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on or below the horizon to establish a specified airspeed. Any change in pitch attitude results in a change in airspeed. There is a pitch attitude reference for best glide speed, another for the minimum sink speed, and another for slow flight. The pitch attitude is adjusted with the elevator to hold the specific airspeed. The glider elevator trim control allows the pilot to trim the glider to hold a constant pitch attitude and, therefore, a constant airspeed. Straight glides should be coordinated as indicated by a centered yaw string or slip-skid ball. 

The glider pilot should also stay alert to airflow noise changes. At a constant airspeed in coordinated flight, wind noise should be constant. Any changes in airspeed or coordination cause a change in the wind noise. Gusts that cause the airspeed to change momentarily can be ignored. Holding the glider at a constant pitch attitude results in maintaining the desired airspeed control. 

The glider pilot should learn to fly throughout a wide range of airspeeds, from minimum controllable airspeed to maximum allowable airspeed. This enables the pilot to learn the feel of the controls of the glider throughout its speed range. If the glider is equipped with spoilers/dive brakes and/or flaps, the glider pilot should become familiar with the changes that occur in pitch attitude and airspeed when these controls are used. 

Common errors during straight glides include: 

• Rough or erratic pitch attitude and airspeed control. 

• Rough, uncoordinated, or inappropriate control applications. 

• Failure to use trim or improper use of trim. 

• Improper use of controls when using spoilers, dive brakes, and/or flaps. 

• Prolonged uncoordinated flight—yaw or ball not centered. 

## Turns 

The performance of turns involves coordination of all three flight controls: ailerons, rudder, and elevator. For purposes of this discussion, turns are divided into the following three classes as shown in Figure 7-29 . 

• Shallow turns are those in which the bank (less than approximately 20°) is so shallow that the inherent lateral stability of the glider levels the wings unless some aileron is applied to maintain the bank. 

• Medium turns are those resulting from a degree of bank (approximately 20° to 45°) at which lateral stability is overcome by the overbanking tendency, resulting in no control inputs (other than elevator) being required to maintain the angle. 

<img src='content_image/597409.jpg'>

• Steep turns are those resulting from a degree of bank (45° or more) at which the overbanking tendency of a glider overcomes stability, and the bank increases unless aileron is applied to prevent it. 

Before starting any turn, the pilot must clear the airspace in the direction of the turn. A glider is turned by banking (lowering the wing in the direction of the desired turn, thus raising the other). When the glider is flying straight, the total lift is acting perpendicular to the wings and to the earth. As the glider is banked into a turn, total lift becomes the resultant of two components: 1) the vertical lift component continues to act perpendicularly to the earth and opposes gravity and 2) 

