively.
• If the bank starts before the nose begins turning, or the nose moves in the opposite direction, the rudder may have been applied too late or insufficiently.
• If the nose moves noticeably up or down while the airplane enters the bank, the pilot may be applying excessive or insufficient elevator pressure.

After the desired bank angle has been established, the pilot should adjust the aileron and rudder pressures as necessary to maintain the turn. The required control pressures depend on the airplane’s stability characteristics, bank angle, and airspeed. In some airplanes, a shallow bank requires continued aileron pressure toward the turn, while a medium bank may require little aileron pressure. A steep turn may require opposite aileron pressure to prevent the bank angle from increasing. Rudder pressure should be adjusted as necessary to maintain coordination.

Elevator back pressure should be maintained as necessary to preserve the vertical component of lift and maintain altitude. Throughout the turn, the pilot should reference the natural horizon, scan for other aircraft, and occasionally cross-check the flight instruments to verify performance.

A reduction in airspeed may occur because of increased drag, although the effect may be small in shallow turns. In steeper turns, additional power may be needed to maintain airspeed. If the airplane is not maintaining altitude, the pilot should assess and correct the pitch attitude using outside visual references and cross-check the flight instruments to verify the result.

Steep turns require accurate, smooth, and timely control inputs. Minor pitch corrections are made with proportional elevator pressure while the desired bank angle is maintained with the ailerons. During steep turns, however, pilots may allow the nose to drop excessively, resulting in a rapid loss of altitude.

To recover from an excessively nose-low, steep-bank condition, the pilot should first reduce the bank angle using coordinated opposite aileron and rudder inputs, then adjust the pitch attitude with appropriate elevator pressure. Attempting to correct the condition using elevator alone can increase the bank angle and place unnecessary stress on the airplane. Appropriate power application can help overcome increased drag during steep turns. Depending on the airplane and the maneuver, trim may be used to reduce sustained elevator pressure, provided this is consistent with the airplane’s operating procedures.

Because the airplane continues turning while banked, the rollout should begin before the desired heading is reached. The amount of lead required depends on the bank angle and the airplane’s response. A common rule of thumb is to begin the rollout approximately one-half the bank angle before reaching the desired heading. For example, with a 30° bank, the pilot may begin the rollout about 15° before the desired heading.

The rollout is similar to the roll-in, except the pilot applies aileron and rudder in the opposite direction, toward the high wing. As the bank angle decreases, elevator pressure should be adjusted as necessary to maintain altitude. As the wings become level, the pilot should smoothly relax the control pressures and return to straight-and-level flight. If trim was used during the turn, additional control pressure may be required while the trim is readjusted. Throughout the rollout, the pilot should use outside visual references and cross-check the flight instruments to confirm that the wings are level and the turn has stopped.

Because the elevator and ailerons may be controlled by the same control stick or wheel, practice is necessary to ensure that pressure is applied to the intended control without unwanted inputs to another axis. For example, a beginning pilot may unintentionally change pitch when intending only to change bank. This cross-coupling depends partly on the design and arrangement of the flight controls and the pilot’s hand and arm movements.

With a stick control, moving the stick from the elbow rather than making a controlled wrist or arm movement may unintentionally introduce pitch changes while rolling. Depending on the control arrangement and the pilot’s technique, lowering the nose may also be accompanied by an unintended turn to the right, while raising the nose may be accompanied by an unintended turn to the left. These tendencies are not universal and depend on the control system and how the pilot moves it. Practice helps develop smooth, precise control inputs. The pilot should maintain an appropriate visual reference to the nose and natural horizon while isolating any unintended control movement.

Common Errors

Common errors in level turns include:

1. Failing to adequately clear the area in the direction of the turn for other aircraft.
2. Gaining or losing altitude during the turn.
3. Failing to maintain the desired bank angle.
4. Attempting to execute the turn solely by reference to flight instruments.
5. Leaning away from the direction of the turn while seated.
6. Having insufficient awareness of the airplane’s feel, as shown by an inability to detect slips or skids without relying entirely on flight instruments.
7. Attempting to maintain a constant bank angle by referring only to the airplane’s nose.
8. Making skidding, flat turns to avoid banking the airplane.
9. Holding excessive rudder pressure in the direction of the turn.
10. Developing proficiency in turns in only one direction.
11. Failing to coordinate the flight controls properly.