THE PLANE-DROPPER. 



35 



The actual mode of experiment with the inclined planes was to set the plane 

 at a given angle of elevation, for example 5°, and approximate to the critical 

 soaring speed by gradual variations of velocity, both above and below it. The 

 following extract from the note book shows the character of the record made in 

 executing this experiment : 



12x6 inch planes, inclined. 



18x4 inch planes, inclined. 



The detailed observations have already been given in Tables VI and VII 

 and the results are plotted in Figure 3, in which the ordinates are soaring speeds 

 and the abscissa? are the corresponding angles of inclination of the planes to the 

 horizon. This diagram shows that when set at an angle of 9° the 6 x 12 inch 

 plane requires a horizontal velocity of 21.2 meters per second to sustain it in the 

 air, while the 18 x 4 inch plane, set at the same angles, is supported by the air 

 when it is driven at a velocity of only 14 meters per second. The work to be 

 done in maintaining the flight at 14 meters per second is less than one-half that 

 for 21.2 meters per second, the angle remaining the same. 



These experiments enable us to make a first computation of the work expend.', 1 

 in horizontal flight. Let us, then, determine the horse-power required to drive 

 the two 18 x 4 inch planes horizontally in the air, when the planes are inclined 

 successively at 9° and at 5°. The work done per second is given by the product 

 R X V, E being the horizontal component of pressure on the plane, and V the 



