NO. 3 



LANGLEY M KM oil; ON MECHANICAL FLIGHT 



49 



obtain by the decomposition of the force of gravity an elemenl g'k=W sin a 

 which acts in a direction parallel to the thrust-line. 



If we again neglect the horizontal hull resistance, equilibrium will he ob- 

 tained when 



kg'xag'=Txad' 

 or WRsvaa=TS 



, T8 



. -a = sin 



WB' 



a>\ 



Fig. 5. Diagram showing relation under certain conditions of thrust, C. P. and C. G. 



The practical application of these rules is greatly limited by the uncertainty 

 that attaches to the actual position of the center of pressure, and this fact and 

 also the numerical values involved may be illustrated by examples. 



Condition of Aerodrome No. 6, November 28, 1896 



The weight was 12.5 kilos. On November 28, the steam pressure was less 

 than 100 pounds, and the thrust may be taken at 4.5 kilos. The distance bd was 

 25 cm. 



Hence 12.5 xab =4.5x25 cm. 



ab = 9 cm. 



This appears to give the position of CP U but CP, is a resultant of the pressure on 

 both wings, and its position is determined by the empirical rule just cited. We 



