text: Thus, any pitching moment coefficient-re- 
  gardless of source-has 
  the common denomi- 
  nator of dynamic pressure, q, wing area, S, and 
  wing mean aerodynamic chord, MAC. This 
  common denominator is applied to the pitch- 
  ing moments contributed by the fuselage and 
  nacelles, horizontal 
  tail, and power effects 
  as well as pitching moments contributed by 
  the wing. 
  WING. 
  
  The contribution of the wing to 
  stability depends primarily on the location 
  of the aerodynamic center with respect to the 
  airplane center of gravity. Generally, 
  the 
  aerodynamic center-or a.c.-is defined as the 
  point on the wing mean aerodynamic chord 
  where the wing pitching moment coefficient 
  does not vary with lift coefficient. All changes 
  in lift coefficient effectively take place at the 
  wing aerodynamic center. Thus, if the wing 
  experiences some change in lift coefficient, the 
  pitching moment created will be a direct 
  function of the relative location of the a.c. and 
  c.g. 
  
  WhiIe the trim lift coefficient may be altered 
  the resulting 
  by a change in c.g. position, 
  change in stability is undesirable and is unsat- 
  isfactory as a primary means of control. The 
  variation of trim CL by deflection of control 
  surfaces is usually more effective and is less 
  inviting of disaster. The early attempts at 
  manned flight 
  Since stability 