68 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



\0L. 62 



Indeed, as in the case of lateral force Y, the effect of changes in A" 

 produced by the wing is of no account. 



On the other hand, L, the rolling moment produced as the wing is 

 yawed out of its course, is large and of the greatest importance, as it 



Fig. 29. 



interconnects directional and lateral stability. For a normal wing- 

 flying at any reasonable incidence a deviation from the course causes 

 a small rolling moment tending to bank the machine in a manner 

 appropriate to making the turn. The couple may be called a " natural 



