text: nacelles deserves consideration in several in- 
  stances. Body upwash and variation of local 
  Mach number can influence the wing lift while 
  lift carryover and downwash can effect the fu- 
  selage and nacelles forces and moments. 
  
  of figure 4.7 illustrates the change of wing 
  contribution possible between subsonic and 
  supersonic flight. The large increase in static 
  in supersonic flight can incur high 
  stability 
  trim drag or require great control effectiveness 
  to prevent reduction in maneuverability. 
  
  In most 
  cases, the contribution of the fuselage and 
  nacelles is destabilizing. A symmetrical body 
  of revolution in the flow field of a perfect fluid 
  develops an unstable pitching moment when 
  given an angle of attack. 
  In fact, an increase 
  in angle of attack produces an increase in the 
  unstable pitching moment without 
  the devel- 
  Figure 4.8 illustrates the pres- 
  opment of lift. 
  sure distribution which creates this unstable 
  In the 
  moment on the body of revolution. 
  actual case of real subsonic flow essentially 
  the same effect is produced. An increase in 
  angle of attack causes an increase in 
  the 
  unstable pitching moment but a negligible 
  increase in lift. 
  
  FUSELAGE AND NACELLES. 