and airspeed. Speed should be allowed to dissipate before the  pitch attitude is decreased. This point is particularly important  for fast airplanes as they do not readily lose their airspeed— any slight deviation of the airplane’s nose downwards results  in an immediate increase in airspeed. Once the airspeed has  dissipated to best glide speed, the pitch attitude should be set  to maintain that airspeed. This should be done with reference  to the natural horizon and with a quick reference to the flight  instruments. When the airspeed has stabilized, the airplane  should be trimmed to eliminate any flight control pressures  held by the pilot. Precision is required in maintaining the best  glide airspeed if the benefits are to be realized.  at slow speeds.  With the absent propeller effects and the  subsequent  compensation for these effects, which is designed  into many airplanes, it is likely that, during glides, slight left  rudder pressure is required to maintain coordinated flight.  In addition, the deflection of the flight controls to effect  change is greater due to the relatively slow airflow over the  control surfaces. Minimum sink  speed is used to maximize the time that the  airplane remains in flight. It results in the airplane losing  altitude at the  lowest rate. Minimum sink speed occurs at an  airspeed less than the best glide speed. It is important that  pilots realize that flight at the minimum sink airspeed results  in less distance traveled. Minimum sink speed is useful in  flight situations where time in flight is more important than  distance flown. An example is ditching an airplane at sea.  Minimum sink speed is not an often published airspeed but  generally is a few knots less than best glide speed. In an emergency, such as an engine failure, attempting to  apply elevator back pressure to stretch a glide back to the  runway is likely to lead the airplane landing short and may  even lead to loss of control if the airplane stalls. This leads  to a cardinal rule of airplane flying that a student pilot must  understand and appreciate: The pilot must never attempt to  “stretch” a  glide by applying back-elevator pressure and  reducing the air speed below the airplane’s recommended best  glide speed. The purpose of pitch control during the glide is  to maintain the maximum L/D, which may require fore or  aft flight control pressure to maintain best glide airspeed.  To enter a glide, the pilot should close the throttle and,  if equipped, advance the propeller lever forward. With  back pressure on the elevator flight control, the pilot  should maintai n altitude until the airspeed decreases to  the recommended best glide speed. In most airplanes, as  power is reduced, propeller slipstream decreases over the  horizontal  stabil izer, which decreases the tail-down force,  and the airplane’s nose tends to lower immediately. To keep  pitch attitude  constant after a power change, the pilot must  counteract the  pitch down with a simultaneous increase in  elevator back pressure. If the pitch attitude is allowed to  decrease during glide entry, excess airspeed is carried into  the glide and retards the attainment of the correct glide angle  The absence of the propeller slipstream, loss of effectiveness  of the various flight control surfaces at lower airspeeds, and  designed-in aerodynamic corrections complicates the task of  flight control coordination in comparison to powered flight for  the inexperienced pilot. These principles should be thoroughly  explained by the flight instructor so that the beginner pilot  may be aware of the necessary differences in coordination.  Three elements in gliding turns that tend to force the nose  down and increase glide speed are: After a solid comprehension of the normal glide is attained,  the beginning pilot should be instructed in the differences  between normal and abnormal glides. Abnormal glides are  those glides conducted at speeds other than the best glide  speed. Glide airspeeds that are too slow or too fast may result  in the airplane not being able to make the intended landing  spot, flat approaches, hard touchdowns, floating, overruns,  and possibly stalls and an accident.  3-21 A stabilized, power-off descent at the best glide speed is  often referred to as normal glide. The beginning pilot should  memorize the airplane’s attitude and speed with reference  to the natural horizon and noting the sounds made by the  air passing over the airplane’s structure, forces on the flight  controls, and the feel of the airplane. Initially, the beginner  pilot may be unable to recognize slight variations in airspeed  and angle of bank by vision or by the pressure required on  the flight controls. The instructor should point out that an  increase in sound levels denotes increasing speed, while a  decrease in sound levels indicates decreasing speed. When  a sound level change is perceived, a beginning pilot should  cross-check the visual and pressure references. The beginning  pilot must use all three airspeed references (sound, visual,  and pressure) consciously until experience is gained, and then  must remain alert to any variation in attitude, feel, or sound. Figure 3-24.  Best glide speed provides the greatest forward distance  for a given loss of altitude. Gliding Turns • Decrease in lift due to the direction of the lifting force • Excessive rudder inputs as a result of reduced flight  control pressures 14 Too slow Too fast Best glide spee d