314 SCIENCE OF HOME AND COMMUNITY 



The direction of flight depends on the speed of the machine 

 and on the angle that the planes make with the direction 

 in which the machine is being driven. An increase in the 

 angle or in the speed tends to make the machine rise, a de- 

 crease to make it fall, so that by the proper adjustment of 

 speed and angle the machine may be made to go in a hori- 

 zontal plane. As the direction of the wind is constantly 

 changing, the aviator must change the angle of the planes 

 to correspond. 



Airplanes easily tip from side to side on account of the 

 variation in air currents on the two sides. This tendency 



FIG. 127. Seaplanj scout, a submarine chaser of the air. 



to tip must be neutralized in some way by the aviator. This 

 is most frequently done by warping the tips of the planes, or 

 through a motion of small flaps attached to the main planes. 

 These are controlled by means of a lever, which connects 

 with the tips by means of wires. They are so arranged that 

 as the tip on one side is warped up, the tip on the other side 

 is warped down. They can be so manipulated, as to check 

 the tendency of the machine to rock from side to side. 



In making a turn, the part of the machine on the outside 

 of the curve travels faster than the part on the inner side 

 and so tends to rise. This tendency is controlled by warping 

 the tips of the planes just as in keeping the machine balanced 

 in ordinary flight. In the first planes the aviator was ex- 



