MILITARY AERONAUTICS SQUIER. 



139 



Table 1. — Computed power required to tow a plane 1 foot square xvcighing 1 

 pound JiorizontaUy through the air at various speeds and angles of flight. 



Column two, giving values of a for various speeds, is computed 

 from equation (1). Thus, at 30 miles per hour, 



W 



sma: 



2koAW 2 - 2 X .004 X 1 X 30^ 



whence a = 8.25°. 



Column three is computed from the term W tan a in equation (3), 

 thus: 



Drift = W tan a = 1 X tan 8.25° = 0.145. 



Column four is computed from the term 2/A in equation (3), 

 / l)eing taken from the skin-friction table, to be given presentl3\ 



The table shows that if a thin plane 1 foot square, weighing 1 pound, 

 be towed through the air so as just to float horizontally at various 

 velocities and angles of flight, the total resistance becomes a minimum 

 at an angle of slightly less than 3°, and at a velocity of about 50 miles 

 per hour; also that the skin-friction approximately equals the drift 

 at this angle. The table also shows that the propulsive power for the 

 given plane is a minimum at a speed of between 40 and 45 miles per 

 hour, the angle of flight then being approximately 4.5°. 



The last column of the table show^s that the maximum weight 

 carried per horsepower is less than 90 pounds. This horse load may 

 be increased by changing the foot-square plane to a rectangular plane 

 raid towing it long side foremost; also by lightening the load, and 

 letting the plane glide at a lower speed; but best of all, perhaps, by 

 arching it like a vulture's wing and also towing it long side foremost 

 as is the prevailing practice with aeroplanes. 



Stahility and control. 



The question of stability is a serious one in aviation, especially as 

 increased wind velocities are encountered. In machines of the aero- 



