hausted, the required directional stability may 
be obtained by increases in tail area. How- 
ever, increased surface area has the obvious 
disadvantage of increased drag. 
The lift curve slope of the vertical tail 
relates how sensitive the surface is to changes 
in angle of attack. While it is desirable to 
have a high lift curve slope for the vertical 
surface, a high aspect ratio surface is not 
necessarily practical or desirable. The stall