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186 U.S. CIVIL AERONAUTICS AUTHORITY starts to climb, ease the throttle open in order to maintain the speed as long as possible. The throttle is to be coordinated during the climb as was done in lazy eights and chandelles. The pressure on the elevators is constantly held and gradually increased as speed is lost to maintain the arc of the circle started as nearly as possible. The control pressure is coordinated with the loss of speed in a manner similar to that in chandelles. When the airplane has reached a partially inverted position, the pilot should throw his head back in order to check the nose as it passes the horizon and starts down and to see that its path will lead it directly toward the center of the road. After the nose has started well down past the horizon, the motor should be eased off by closing the throttle smoothly. This will help to prevent racing of the motor, excessive loss of altitude, excessive speed, and excessive loads during the recovery. The recovery from the dive should be made as quickly as possible consistent with speed and the maintaining of the arc of the loop as near as possible. As speed decreases during the recovery to level flight, ease the throttle open to normal cruising r. p. m. During the execution of the loop the rudder us used to keep the flight path in the true vertical plane and the ailerons are used to correct any tendency for a wing to be low in the normal manner. Many students have difficulties at the top of the loop, when the airplane is fully inverted. One of these is a tendency to hang there, which results in the occupants hanging on the safety belts ad the airplane falling out of the maneuver. This is due to insufficient initial speed, too rapid or sharp pull up at the start, or failure to properly coordinate the pressure on the stick with the decrease of properly coordinate the pressure on the stick with the decrease of speed. Other results may be falling inverted from some distance, an inverted spin, a normal spin, or merely some sort of slipshod recovery, depending on the use made of the controls during recovery efforts. Another difficulty is a persistent tendency to roll at the top of the loop. This is caused almost solely by the tendency of the pilot, when the head is thrown back at the top to judge the approach of the horizon, to pull the stick all the way back to get over the top in a hurry. In many airplanes this backward movement will start the roll immediately. However, in some it will have no effect. The flight path of the loop will probably never be a perfect circle due to the necessity for progressively shortening the radius of the turn to insure the airplane arriving at a position, under control, where gravity will aid in maintaining speed and in effecting recovery. For this reason the vertical diameter of the loop will be greater than the diameter parallel to the ground. The nearer these two diameters can be equalized the more near perfect the loop will be and the greater the degree of skill exhibited by the plot executing it. Correct judgment of the proper initial speed is of great assistance in making these diameters more nearly equal. The initial speed necessary is only determined by trial and error, and during the process, with strange airplane, considerable excess speed should be obtained for the first few performed. The excess speed can then be reduced as experience is gained and the airplane's
