by the yellow line. For sinking air, the starting point on the vertical scale has been moved up a distance corresponding to the vertical velocity of the air. Consequently, the red tangential line contacts the curve at a glide speed higher than best glide speed. 

Speed to fly depends on: 

1. The rate of climb the pilot expects to achieve in the next thermal or updraft. 

2. The rate of ascent or descent of the air mass through which the glider is flying. 

3. The glider’s inherent sink rate at all airspeeds between minimum-sink airspeed and never-exceed airspeed. 

4. Headwind or tailwind conditions. 

The object of speed to fly is to minimize the time and/or altitude required to fly from the current position to the next thermal and to minimize time in sink and maximize time in lift. Speed-to-fly information is presented to the pilot in one or more of the following ways: 

• By placing a speed-to-fly ring (MacCready ring) around the variometer dial. 

• Using the appropriate table or chart. 

• Using an electronic flight computer that displays the current optimum speed to fly. 

The pilot determines the speed to fly during initial planning and then constantly updates this information in flight. The pilot must be aware of changes in the flying conditions in order to be successful in conducting cross-country flights or during a soaring competition. 

Common errors regarding speed to fly are: 

• Improper determination of speed to fly. 

• Failure to maintain proper pitch attitude and airspeed control. 

• Not transitioning from cruise speed to climb speed in lift as needed and not changing to cruise speed when leaving lift in a prudent manner. 

